IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Introduction of semiconductor oxides in photovoltaic devicesMuhammad Mudassir
This document discusses the incorporation of semiconductor oxides in photovoltaic devices. It explains that semiconductor oxides like ZnO, TiO2, and SnO2 can absorb solar energy due to their band gap. These metal oxide semiconductors can be used as n-type or p-type materials in organic solar cells depending on their conduction and valence bands. The document also discusses how ZnO and TiO2 can be used as photocatalysts in applications like wastewater treatment due to their photoinduced oxidation-reduction reactions when illuminated. Finally, it states that metal oxide semiconductors are useful in technologies involving photon-assisted processes like serving as scaffold layers in dye-sensitized solar cells and transport layers
This document discusses photocatalysts, which are compounds that initiate or accelerate chemical reactions when activated by light. It provides examples of photocatalyst applications such as deodorization, antibacterial effects, water treatment, self-cleaning glass, water splitting to produce hydrogen, solar water disinfection, methane production from carbon monoxide, sterilization of surgical instruments, removal of fingerprints, decomposition of crude oil, and many others. The document explains that photocatalysts work by producing strong hydroxyl and oxygen radicals when activated by light that can destroy organic contaminants and convert them to harmless carbon dioxide and water.
Pawan Homogeneous catalyst for CO2 reductionPawan Kumar
This document provides an overview of homogenous photocatalytic reduction of CO2. It discusses key topics such as what photocatalysis is, problems with CO2 reduction, classifications of photocatalysts including homogeneous and heterogeneous examples, and mechanisms of type I and type II catalysts. Molecular complexes like rhenium and ruthenium are described as promising homogeneous photocatalysts. The effects of catalyst structure, reaction conditions, and anchoring to surfaces are reviewed. Future areas of improvement include increasing turnover numbers and standardizing test conditions for fair catalyst comparisons.
Photocatalysis uses light energy to facilitate chemical reactions. Photocatalysts generate holes and electrons when exposed to light that can oxidize or reduce organic matter, breaking it down into carbon dioxide and water. Photocatalysis has applications in renewable energy production like hydrogen fuel from water splitting and reducing carbon dioxide emissions. It can also degrade organic dyes and pollutants in wastewater via generation of radical species during photocatalyst excitation. In conclusion, photocatalysis shows promise as a green technology using sunlight for environmental and energy applications.
Visible light solar photocatalytic degradation of pulp and paper wastewater u...eSAT Journals
Abstract
With the growing number of industries there are large volumes of wastewater generated every day. Pulp and paper mills are highly polluting as they release effluents containing organic pollutants, and high levels of Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). Even though well-established processes exist to treat these effluents, there are only a few processes which are energy efficient. Conventional treatment methods are not effective for the degradation of toxic organic pollutants, hence other treatment techniques are necessary. One of the recent developments in this field is the Advanced Oxidation Process (AOP). Solar photocatalysis is a type of AOP which utilises UV light to activate semiconductor photocatalyst in order to produce highly reactive radical species. TiO2 is a widely used catalyst for this purpose, to oxidise or reduce the organic pollutants in industrial wastewater. However, photocatalysis using visible light has been receiving increased attention hence, modification of TiO2 is necessary for its enhanced response to visible light. There are many methods for modifying TiO2, such as doping and photo-sensitisation. This study focusses on the modification of TiO2 using the method of dye-sensitisation (photo-sensitisation) with the dyes rhodamine B and methylene blue. Solar photocatalytic experiments were carried out for the degradation of pulp and paper wastewater, at different conditions like varying catalyst loading (500mg, 600mg, 750mg and 1000mg of catalyst for 300ml of aqueous wastewater) and effluent concentration (20ml, 25ml, 30ml and 35ml of wastewater). Preliminary tests were done to determine the best conditions for photocatalytic degradation, and these were applied for final tests. Keywords - Solar Photocatalysis, Visible Light, Dye Sensitisation, Pulp and paper, Methylene blue, Rhodamine B, TiO2 catalyst.
1) Photocatalysis involves using light energy to facilitate chemical reactions. Photocatalysts like chlorophyll and titanium dioxide are able to breakdown organic matter into carbon dioxide and water when exposed to light.
2) Nanoparticles are necessary for high activity photocatalysts due to quantum size effects. Smaller nanoparticles have a larger surface area and better adsorption potential.
3) Photocatalysts have various applications including air purification by decomposing volatile organic compounds, self-cleaning surfaces, water purification by oxidizing pollutants, and dye degradation.
Nanophotocatalyst in organic transformationAshwani Dalal
This document discusses various types of nanophotocatalysts for organic transformations. It begins by explaining that chlorophyll is a natural photocatalyst that uses sunlight to convert water and carbon dioxide into oxygen and glucose. A photocatalyst uses light energy to facilitate chemical reactions by creating strong oxidizing agents and electronic holes that break down organic matter. For high photocatalytic activity, nanoparticles are necessary due to their small size and large surface area. Common types of nanophotocatalysts include semiconductor-based, plasmon-mediated, and metal-organic framework-based materials. The document then reviews literature on specific examples such as doped TiO2, CdS, composite semiconductors, and surface plasmon
Sunlight-driven water-splitting using two dimensional carbon based semiconduc...Pawan Kumar
The overwhelming challenge of depleting fossil fuels and anthropogenic carbon emissions has driven research
into alternative clean sources of energy. To achieve the goal of a carbon neutral economy, the harvesting of
sunlight by using photocatalysts to split water into hydrogen and oxygen is an expedient approach to fulfill
the energy demand in a sustainable way along with reducing the emission of greenhouse gases. Even though
the past few decades have witnessed intensive research into inorganic semiconductor photocatalysts, their
quantum efficiencies for hydrogen production from visible photons remain too low for the large scale
deployment of this technology. Visible light absorption and efficient charge separation are two key necessary
conditions for achieving the scalable production of hydrogen from water. Two-dimensional carbon based
nanoscale materials such as graphene oxide, reduced graphene oxide, carbon nitride, modified 2D carbon
frameworks and their composites have emerged as potential photocatalysts due to their astonishing
properties such as superior charge transport, tunable energy levels and bandgaps, visible light absorption,
high surface area, easy processability, quantum confinement effects, and high photocatalytic quantum yields.
The feasibility of structural and chemical modification to optimize visible light absorption and charge
separation makes carbonaceous semiconductors promising candidates to convert solar energy into chemical
energy. In the present review, we have summarized the recent advances in 2D carbonaceous photocatalysts
with respect to physicochemical and photochemical tuning for solar light mediated hydrogen evolution
Introduction of semiconductor oxides in photovoltaic devicesMuhammad Mudassir
This document discusses the incorporation of semiconductor oxides in photovoltaic devices. It explains that semiconductor oxides like ZnO, TiO2, and SnO2 can absorb solar energy due to their band gap. These metal oxide semiconductors can be used as n-type or p-type materials in organic solar cells depending on their conduction and valence bands. The document also discusses how ZnO and TiO2 can be used as photocatalysts in applications like wastewater treatment due to their photoinduced oxidation-reduction reactions when illuminated. Finally, it states that metal oxide semiconductors are useful in technologies involving photon-assisted processes like serving as scaffold layers in dye-sensitized solar cells and transport layers
This document discusses photocatalysts, which are compounds that initiate or accelerate chemical reactions when activated by light. It provides examples of photocatalyst applications such as deodorization, antibacterial effects, water treatment, self-cleaning glass, water splitting to produce hydrogen, solar water disinfection, methane production from carbon monoxide, sterilization of surgical instruments, removal of fingerprints, decomposition of crude oil, and many others. The document explains that photocatalysts work by producing strong hydroxyl and oxygen radicals when activated by light that can destroy organic contaminants and convert them to harmless carbon dioxide and water.
Pawan Homogeneous catalyst for CO2 reductionPawan Kumar
This document provides an overview of homogenous photocatalytic reduction of CO2. It discusses key topics such as what photocatalysis is, problems with CO2 reduction, classifications of photocatalysts including homogeneous and heterogeneous examples, and mechanisms of type I and type II catalysts. Molecular complexes like rhenium and ruthenium are described as promising homogeneous photocatalysts. The effects of catalyst structure, reaction conditions, and anchoring to surfaces are reviewed. Future areas of improvement include increasing turnover numbers and standardizing test conditions for fair catalyst comparisons.
Photocatalysis uses light energy to facilitate chemical reactions. Photocatalysts generate holes and electrons when exposed to light that can oxidize or reduce organic matter, breaking it down into carbon dioxide and water. Photocatalysis has applications in renewable energy production like hydrogen fuel from water splitting and reducing carbon dioxide emissions. It can also degrade organic dyes and pollutants in wastewater via generation of radical species during photocatalyst excitation. In conclusion, photocatalysis shows promise as a green technology using sunlight for environmental and energy applications.
Visible light solar photocatalytic degradation of pulp and paper wastewater u...eSAT Journals
Abstract
With the growing number of industries there are large volumes of wastewater generated every day. Pulp and paper mills are highly polluting as they release effluents containing organic pollutants, and high levels of Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). Even though well-established processes exist to treat these effluents, there are only a few processes which are energy efficient. Conventional treatment methods are not effective for the degradation of toxic organic pollutants, hence other treatment techniques are necessary. One of the recent developments in this field is the Advanced Oxidation Process (AOP). Solar photocatalysis is a type of AOP which utilises UV light to activate semiconductor photocatalyst in order to produce highly reactive radical species. TiO2 is a widely used catalyst for this purpose, to oxidise or reduce the organic pollutants in industrial wastewater. However, photocatalysis using visible light has been receiving increased attention hence, modification of TiO2 is necessary for its enhanced response to visible light. There are many methods for modifying TiO2, such as doping and photo-sensitisation. This study focusses on the modification of TiO2 using the method of dye-sensitisation (photo-sensitisation) with the dyes rhodamine B and methylene blue. Solar photocatalytic experiments were carried out for the degradation of pulp and paper wastewater, at different conditions like varying catalyst loading (500mg, 600mg, 750mg and 1000mg of catalyst for 300ml of aqueous wastewater) and effluent concentration (20ml, 25ml, 30ml and 35ml of wastewater). Preliminary tests were done to determine the best conditions for photocatalytic degradation, and these were applied for final tests. Keywords - Solar Photocatalysis, Visible Light, Dye Sensitisation, Pulp and paper, Methylene blue, Rhodamine B, TiO2 catalyst.
1) Photocatalysis involves using light energy to facilitate chemical reactions. Photocatalysts like chlorophyll and titanium dioxide are able to breakdown organic matter into carbon dioxide and water when exposed to light.
2) Nanoparticles are necessary for high activity photocatalysts due to quantum size effects. Smaller nanoparticles have a larger surface area and better adsorption potential.
3) Photocatalysts have various applications including air purification by decomposing volatile organic compounds, self-cleaning surfaces, water purification by oxidizing pollutants, and dye degradation.
Nanophotocatalyst in organic transformationAshwani Dalal
This document discusses various types of nanophotocatalysts for organic transformations. It begins by explaining that chlorophyll is a natural photocatalyst that uses sunlight to convert water and carbon dioxide into oxygen and glucose. A photocatalyst uses light energy to facilitate chemical reactions by creating strong oxidizing agents and electronic holes that break down organic matter. For high photocatalytic activity, nanoparticles are necessary due to their small size and large surface area. Common types of nanophotocatalysts include semiconductor-based, plasmon-mediated, and metal-organic framework-based materials. The document then reviews literature on specific examples such as doped TiO2, CdS, composite semiconductors, and surface plasmon
Sunlight-driven water-splitting using two dimensional carbon based semiconduc...Pawan Kumar
The overwhelming challenge of depleting fossil fuels and anthropogenic carbon emissions has driven research
into alternative clean sources of energy. To achieve the goal of a carbon neutral economy, the harvesting of
sunlight by using photocatalysts to split water into hydrogen and oxygen is an expedient approach to fulfill
the energy demand in a sustainable way along with reducing the emission of greenhouse gases. Even though
the past few decades have witnessed intensive research into inorganic semiconductor photocatalysts, their
quantum efficiencies for hydrogen production from visible photons remain too low for the large scale
deployment of this technology. Visible light absorption and efficient charge separation are two key necessary
conditions for achieving the scalable production of hydrogen from water. Two-dimensional carbon based
nanoscale materials such as graphene oxide, reduced graphene oxide, carbon nitride, modified 2D carbon
frameworks and their composites have emerged as potential photocatalysts due to their astonishing
properties such as superior charge transport, tunable energy levels and bandgaps, visible light absorption,
high surface area, easy processability, quantum confinement effects, and high photocatalytic quantum yields.
The feasibility of structural and chemical modification to optimize visible light absorption and charge
separation makes carbonaceous semiconductors promising candidates to convert solar energy into chemical
energy. In the present review, we have summarized the recent advances in 2D carbonaceous photocatalysts
with respect to physicochemical and photochemical tuning for solar light mediated hydrogen evolution
TiO2 and ZnO as Heterogeneous Photocatalysts for Wastewater TreatmentIRJET Journal
This document discusses the use of TiO2 and ZnO as heterogeneous photocatalysts for wastewater treatment. It begins with an introduction stating that industrial effluents cause environmental pollution and dyes from textile industries are toxic and difficult to degrade. It then provides details on the Z-scheme and heterojunction mechanisms for combining multiple photocatalysts to more effectively treat wastewater using solar light. The key advantages of these photocatalytic advanced oxidation processes are that they can mineralize organic pollutants under mild conditions and use solar energy.
Solar photocatalytic process & solar photocatalytic reactorsMuhammad Mudassir
This document discusses solar photocatalysis and solar photocatalytic reactors. It introduces photocatalysis as accelerating photoreactions using a catalyst and light. Titanium dioxide is commonly used as the photocatalyst due to its efficiency, stability, low cost and non-toxic properties. Solar photocatalytic reactors bring photons, photocatalyst and reactants into contact to produce reactions. The two main types are slurry reactors, which provide high surface area but require catalyst separation, and immobilized reactors, which don't require separation but have lower surface area. Applications include water treatment, sterilization and oil decomposition.
The document discusses photosynthesis and photocatalysis. It provides information on:
- Photosynthesis as a natural process that occurs in chloroplasts of plant cells and some bacteria, using light, water, carbon dioxide and producing oxygen, ATP, NADPH, and sugars through the Calvin cycle.
- Photocatalysis as using light to drive catalytic chemical reactions for energy needs, including producing fuels like hydrogen and cleaning environmental pollutants. Some examples of practical applications are provided.
- Both topics are further explained through diagrams of reaction processes, and literature on artificial photosynthesis and photoelectrochemical cells is referenced.
Water can be split into hydrogen and oxygen through various methods including electrolysis, photolysis, and photoelectrochemical water splitting. Water splitting produces hydrogen which can be used as a renewable fuel and reduces greenhouse gas emissions. Recent research has successfully used an artificial compound called Nafion to split water into hydrogen and oxygen through photoelectrochemical water splitting, demonstrating progress toward replicating natural photosynthesis and providing a clean energy source.
The threat of global warming is high due to the extensive use of fossil fuels.Using non-renewable resources is a viable solution. Sunlight can be converted in two ways - into electrical energy and into chemical energy. Water splitting and CO2 are two important methods which can be used in solar cells.
This document summarizes a presentation on misconceptions in photocatalysis given at the 15th Orientation Course on Catalysis in India in 2014. It discusses several common misconceptions in photocatalysis research, such as referring to photocatalysts as catalysts when photocatalysis involves accumulating energy rather than just lowering activation energy. It also addresses misconceptions around the role of hydroxyl radicals, use of dyes as model compounds, definitions of photocatalytic activity and synergetic effects, and mechanisms of hydrogen production via water splitting. Recommended reading materials provide further details on the topics covered.
Polymeric carbon nitride-based photocatalysts for photoreforming of biomass d...Pawan Kumar
Photoreforming of biomass to value-added chemicals and fuels is a chemical approach to extract photosynthetically-trapped energy in complex biomolecules which otherwise disintegrate naturally in the environment. Designing precise photocatalytic materials that can selectively break the sturdy, nature-designed biomass with multiplex chemical composition/bonding and inaccessible sites is central to deploying this technology. Polymeric carbon nitride (CN) comprised of a 2D network of condensed heptazine/triazine (C6N7/C3N3) core has shown great promise for photoreforming of biomass derivatives due to intriguing physicochemical and optical properties. This review comprehensively summarizes the state-of-the-art applications of CN-based photocatalysts for the conversion of lignocellulosic biomass derivatives. Various chemical and structural modifications in CN structure such as doping, surface functionalization, hybridization entailing to higher selectivity and conversion have been discussed aiming at providing valuable guidance for future CN-based materials design.
Roll of nanomaterials in water treatment as photocatalysts copyUsama Ismail
This document summarizes research on using nanomaterials as photocatalysts for water treatment. It discusses how nanoparticles have unique properties that make them effective photocatalysts. Several studies are highlighted that synthesized different nanocomposites for degrading organic dyes and pollutants in water under visible light, including ZnCdS nanoparticles on reduced graphene oxide, graphene-gold nanocomposites, and graphene composites with SnO2 and TiO2. These nanocomposites showed enhanced photocatalytic activity compared to their individual components for degrading dyes like Rhodamine B under visible light irradiation.
ICWES15 - Preparation of Mesoporous Titania Photocatalyst for Water Treatment...Engineers Australia
The document summarizes research into preparing mesoporous titania photocatalysts for water treatment applications. Key points include:
1) Titania has a wide band gap limiting photocatalysis to UV light and high electron-hole recombination rates, which the research aims to address.
2) The research involves controlling titania's composition, crystal phase, morphology through preparation methods to enhance photocatalytic activity under visible light.
3) Preliminary results found the porous titania prepared at pH 7.98 showed highest adsorption capacity while the sample at pH 11.58 exhibited maximum photocatalytic activity.
This document discusses photocatalytic water purification technology. It explains that photocatalysis uses a semiconductor like titanium dioxide to create electron-hole pairs when exposed to light, which can then carry out oxidation and reduction reactions to break down pollutants in water. The most commonly used semiconductor is titanium dioxide because it is non-toxic. This technology has applications in water treatment plants and for degrading chemicals in wastewater from textile factories. It can also be used to treat water-soluble pesticides.
Sunlight induced removal of Rhodamine B from water through Semiconductor Pho...Hariprasad Narayanan
This document summarizes research on the photocatalytic removal of Rhodamine B dye from water using TiO2 and platinum-deposited TiO2 (Pt/TiO2) under sunlight and UV light. Key findings include:
1) Pt/TiO2 showed around 5 times higher activity than TiO2 alone for degrading Rhodamine B under sunlight, due to Pt extending TiO2's absorption into the visible light range and reducing electron-hole recombination.
2) Over 80% of Rhodamine B was degraded within 4 hours using Pt/TiO2 under sunlight, compared to only around 20% for TiO2 alone.
3) The optimum catalyst loading was 0.1 g/L for
Nanostructured composite materials for CO2 activationPawan Kumar
This document discusses nanostructured composite materials for CO2 activation, specifically for the photocatalytic reduction of CO2 to valuable products. It provides background on the increasing energy crisis and climate change caused by fossil fuel use. It then summarizes the basic principles and challenges of using semiconductor photocatalysts for CO2 reduction, including appropriate band gap positions and preventing electron-hole recombination. The document discusses various approaches to overcoming these challenges, such as forming heterojunction composites and using co-catalysts to facilitate charge separation and transfer.
HYDROGEN GENERATION FROM WASTE WATER BY USING SOLAR ENERGY | J4RV3I11004Journal For Research
Objective of this paper is to produce hydrogen which is an ideal fuel for the next generation because it is abundantly available in nature, energy efficient and clean. Wide varieties of technologies are available to produce hydrogen but only few of them are considered environmental friendly. Solar water splitting via photo catalytic reaction is one of them which have attracted tremendous attention. In this paper we are working on hydrogen production via solar splitting. Photo catalytic water splitting is one of the promising technologies to produce pure and clean hydrogen. Since it is reasonable having low process cost and has a small reactor, it can be made for house hold application and hence has a huge market potential. Generation of hydrogen under visible irradiation is the main area of work. Based on the literature reported here, visible irradiation can be achieved by doping of TiO2 with metal or non-metal. We have used Fe doping to increase the efficiency. The result indicates that Fe doped sieves produce more hydrogen than the normal TiO2 coated sieve and the efficiency can be increased if we increase the number of doped sieves and surface area.
Solar Photocatalysis a green and novel technology for wastewater treatment. It is a sustainable way to harvest solar energy for treatment of wastewater at a lower cost thus helping in achieving some of the Sustainable Development Goals(i.e. Good Health and Wellbeing).
This is based on the advanced oxidation process i.e. generation of reactive oxygen species which can help in the degradation of pollutants
Bicrystalline Titania Photocatalyst for Reduction of CO2 to Solar FuelsA'Lester Allen
Degussa P25, a mixture of anatase and rutile crystal structures, is the most commonly used precursor to form the photoactive layer in solar cells; however, the photocatalytic activity of rutile is inferior to brookite. This presentation discusses the enhancement in photocatalytic activity of an antase brookite mixture.
This document is a resume for Dr. Elena A. Guliants seeking a research or program management position involving renewable and alternative energy technologies. She has over 23 years of experience in fields such as photovoltaics, energy storage, hydrogen generation, and nanoenergetics. Her educational background includes a Ph.D. in Electrical Engineering and an M.B.A. She is fluent in English and Russian.
Recent advances in photocatalytic reactors were summarized in 3 sentences or less:
The document reviewed various photocatalytic reactor designs used to degrade organic pollutants like pesticides and dyes, as well as microorganisms, using different catalysts like TiO2 and light sources like sunlight and UV lamps. Reactors included batch, continuous flow, and thin film designs. Degradation rates of over 90% were typically achieved for various contaminants like monocrotophos, acetamiprid, thiabendazole, methyl orange, and rhodamine B.
TiO2-HfN Radial Nano-Heterojunction: A Hot Carrier Photoanode for Sunlight-Dr...Pawan Kumar
The lack of active, stable, earth-abundant, and visible-light absorbing materials to replace
plasmonic noble metals is a critical obstacle for researchers in developing highly efficient and costeffective photocatalytic systems. Herein, a core–shell nanotube catalyst was fabricated consisting of
atomic layer deposited HfN shell and anodic TiO2 support layer with full-visible regime photoactivity
for photoelectrochemical water splitting. The HfN active layer has two unique characteristics: (1) a
large bandgap between optical and acoustic phonon modes (2) and no electronic bandgap, which
allows a large population of long life-time hot carriers, which are used to enhance the photoelectrochemical performance. The photocurrent density (≈2.5 mA·cm−2 at 1 V vs. Ag/AgCl) obtained in
this study under AM 1.5G 1 Sun illumination is unprecedented, as it is superior to most existing
plasmonic noble metal-decorated catalysts and surprisingly indicates a photocurrent response that
extends to 730 nm. The result demonstrates the far-reaching application potential of replacing active
HER/HOR noble metals such as Au, Ag, Pt, Pd, etc. with low-cost plasmonic ceramics.
This document discusses photoelectrochemical water splitting for hydrogen production. It describes the process which uses a photoelectrode to drive the oxidation of water at the anode and the concurrent reduction of protons at the cathode to produce hydrogen gas. Issues with the technology include high costs of production compared to natural gas, slow oxygen evolution kinetics, and challenges associated with transporting and storing the gases produced. The document then reviews current research trends focused on developing new photoelectrode materials like metal oxides, improving material morphologies at the nano-scale, and investigating techniques like electrospinning to produce novel structures with improved performance.
The document describes the synthesis and morphology of silicon nanoparticles deposited on a silicon dioxide substrate using low pressure chemical vapor deposition with varying deposition times. Atomic force microscopy and image analysis software were used to characterize the nanoparticles and found that their height, density, and size varied with deposition time, with heights between 1-3 nm, densities from 2x1011 to 3.5x1011 particles/cm2, and sizes of 2-10 nm. The goal was to study how the morphological and electrical characteristics of the nanoparticles changed with different deposition parameters.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
TiO2 and ZnO as Heterogeneous Photocatalysts for Wastewater TreatmentIRJET Journal
This document discusses the use of TiO2 and ZnO as heterogeneous photocatalysts for wastewater treatment. It begins with an introduction stating that industrial effluents cause environmental pollution and dyes from textile industries are toxic and difficult to degrade. It then provides details on the Z-scheme and heterojunction mechanisms for combining multiple photocatalysts to more effectively treat wastewater using solar light. The key advantages of these photocatalytic advanced oxidation processes are that they can mineralize organic pollutants under mild conditions and use solar energy.
Solar photocatalytic process & solar photocatalytic reactorsMuhammad Mudassir
This document discusses solar photocatalysis and solar photocatalytic reactors. It introduces photocatalysis as accelerating photoreactions using a catalyst and light. Titanium dioxide is commonly used as the photocatalyst due to its efficiency, stability, low cost and non-toxic properties. Solar photocatalytic reactors bring photons, photocatalyst and reactants into contact to produce reactions. The two main types are slurry reactors, which provide high surface area but require catalyst separation, and immobilized reactors, which don't require separation but have lower surface area. Applications include water treatment, sterilization and oil decomposition.
The document discusses photosynthesis and photocatalysis. It provides information on:
- Photosynthesis as a natural process that occurs in chloroplasts of plant cells and some bacteria, using light, water, carbon dioxide and producing oxygen, ATP, NADPH, and sugars through the Calvin cycle.
- Photocatalysis as using light to drive catalytic chemical reactions for energy needs, including producing fuels like hydrogen and cleaning environmental pollutants. Some examples of practical applications are provided.
- Both topics are further explained through diagrams of reaction processes, and literature on artificial photosynthesis and photoelectrochemical cells is referenced.
Water can be split into hydrogen and oxygen through various methods including electrolysis, photolysis, and photoelectrochemical water splitting. Water splitting produces hydrogen which can be used as a renewable fuel and reduces greenhouse gas emissions. Recent research has successfully used an artificial compound called Nafion to split water into hydrogen and oxygen through photoelectrochemical water splitting, demonstrating progress toward replicating natural photosynthesis and providing a clean energy source.
The threat of global warming is high due to the extensive use of fossil fuels.Using non-renewable resources is a viable solution. Sunlight can be converted in two ways - into electrical energy and into chemical energy. Water splitting and CO2 are two important methods which can be used in solar cells.
This document summarizes a presentation on misconceptions in photocatalysis given at the 15th Orientation Course on Catalysis in India in 2014. It discusses several common misconceptions in photocatalysis research, such as referring to photocatalysts as catalysts when photocatalysis involves accumulating energy rather than just lowering activation energy. It also addresses misconceptions around the role of hydroxyl radicals, use of dyes as model compounds, definitions of photocatalytic activity and synergetic effects, and mechanisms of hydrogen production via water splitting. Recommended reading materials provide further details on the topics covered.
Polymeric carbon nitride-based photocatalysts for photoreforming of biomass d...Pawan Kumar
Photoreforming of biomass to value-added chemicals and fuels is a chemical approach to extract photosynthetically-trapped energy in complex biomolecules which otherwise disintegrate naturally in the environment. Designing precise photocatalytic materials that can selectively break the sturdy, nature-designed biomass with multiplex chemical composition/bonding and inaccessible sites is central to deploying this technology. Polymeric carbon nitride (CN) comprised of a 2D network of condensed heptazine/triazine (C6N7/C3N3) core has shown great promise for photoreforming of biomass derivatives due to intriguing physicochemical and optical properties. This review comprehensively summarizes the state-of-the-art applications of CN-based photocatalysts for the conversion of lignocellulosic biomass derivatives. Various chemical and structural modifications in CN structure such as doping, surface functionalization, hybridization entailing to higher selectivity and conversion have been discussed aiming at providing valuable guidance for future CN-based materials design.
Roll of nanomaterials in water treatment as photocatalysts copyUsama Ismail
This document summarizes research on using nanomaterials as photocatalysts for water treatment. It discusses how nanoparticles have unique properties that make them effective photocatalysts. Several studies are highlighted that synthesized different nanocomposites for degrading organic dyes and pollutants in water under visible light, including ZnCdS nanoparticles on reduced graphene oxide, graphene-gold nanocomposites, and graphene composites with SnO2 and TiO2. These nanocomposites showed enhanced photocatalytic activity compared to their individual components for degrading dyes like Rhodamine B under visible light irradiation.
ICWES15 - Preparation of Mesoporous Titania Photocatalyst for Water Treatment...Engineers Australia
The document summarizes research into preparing mesoporous titania photocatalysts for water treatment applications. Key points include:
1) Titania has a wide band gap limiting photocatalysis to UV light and high electron-hole recombination rates, which the research aims to address.
2) The research involves controlling titania's composition, crystal phase, morphology through preparation methods to enhance photocatalytic activity under visible light.
3) Preliminary results found the porous titania prepared at pH 7.98 showed highest adsorption capacity while the sample at pH 11.58 exhibited maximum photocatalytic activity.
This document discusses photocatalytic water purification technology. It explains that photocatalysis uses a semiconductor like titanium dioxide to create electron-hole pairs when exposed to light, which can then carry out oxidation and reduction reactions to break down pollutants in water. The most commonly used semiconductor is titanium dioxide because it is non-toxic. This technology has applications in water treatment plants and for degrading chemicals in wastewater from textile factories. It can also be used to treat water-soluble pesticides.
Sunlight induced removal of Rhodamine B from water through Semiconductor Pho...Hariprasad Narayanan
This document summarizes research on the photocatalytic removal of Rhodamine B dye from water using TiO2 and platinum-deposited TiO2 (Pt/TiO2) under sunlight and UV light. Key findings include:
1) Pt/TiO2 showed around 5 times higher activity than TiO2 alone for degrading Rhodamine B under sunlight, due to Pt extending TiO2's absorption into the visible light range and reducing electron-hole recombination.
2) Over 80% of Rhodamine B was degraded within 4 hours using Pt/TiO2 under sunlight, compared to only around 20% for TiO2 alone.
3) The optimum catalyst loading was 0.1 g/L for
Nanostructured composite materials for CO2 activationPawan Kumar
This document discusses nanostructured composite materials for CO2 activation, specifically for the photocatalytic reduction of CO2 to valuable products. It provides background on the increasing energy crisis and climate change caused by fossil fuel use. It then summarizes the basic principles and challenges of using semiconductor photocatalysts for CO2 reduction, including appropriate band gap positions and preventing electron-hole recombination. The document discusses various approaches to overcoming these challenges, such as forming heterojunction composites and using co-catalysts to facilitate charge separation and transfer.
HYDROGEN GENERATION FROM WASTE WATER BY USING SOLAR ENERGY | J4RV3I11004Journal For Research
Objective of this paper is to produce hydrogen which is an ideal fuel for the next generation because it is abundantly available in nature, energy efficient and clean. Wide varieties of technologies are available to produce hydrogen but only few of them are considered environmental friendly. Solar water splitting via photo catalytic reaction is one of them which have attracted tremendous attention. In this paper we are working on hydrogen production via solar splitting. Photo catalytic water splitting is one of the promising technologies to produce pure and clean hydrogen. Since it is reasonable having low process cost and has a small reactor, it can be made for house hold application and hence has a huge market potential. Generation of hydrogen under visible irradiation is the main area of work. Based on the literature reported here, visible irradiation can be achieved by doping of TiO2 with metal or non-metal. We have used Fe doping to increase the efficiency. The result indicates that Fe doped sieves produce more hydrogen than the normal TiO2 coated sieve and the efficiency can be increased if we increase the number of doped sieves and surface area.
Solar Photocatalysis a green and novel technology for wastewater treatment. It is a sustainable way to harvest solar energy for treatment of wastewater at a lower cost thus helping in achieving some of the Sustainable Development Goals(i.e. Good Health and Wellbeing).
This is based on the advanced oxidation process i.e. generation of reactive oxygen species which can help in the degradation of pollutants
Bicrystalline Titania Photocatalyst for Reduction of CO2 to Solar FuelsA'Lester Allen
Degussa P25, a mixture of anatase and rutile crystal structures, is the most commonly used precursor to form the photoactive layer in solar cells; however, the photocatalytic activity of rutile is inferior to brookite. This presentation discusses the enhancement in photocatalytic activity of an antase brookite mixture.
This document is a resume for Dr. Elena A. Guliants seeking a research or program management position involving renewable and alternative energy technologies. She has over 23 years of experience in fields such as photovoltaics, energy storage, hydrogen generation, and nanoenergetics. Her educational background includes a Ph.D. in Electrical Engineering and an M.B.A. She is fluent in English and Russian.
Recent advances in photocatalytic reactors were summarized in 3 sentences or less:
The document reviewed various photocatalytic reactor designs used to degrade organic pollutants like pesticides and dyes, as well as microorganisms, using different catalysts like TiO2 and light sources like sunlight and UV lamps. Reactors included batch, continuous flow, and thin film designs. Degradation rates of over 90% were typically achieved for various contaminants like monocrotophos, acetamiprid, thiabendazole, methyl orange, and rhodamine B.
TiO2-HfN Radial Nano-Heterojunction: A Hot Carrier Photoanode for Sunlight-Dr...Pawan Kumar
The lack of active, stable, earth-abundant, and visible-light absorbing materials to replace
plasmonic noble metals is a critical obstacle for researchers in developing highly efficient and costeffective photocatalytic systems. Herein, a core–shell nanotube catalyst was fabricated consisting of
atomic layer deposited HfN shell and anodic TiO2 support layer with full-visible regime photoactivity
for photoelectrochemical water splitting. The HfN active layer has two unique characteristics: (1) a
large bandgap between optical and acoustic phonon modes (2) and no electronic bandgap, which
allows a large population of long life-time hot carriers, which are used to enhance the photoelectrochemical performance. The photocurrent density (≈2.5 mA·cm−2 at 1 V vs. Ag/AgCl) obtained in
this study under AM 1.5G 1 Sun illumination is unprecedented, as it is superior to most existing
plasmonic noble metal-decorated catalysts and surprisingly indicates a photocurrent response that
extends to 730 nm. The result demonstrates the far-reaching application potential of replacing active
HER/HOR noble metals such as Au, Ag, Pt, Pd, etc. with low-cost plasmonic ceramics.
This document discusses photoelectrochemical water splitting for hydrogen production. It describes the process which uses a photoelectrode to drive the oxidation of water at the anode and the concurrent reduction of protons at the cathode to produce hydrogen gas. Issues with the technology include high costs of production compared to natural gas, slow oxygen evolution kinetics, and challenges associated with transporting and storing the gases produced. The document then reviews current research trends focused on developing new photoelectrode materials like metal oxides, improving material morphologies at the nano-scale, and investigating techniques like electrospinning to produce novel structures with improved performance.
The document describes the synthesis and morphology of silicon nanoparticles deposited on a silicon dioxide substrate using low pressure chemical vapor deposition with varying deposition times. Atomic force microscopy and image analysis software were used to characterize the nanoparticles and found that their height, density, and size varied with deposition time, with heights between 1-3 nm, densities from 2x1011 to 3.5x1011 particles/cm2, and sizes of 2-10 nm. The goal was to study how the morphological and electrical characteristics of the nanoparticles changed with different deposition parameters.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
A novel methodology for test scenario generation based on control flow analys...eSAT Publishing House
This document presents a novel methodology for generating test scenarios from UML 2.x sequence diagrams. It proposes constructing an intermediate control flow graph called a Sequence Control Flow Graph (SCFG) by analyzing the control flow in UML sequence diagrams. It also proposes a test scenario generation algorithm called STSGA that systematically generates test scenarios from the SCFG to test software in the early design phase and help testers later in the development cycle. The approach aims to address the challenges of fragments like alt, loop, break, par, and opt in UML sequence diagrams.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Analysis of mhd non darcian boundary layer flow and heat transfer over an exp...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Online social network mining current trends and research issueseSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Design and development of non server peer 2 peer secure communication using j...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
This document discusses various privacy preservation techniques in data mining. It summarizes classification, clustering, and association rule learning as common privacy preservation approaches. For classification, it describes decision trees, k-nearest neighbors, artificial neural networks, support vector machines, and naive Bayes models. It provides advantages and disadvantages of these techniques. The document concludes that privacy preservation techniques have emerged to allow for efficient and effective data mining while protecting sensitive data.
Comparative studies on flotation of kasolite using cationic and anionic surfa...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
The document summarizes research on the effect of concentration on the structural and optical properties of copper sulfide (CuS) thin films deposited using chemical bath deposition. Thin films were deposited on glass substrates from aqueous solutions containing different concentrations of copper sulfate (0.05M to 0.15M). Scanning electron microscopy and atomic force microscopy images showed that films deposited at 0.1M copper concentration had a uniform, compact, and homogeneous structure, while higher concentrations resulted in non-uniform and unstable films. Absorbance, transmittance, and band gap measurements showed the optical properties varied with concentration. X-ray diffraction patterns indicated crystallinity depended on copper concentration in the bath solution.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
This document summarizes a research paper that proposes a novel approach for securing data by combining steganography and extended visual cryptography. It involves three main steps: 1) Hidden data is embedded into a cover image using a text embedding algorithm. 2) The cover image is then encrypted into two shares using a visual cryptography technique called VIP synchronization and error diffusion. 3) To extract the hidden data, the shares are combined and the extraction algorithm retrieves the text from the pixel values. The approach generates meaningful shares that look like random noise images. It analyzes the results by calculating the PSNR and MSE values between the original cover images and generated shares.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
This document discusses hydrogen production from photocatalytic water splitting using semiconductor materials. It begins by introducing alternative energies and hydrogen as an ideal fuel. It then discusses various methods of hydrogen production, focusing on solar-driven processes like thermochemical, photobiological, and photocatalytic water splitting. The document examines using titanium dioxide (TiO2) as a photocatalyst for water splitting and methods to improve its photoactivity, such as metal loading and doping. It also discusses high-efficiency photocatalytic systems and the types of photocatalytic water splitting reactions. In the end, it emphasizes the need for further research to develop new technologies for low-cost, environmentally friendly hydrogen production.
Arrays of TiO2 nanorods embedded with fluorine doped carbon nitride quantum d...Pawan Kumar
Graphenic semiconductors such as carbon nitride are attracting increasing attention as photocatalysts due to their chemical stability, visible light absorption and excellent electronic properties. The photocatalytic activity of nanostructured TiO2 catalysts is constrained by the wide bandgap and concomitant low visible light responsivity of TiO2. In this context we present the formation of new fluorine doped carbon nitride quantum dots (CNFQDs) by solid state reaction and the subsequent examination of their heterojunctions with TiO2 for photoelectrochemical water splitting. Arrays of rutile phase TiO2 nanorods embedded with CNFQDs were synthesized by a simple in situ hydrothermal approach and the resulting nanomaterials were found to exhibit strong visible light absorption. The energetics at the heterojunction were favorable for efficient electron transfer from CNFQDs to TiO2 under visible light irradiation and …
Arrays of TiO2 nanorods embedded with fluorine doped carbon nitride quantum d...Pawan Kumar
Graphenic semiconductors such as carbon nitride are attracting increasing attention as photocatalysts due to their chemical stability, visible light absorption and excellent electronic properties. The photocatalytic activity of nanostructured TiO2 catalysts is constrained by the wide bandgap and concomitant low visible light responsivity of TiO2. In this context we present the formation of new fluorine doped carbon nitride quantum dots (CNFQDs) by solid state reaction and the subsequent examination of their heterojunctions with TiO2 for photoelectrochemical water splitting. Arrays of rutile phase TiO2 nanorods embedded with CNFQDs were synthesized by a simple in situ hydrothermal approach and the resulting nanomaterials were found to exhibit strong visible light absorption. The energetics at the heterojunction were favorable for efficient electron transfer from CNFQDs to TiO2 under visible light irradiation and transfer of holes to the aqueous electrolyte. CNFQD-sensitized TiO2 nanorods exhibited a strong photoelectrochemical response up to 500 nm. Reuse experiments confirmed robustness and long term stability of the sample without exhausting the catalytic performance. The present work demonstrates a new pathway to sensitize TiO2 to visible photons by the in situ formation of embedded heterojunctions with fluorine doped carbon nitride quantum dots
Photocatalytic decomposition of isolan black by tio2, tio2 sio2 core shell na...eSAT Journals
Abstract Anatase phase TiO2, TiO2-SiO2 (TS) photocatalyst were prepared by wet chemical technique. The synthesized nano particles were characterized by XRD, SEM-EDAX, TEM, UV and FTIR spectroscopy. The grain size of the TiO2 nanoparticles was found to be 24nm, while 7-10nm for TiO2-SiO2was calculated by using Scherrer’s formula. The TiO2-SiO2 core shell nanocomposites were identified by TEM analysis. Ti-O, Si-O bonds were confirmed by EDAX and FTIR. The photocatalytic decomposition of Isolan black was investigated. The photo catalytic activity of TiO2, enhanced by doping of SiO2 on TiO2. The important factors such as pH, Wt % of dyes and nanoparticles, intensity of light are also affect the photocatalytic action. Index Terms: Nanocomposites, Photocatalyst, TEM, SEM-EDAX.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
This research summary describes the work of Yong-Siou Chen focusing on developing nanomaterials for efficient light energy conversion applications. Two major projects are described: (1) Using thiolate-protected gold nanoclusters as a new class of photosensitizer for solar cells and hydrogen production from water splitting, achieving higher efficiencies than existing technologies. (2) Designing a tandem device using bismuth vanadate and lead halide perovskite solar cells for bias-free hydrogen production from water splitting under sunlight. The work establishes new nanomaterials and device architectures for clean, cost-effective electricity and hydrogen generation.
Vapor Deposition of Semiconducting Phosphorus Allotropes into TiO2 Nanotube A...Pawan Kumar
Recent evidence of exponential environmental degradation will demand a drastic shift in research and development toward
exploiting alternative energy resources such as solar energy. Here, we
report the successful low-cost and easily accessible synthesis of hybrid
semiconductor@TiO2 nanotube photocatalysts. In order to realize its
maximum potential in harvesting photons in the visible-light range, TiO2
nanotubes have been loaded with earth-abundant, low-band-gap fibrous
red and black phosphorus (P). Scanning electron microscopy− and
scanning transmission electron microscopy−energy-dispersive X-ray
spectroscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron microscopy, and UV−vis measurements have been performed,
substantiating the deposition of fibrous red and black P on top and
inside the cavities of 100-μm-long electrochemically fabricated nanotubes. The nanotubular morphology of titania and a vapor-transport technique are utilized to form heterojunctions of P and
TiO2. Compared to pristine anatase 3.2 eV TiO2 nanotubes, the creation of heterojunctions in the hybrid material resulted in
1.5−2.1 eV photoelectrocatalysts. An enhanced photoelectrochemical water-splitting performance under visible light compared
with the individual components resulted for the P@TiO2 hybrids. This feature is due to synergistically improved charge
separation in the heterojunction and more effective visible-light absorption. The electronic band structure and charge-carrier
dynamics are investigated in detail using ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy to elucidate
the charge-separation mechanism. A Fermi-level alignment in P@TiO2 heterojunctions leads to a more reductive flat-band
potential and a deeper valence band compared to pristine P and thus facilitates a better water-splitting performance. Our results
demonstrate effective conversion efficiencies for the nanostructured hybrids, which may enable future applications in
optoelectronic applications such as photodetectors, photovoltaics, photoelectrochemical catalysts, and sensors.
Vapor Deposition of Semiconducting Phosphorus Allotropes into TiO2 Nanotube A...Pawan Kumar
Recent evidence of exponential environmental degradation will demand a drastic shift in research and development toward exploiting alternative energy resources such as solar energy. Here, we report the successful low-cost and easily accessible synthesis of hybrid semiconductor@TiO2 nanotube photocatalysts. In order to realize its maximum potential in harvesting photons in the visible-light range, TiO2 nanotubes have been loaded with earth-abundant, low-band-gap fibrous red and black phosphorus (P). Scanning electron microscopy– and scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron microscopy, and UV–vis measurements have been performed, substantiating the deposition of fibrous red and black P on top and inside the cavities of 100-μm-long electrochemically fabricated nanotubes. The nanotubular …
This document summarizes a research paper on dye sensitized solar cells (DSSCs). It provides background on the development of DSSCs since 1991 and their advantages over traditional silicon solar cells in terms of lower cost and simpler preparation. However, liquid electrolytes used in early DSSCs limited long-term performance. Recent research has focused on improving electrolytes, particularly developing quasi-solid state electrolytes, to enhance photoelectric performance and stability for practical applications of DSSCs. The document reviews progress on quasi-solid state electrolytes and their advantages over liquid electrolytes for DSSCs.
Vapor growth of binary and ternary phosphorus-based semiconductors into TiO 2...Pawan Kumar
We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP …
High rate CO2 photoreduction using flame annealed TiO2 nanotubesPawan Kumar
The photocatalytic reduction of CO2 into light hydrocarbons using sunlight and water is a challenging reaction involving eight electron transfer steps; nevertheless, it has great potential to address the problem of rising anthropogenic carbon emissions and enable the use of fossil fuels in a sustainable way. Several decades after its first use, TiO2 remains one of the best performing and most durable photocatalysts for CO2 reduction albeit with a poor visible light absorption capacity. We have used flame annealing to improve the response of TiO2 to visible photons and engineered a nanotubular morphology with square-shaped cross-sections in flame-annealed nanotubes. An enhanced CH4 yield was achieved in the photoreduction of CO2 using flame annealed TiO2 nanotubes, and isotope labeled experiments confirmed the reaction products to originate from the CO2 reactant. Flame-annealed TiO2 nanotubes formed in aqueous electrolyte (FANT-aq) yielded 156.5 μmol gcatalyst–1.hr–1 of CH4, which is in the top tier of reported performance values achieved using TiO2 as a stand-alone photocatalyst. This performance resulted because appreciable amounts of CH4 were generated under visible light illumination as well. TiO2 nanotubes exhibited CO2 photoreduction activity up to a wavelength of 620 nm with visible light driven photocatalytic activity peaking at 450 nm for flame annealed TiO2 nanotubes. Isotope labelling studies, using GC–MS and gas-phase FTIR, indicated photoreduction of 13CO2 to 13CH4. The detection of 13CO in the product mixture, and the absence of HCHO and HCOOH provides strong support for the photoreduction proceeding along a carbene pathway. The enhanced CO2 photoreduction performance of FANT-aq is attributed to increased visible light absorption, square morphology, and the presence of rutile as the only crystalline phase with (110) as the dominant plane.
High rate CO2 photoreduction using flame annealed TiO2 nanotubesPawan Kumar
The photocatalytic reduction of CO2 into light hydrocarbons using sunlight and water is a challenging reaction involving eight electron transfer steps; nevertheless, it has great potential to address the problem of rising anthropogenic carbon emissions and enable the use of fossil fuels in a sustainable way. Several decades after its first use, TiO2 remains one of the best performing and most durable photocatalysts for CO2 reduction albeit with a poor visible light absorption capacity. We have used flame annealing to improve the response of TiO2 to visible photons and engineered a nanotubular morphology with square-shaped cross-sections in flame-annealed nanotubes. An enhanced CH4 yield was achieved in the photoreduction of CO2 using flame annealed TiO2 nanotubes, and isotope labeled experiments confirmed the reaction products to originate from the CO2 reactant. Flame-annealed TiO2 nanotubes
Optical Control of Selectivity of High Rate CO2 Photoreduction Via Interband-...Pawan Kumar
Photonic crystals consisting of TiO2 nanotube arrays (PMTiNTs) with periodically modulated diameters were fabricated using a precise charge-controlled pulsed anodization technique. The PMTiNTs were decorated with gold nanoparticles (Au NPs) to form plasmonic photonic crystal photocatalysts (Au-PMTiNTs). A systematic study of CO2 photoreduction performance on as-prepared samples was conducted using different wavelengths and illumination sequences. A remarkable selectivity of the mechanism of CO2 photoreduction could be engineered by merely varying the spectral composition of the illumination sequence. Under AM1.5 G simulated sunlight (pathway#1), the Au-PMTiNTs produced methane (302 µmol h-1) from CO2 with high selectivity (89.3%). When also illuminated by a UV-poor white lamp (pathway#2), the Au-PMTiNTs produced formaldehyde (420 µmol h-1) and carbon monoxide (323 µmol h-1) with almost no methane evolved. We confirmed the photoreduction results by 13C isotope labeling experiments using GC-MS. These results point to optical control of the selectivity of high-rate CO2 photoreduction through selection of one of two different mechanistic pathways. Pathway#1 implicates electron-hole pairs generated through interband transitions in TiO2 and Au as the primary active species responsible for reducing CO2 to methane. Pathway#2 involves excitation of both TiO2 and surface plasmons in Au. Hot electrons produced by plasmon damping and photogenerated holes in TiO2 proceed to reduce CO2 to HCHO and CO through a plasmonic Z-scheme.
Fabrication of zn o nanorod modified ITOViolet Flower
This document discusses the fabrication and characterization of zinc oxide (ZnO) nanorod arrays deposited on indium tin oxide (ITO) glass substrates via chemical bath deposition. Key points:
- ZnO nanorods were grown on ITO-coated glass by immersing the substrates in solutions containing zinc nitrate and hexamethylenetetramine at 80°C for varying times.
- Scanning electron microscopy images showed the diameter of the ZnO nanorods increased with higher solution concentration and longer growth time.
- X-ray diffraction analysis identified the crystal structure of the ZnO nanorods. Electrochemical measurements including cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electron transfer properties of
Vapor growth of binary and ternary phosphorusbased semiconductors into TiO2 n...Pawan Kumar
We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with
the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12)
were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing
vapor phase reaction deposition, the cavities of 100 mm long TiO2 nanotubes were infiltrated;
approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive
characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman
spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the
substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water
splitting performance compared to pristine materials and were found to be more active at higher
wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The
improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge
transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2.
IRJET-A Review on Utilization of Waste Heat from Automobile Based on Thermoel...IRJET Journal
This document discusses using metal-doped zinc oxide nanoparticles for water treatment in industries. It begins by introducing zinc oxide nanoparticles and the need to dope them with metals like magnesium to modify their properties. It then describes how magnesium-doped zinc oxide nanoparticles were synthesized using a sol-gel method. Characterization of the nanoparticles showed they were uniform in size and distribution. Experiments were conducted using these nanoparticles to degrade methylene blue dye in water via a photocatalytic process when exposed to light. The mechanism of photocatalysis is explained where light generates electron-hole pairs that initiate degradation reactions on the nanoparticle surfaces. The goal is to use this process to treat wastewater from industries in an efficient and environmentally friendly
This document describes the synthesis and characterization of a core-shell structured reduced graphene oxide wrapped magnetically separable rGO@CuZnO@Fe3O4 microspheres photocatalyst and its use for the photoreduction of carbon dioxide to methanol under visible light irradiation. The photocatalyst takes advantage of the high photocatalytic efficiency of zinc oxide, the high surface area and charge carrier mobility of reduced graphene oxide, and the magnetic properties of an iron oxide core. Experimental results showed the rGO@CuZnO@Fe3O4 photocatalyst had higher catalytic activity than other possible combinations, with a methanol yield of 2656 μmol/gcat under visible light, and could be readily recovered and
The present work demonstrates for the first time the facile fabrication of TiO2
nanotube arrays (TNTAs) by a fluoride-free
solid-state anodization process using LiClO4
containing solid polymeric electrolyte. The resulting nanotubes were tested
for photoelectrochemical water splitting. The elimination of liquid electrolytes in electrochemical anodization constitutes
a paradigm shift for the formation of nanoporous and nanotubular metal oxides. Our results open a new area of research
that uses the distinctive properties of solid polymer electrolytes to achieve targeted doping and nano-morphologies. Characterization
of the grown TNTAs indicated solid state anodized TNTAs to consist purely of the anatase phase of titania.
The solid-state anodization process provides several advantages over conventional liquid electrolytes such as easy handling
and processing, better charge transport, environmentally benign chemicals and methodology. Photoelectrochemical water
splitting experiments were performed which confirmed the viability of TNTAs grown by the new solid-state process for
photocatalytic applications.
This document discusses the use of titanium dioxide nanomaterials in photovoltaic applications. It begins by introducing the properties and polymorphs of titanium dioxide. The main sections then summarize the use of titanium dioxide nanomaterials in different types of solar cells, including dye-sensitized solar cells, polymer-inorganic hybrid solar cells, quantum dot-sensitized solar cells, inorganic solid-state solar cells, and perovskite solar cells. For each application, it provides a brief introduction to the solar cell type and discusses how nanostructured titanium dioxide materials can improve device performance through increased surface area and modulation of interfacial charge transfer kinetics.
We'd like to understand how you use our websites in order to improve them. Re...Pawan Kumar
The present work demonstrates for the first time the facile fabrication of TiO2 nanotube arrays (TNTAs) by a fluoride-free solid-state anodization process using LiClO4 containing solid polymeric electrolyte. The resulting nanotubes were tested for photoelectrochemical water splitting. The elimination of liquid electrolytes in electrochemical anodization constitutes a paradigm shift for the formation of nanoporous and nanotubular metal oxides. Our results open a new area of research that uses the distinctive properties of solid polymer electrolytes to achieve targeted doping and nano-morphologies. Characterization of the grown TNTAs indicated solid state anodized TNTAs to consist purely of the anatase phase of titania. The solid-state anodization process provides several advantages over conventional liquid electrolytes such as easy handling and processing, better charge transport, environmentally benign …
Similar to The effect of band engineering of semiconductors on (20)
Hudhud cyclone caused extensive damage in Visakhapatnam, India in October 2014, especially to tree cover. This will likely impact the local environment in several ways: increased air pollution as trees absorb less; higher temperatures without tree canopy; increased erosion and landslides. It also created large amounts of waste from destroyed trees. Proper management of solid waste is needed to prevent disease spread. Suggested measures include restoring damaged plants, building fountains to reduce heat, mandating light-colored buildings, improving waste management, and educating public on health risks. Overall, changes are needed to water, land, and waste practices to rebuild the environment after the cyclone removed green cover.
Impact of flood disaster in a drought prone area – case study of alampur vill...eSAT Publishing House
1) In September-October 2009, unprecedented heavy rainfall and dam releases caused widespread flooding in Alampur village in Mahabub Nagar district, a historically drought-prone area.
2) The flood damaged or destroyed homes, buildings, infrastructure, crops, and documents. It displaced many residents and cut off the village.
3) The socioeconomic conditions and mud-based construction of homes in the village exacerbated the flood's impacts, making damage more severe and recovery more difficult.
The document summarizes the Hudhud cyclone that struck Visakhapatnam, India in October 2014. It describes the cyclone's formation, rapid intensification to winds of 175 km/h, and landfall near Visakhapatnam. The cyclone caused extensive damage estimated at over $1 billion and at least 109 deaths in India and Nepal. Infrastructure like buildings, bridges, and power lines were destroyed. Crops and fishing boats were also damaged. The document then discusses coping strategies and improvements needed to disaster management plans to better prepare for future cyclones.
Groundwater investigation using geophysical methods a case study of pydibhim...eSAT Publishing House
This document summarizes the results of a geophysical investigation using vertical electrical sounding (VES) methods at 13 locations around an industrial area in India. The VES data was interpreted to generate geo-electric sections and pseudo-sections showing subsurface resistivity variations. Three main layers were typically identified - a high resistivity topsoil, a weathered middle layer, and a basement rock. Pseudo-sections revealed relatively more weathered areas in the northwest and southwest. Resistivity sections helped identify zones of possible high groundwater potential based on low resistivity anomalies sandwiched between more resistive layers. The study concluded the electrical resistivity method was useful for understanding subsurface geology and identifying areas prospective for groundwater exploration.
Flood related disasters concerned to urban flooding in bangalore, indiaeSAT Publishing House
1. The document discusses urban flooding in Bangalore, India. It describes how factors like heavy rainfall, population growth, and improper land use have contributed to increased flooding in the city.
2. Flooding events in 2013 are analyzed in detail. A November rainfall caused runoff six times higher than the drainage capacity, inundating low-lying residential areas.
3. Impacts of urban flooding include disrupted daily life, damaged infrastructure, and decreased economic activity in affected areas. The document calls for improved flood management strategies to better mitigate urban flooding risks in Bangalore.
Enhancing post disaster recovery by optimal infrastructure capacity buildingeSAT Publishing House
This document discusses enhancing post-disaster recovery through optimal infrastructure capacity building. It presents a model to minimize the cost of meeting demand using auxiliary capacities when disaster damages infrastructure. The model uses genetic algorithms to select optimal capacity combinations. The document reviews how infrastructure provides vital services supporting recovery activities and discusses classifying infrastructure into six types. When disaster reduces infrastructure services, a gap forms between community demands and available support, hindering recovery. The proposed research aims to identify this gap and optimize capacity selection to fill it cost-effectively.
Effect of lintel and lintel band on the global performance of reinforced conc...eSAT Publishing House
This document analyzes the effect of lintels and lintel bands on the seismic performance of reinforced concrete masonry infilled frames through non-linear static pushover analysis. Four frame models are considered: a frame with a full masonry infill wall; a frame with a central opening but no lintel/band; a frame with a lintel above the opening; and a frame with a lintel band above the opening. The results show that the full infill wall model has 27% higher stiffness and 32% higher strength than the model with just an opening. Models with lintels or lintel bands have slightly higher strength and stiffness than the model with just an opening. The document concludes lintels and lintel
Wind damage to trees in the gitam university campus at visakhapatnam by cyclo...eSAT Publishing House
1) A cyclone with wind speeds of 175-200 kph caused massive damage to the green cover of Gitam University campus in Visakhapatnam, India. Thousands of trees were uprooted or damaged.
2) A study assessed different types of damage to trees from the cyclone, including defoliation, salt spray damage, damage to stems/branches, and uprooting. Certain tree species were more vulnerable than others.
3) The results of the study can help in selecting more wind-resistant tree species for future planting and reducing damage from future storms.
Wind damage to buildings, infrastrucuture and landscape elements along the be...eSAT Publishing House
1) A visual study was conducted to assess wind damage from Cyclone Hudhud along the 27km Visakha-Bheemli Beach road in Visakhapatnam, India.
2) Residential and commercial buildings suffered extensive roof damage, while glass facades on hotels and restaurants were shattered. Infrastructure like electricity poles and bus shelters were destroyed.
3) Landscape elements faced damage, including collapsed trees that damaged pavements, and debris in parks. The cyclone wiped out over half the city's green cover and caused beach erosion around protected areas.
1) The document reviews factors that influence the shear strength of reinforced concrete deep beams, including compressive strength of concrete, percentage of tension reinforcement, vertical and horizontal web reinforcement, aggregate interlock, shear span-to-depth ratio, loading distribution, side cover, and beam depth.
2) It finds that compressive strength of concrete, tension reinforcement percentage, and web reinforcement all increase shear strength, while shear strength decreases as shear span-to-depth ratio increases.
3) The distribution and amount of vertical and horizontal web reinforcement also affects shear strength, but closely spaced stirrups do not necessarily enhance capacity or performance.
Role of voluntary teams of professional engineers in dissater management – ex...eSAT Publishing House
1) A team of 17 professional engineers from various disciplines called the "Griha Seva" team volunteered after the 2001 Gujarat earthquake to provide technical assistance.
2) The team conducted site visits, assessments, testing and recommended retrofitting strategies for damaged structures in Bhuj and Ahmedabad. They were able to fully assess and retrofit 20 buildings in Ahmedabad.
3) Factors observed that exacerbated the earthquake's impacts included unplanned construction, non-engineered buildings, improper prior retrofitting, and defective materials and workmanship. The professional engineers' technical expertise was crucial for effective post-disaster management.
This document discusses risk analysis and environmental hazard management. It begins by defining risk, hazard, and toxicity. It then outlines the steps involved in hazard identification, including HAZID, HAZOP, and HAZAN. The document presents a case study of a hypothetical gas collecting station, identifying potential accidents and hazards. It discusses quantitative and qualitative approaches to risk analysis, including calculating a fire and explosion index. The document concludes by discussing hazard management strategies like preventative measures, control measures, fire protection, relief operations, and the importance of training personnel on safety.
Review study on performance of seismically tested repaired shear wallseSAT Publishing House
This document summarizes research on the performance of reinforced concrete shear walls that have been repaired after damage. It begins with an introduction to shear walls and their failure modes. The literature review then discusses the behavior of original shear walls as well as different repair techniques tested by other researchers, including conventional repair with new concrete, jacketing with steel plates or concrete, and use of fiber reinforced polymers. The document focuses on evaluating the strength retention of shear walls after being repaired with various methods.
Monitoring and assessment of air quality with reference to dust particles (pm...eSAT Publishing House
This document summarizes a study on monitoring and assessing air quality with respect to dust particles (PM10 and PM2.5) in the urban environment of Visakhapatnam, India. Sampling was conducted in residential, commercial, and industrial areas from October 2013 to August 2014. The average PM2.5 and PM10 concentrations were within limits in residential areas but moderate to high in commercial and industrial areas. Exceedance factor levels indicated moderate pollution for residential areas and moderate to high pollution for commercial and industrial areas. There is a need for management measures like improved public transport and green spaces to combat particulate air pollution in the study areas.
Low cost wireless sensor networks and smartphone applications for disaster ma...eSAT Publishing House
This document describes a low-cost wireless sensor network and smartphone application system for disaster management. The system uses an Arduino-based wireless sensor network comprising nodes with various sensors to monitor the environment. The sensor data is transmitted to a central gateway and then to the cloud for analysis. A smartphone app connected to the cloud can detect disasters from the sensor data and send real-time alerts to users to help with early evacuation. The system aims to provide low-cost localized disaster detection and warnings to improve safety.
Coastal zones – seismic vulnerability an analysis from east coast of indiaeSAT Publishing House
This document summarizes an analysis of seismic vulnerability along the east coast of India. It discusses the geotectonic setting of the region as a passive continental margin and reports some moderate seismic activity from offshore in recent decades. While seismic stability cannot be assumed given events like the 2004 tsunami, no major earthquakes have been recorded along this coast historically. The document calls for further study of active faults, neotectonics, and implementation of improved seismic building codes to mitigate vulnerability.
Can fracture mechanics predict damage due disaster of structureseSAT Publishing House
This document discusses how fracture mechanics can be used to better predict damage and failure of structures. It notes that current design codes are based on small-scale laboratory tests and do not account for size effects, which can lead to more brittle failures in larger structures. The document outlines how fracture mechanics considers factors like size effect, ductility, and minimum reinforcement that influence the strength and failure behavior of structures. It provides examples of how fracture mechanics has been applied to problems like evaluating shear strength in deep beams and investigating a failure of an oil platform structure. The document argues that fracture mechanics provides a more scientific basis for structural design compared to existing empirical code provisions.
This document discusses the assessment of seismic susceptibility of reinforced concrete (RC) buildings. It begins with an introduction to earthquakes and the importance of vulnerability assessment in mitigating earthquake risks and losses. It then describes modeling the nonlinear behavior of RC building elements and performing pushover analysis to evaluate building performance. The document outlines modeling RC frames and developing moment-curvature relationships. It also summarizes the results of pushover analyses on sample 2D and 3D RC frames with and without shear walls. The conclusions emphasize that pushover analysis effectively assesses building properties but has limitations, and that capacity spectrum method provides appropriate results for evaluating building response and retrofitting impact.
A geophysical insight of earthquake occurred on 21 st may 2014 off paradip, b...eSAT Publishing House
1) A 6.0 magnitude earthquake occurred off the coast of Paradip, Odisha in the Bay of Bengal on May 21, 2014 at a depth of around 40 km.
2) Analysis of magnetic and bathymetric data from the area revealed the presence of major lineaments in NW-SE and NE-SW directions that may be responsible for seismic activity through stress release.
3) Movements along growth faults at the margins of large Bengal channels, due to large sediment loads, could also contribute to seismic events by triggering movements along the faults.
Effect of hudhud cyclone on the development of visakhapatnam as smart and gre...eSAT Publishing House
This document discusses the effects of Cyclone Hudhud on the development of Visakhapatnam as a smart and green city through a case study and preliminary surveys. The surveys found that 31% of participants had experienced cyclones, 9% floods, and 59% landslides previously in Visakhapatnam. Awareness of disaster alarming systems increased from 14% before the 2004 tsunami to 85% during Cyclone Hudhud, while awareness of disaster management systems increased from 50% before the tsunami to 94% during Hudhud. The surveys indicate that initiatives after the tsunami improved awareness and preparedness. Developing Visakhapatnam as a smart, green city should consider governance
A review on techniques and modelling methodologies used for checking electrom...nooriasukmaningtyas
The proper function of the integrated circuit (IC) in an inhibiting electromagnetic environment has always been a serious concern throughout the decades of revolution in the world of electronics, from disjunct devices to today’s integrated circuit technology, where billions of transistors are combined on a single chip. The automotive industry and smart vehicles in particular, are confronting design issues such as being prone to electromagnetic interference (EMI). Electronic control devices calculate incorrect outputs because of EMI and sensors give misleading values which can prove fatal in case of automotives. In this paper, the authors have non exhaustively tried to review research work concerned with the investigation of EMI in ICs and prediction of this EMI using various modelling methodologies and measurement setups.
Literature Review Basics and Understanding Reference Management.pptxDr Ramhari Poudyal
Three-day training on academic research focuses on analytical tools at United Technical College, supported by the University Grant Commission, Nepal. 24-26 May 2024
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
A SYSTEMATIC RISK ASSESSMENT APPROACH FOR SECURING THE SMART IRRIGATION SYSTEMSIJNSA Journal
The smart irrigation system represents an innovative approach to optimize water usage in agricultural and landscaping practices. The integration of cutting-edge technologies, including sensors, actuators, and data analysis, empowers this system to provide accurate monitoring and control of irrigation processes by leveraging real-time environmental conditions. The main objective of a smart irrigation system is to optimize water efficiency, minimize expenses, and foster the adoption of sustainable water management methods. This paper conducts a systematic risk assessment by exploring the key components/assets and their functionalities in the smart irrigation system. The crucial role of sensors in gathering data on soil moisture, weather patterns, and plant well-being is emphasized in this system. These sensors enable intelligent decision-making in irrigation scheduling and water distribution, leading to enhanced water efficiency and sustainable water management practices. Actuators enable automated control of irrigation devices, ensuring precise and targeted water delivery to plants. Additionally, the paper addresses the potential threat and vulnerabilities associated with smart irrigation systems. It discusses limitations of the system, such as power constraints and computational capabilities, and calculates the potential security risks. The paper suggests possible risk treatment methods for effective secure system operation. In conclusion, the paper emphasizes the significant benefits of implementing smart irrigation systems, including improved water conservation, increased crop yield, and reduced environmental impact. Additionally, based on the security analysis conducted, the paper recommends the implementation of countermeasures and security approaches to address vulnerabilities and ensure the integrity and reliability of the system. By incorporating these measures, smart irrigation technology can revolutionize water management practices in agriculture, promoting sustainability, resource efficiency, and safeguarding against potential security threats.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
Introduction- e - waste – definition - sources of e-waste– hazardous substances in e-waste - effects of e-waste on environment and human health- need for e-waste management– e-waste handling rules - waste minimization techniques for managing e-waste – recycling of e-waste - disposal treatment methods of e- waste – mechanism of extraction of precious metal from leaching solution-global Scenario of E-waste – E-waste in India- case studies.
Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
This paper describes a speed control device for generating electrical energy on an electricity network based on the doubly fed induction generator (DFIG) used for wind power conversion systems. At first, a double-fed induction generator model was constructed. A control law is formulated to govern the flow of energy between the stator of a DFIG and the energy network using three types of controllers: proportional integral (PI), sliding mode controller (SMC) and second order sliding mode controller (SOSMC). Their different results in terms of power reference tracking, reaction to unexpected speed fluctuations, sensitivity to perturbations, and resilience against machine parameter alterations are compared. MATLAB/Simulink was used to conduct the simulations for the preceding study. Multiple simulations have shown very satisfying results, and the investigations demonstrate the efficacy and power-enhancing capabilities of the suggested control system.
The effect of band engineering of semiconductors on
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THE EFFECT OF BAND ENGINEERING OF SEMICONDUCTORS ON
PHOTOCATALYIC WATER SPLITTING: A REVIEW
Lee Chung Lau1
, KeatTeong Lee2
1, 2
School of Chemical Engineering, UniversitiSains Malaysia, Engineering Campus, Seri Ampangan, 14300 NibongTebal,
Pulau Pinang, Malaysia, chktlee@eng.usm.my
Abstract
The direct conversion of solar energy using a photocatalyst in a water splitting reaction is a source of a sustainable and clean
hydrogen supply. In general, photocatalysts are semiconductors that possess valence and conduction bands. These energy bands
permit the absorption of photon energy to excite electrons in the outer orbitals of the photocatalysts. Photoexcited electron and hole
pairs can subsequently induce a watersplitting reaction to produce hydrogen and oxygen. Photocatalytic water splitting is affected by
the band level and crystallinity of the photocatalyst. Therefore, band engineering using chemical modifications such as cationic and
anionic modification could createa photocatalyst suitable for the large-scale production of hydrogen. In this paper, cationic and
anionic modifications of photocatalysts and the effects of these modifications onphotocatalytic water splitting are reviewed.
Keywords: Water splitting; Photocatalysis; Hydrogen
----------------------------------------------------------------------***------------------------------------------------------------------------
1. INTRODUCTION
The growth of energy consumption worldwide has resulted in
an intensified use of fossil fuels. The resulting pollutants
produced during fossil fuel combustion and the depletion of
fossil fuels has encouraged a search for alternative and
renewable energy sources that will enhance both energy
security and environmental protection. The direct conversion
of solar energy into usable energy has been a promising
solution to the problem. Among various solar energy
technologies, photocatalytic water splitting has been studied
rigorously, especially after the discovery of Honda and
Fujishimain 1972[1].The photocatalytic water splitting
reaction evolves hydrogen, which is a form of clean energy
that produces no pollutants during combustion. In conjunction
with the development of fuel cell technology, transformation
into a hydrogen-based economy could be realized in the near
term, if an inexpensive and carbon-neutral source of hydrogen
is developed. A photocatalyst that could induce photocatalytic
water splitting has properties similar to a semiconductor. A
photocatalyst can a form conduction band and valence band
when the electrons located in the outer orbitals are excited by
photons from light irradiation. These excited electrons will
move into the conduction band while the valence band will
contain holes where the electrons were originally located.
These electron-hole pairs can subsequently react with
surrounding substrates, such as with a water molecule in a
redox reaction. A photo excited electron will reduce a water
molecule into hydrogen whereas a hole will oxidize the water
molecule to produce oxygen. In reality, not all electron-hole
pairs can induce water splitting because of electron-hole
recombination. Hydrogen or oxygen evolution is
thermodynamically possible only if the potential of the
conduction band is more negative than 0 V at NHE and if that
of the valence band is more positive than 1.23V at NHE, as
illustrated in Fig. 1. For an overall water splitting reaction,
(i.e., hydrogen and oxygen evolve at a stoichiometric ratio),the
band gap of the photocatalyst must be at least 1.23V, which
corresponds to light irradiation of 1100nm and indicates the
possibility of using visible and UV light irradiation to induce
photocatalytic water splitting. Most photocatalysts possess a
large band gap and are therefore only responsive to UV
irradiation. Solar irradiation consists of only 4-5% energy in
the UV region but 45% in the visible region. Thus, while the
idea of developing a visible light sensitive photocatalyst to
perform water splitting is reasonable, a photocatalyst with a
band structure that can absorb visible light irradiation and
thermodynamically induce an overall water splitting reaction
is not yet readily available. Therefore, band structure
engineering has been applied to narrow the band gap of
photocatalysts to construct a band structure that could induce
the water splitting reaction.
Fig.1.Energy structure of an effective photocatalyst
for the overall water splitting reaction
Energy Level
0V
1.23V
Conduction Band
Valence Band
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Band engineering of semiconductors has been performed by
adding a cocatalyst and dopants using various synthesis route.
In general, band engineering distorts the crystal structure and
modifies the band level of photocatalysts. A dopant that was
initially a center of recombination for electron-hole pairs can
act as an active site for water splitting reaction with
appropriate modification. Currently, cationic and anionic
modifications are the most popular methods to produce
photocatalysts for overall water splitting purposes. Cationic
additives are predominantly transition and noble metal ions
with d0
or d10
electronic configurations, while an ionic
additives typically consist of nitrogen, sulfur and chlorine
compounds. The combination of both modification types is
also applicable to improve photocatalytic performance. This
paper discusses cationic and anionic modifications of
photocatalysts and their effects on band structure and
photocatalytic water splitting.
2. CATIONICMODIFICATION
Transition metals are predominantly used to modify the band
structure of a semiconductor. Examples of cationic additives
include Bi, Mo, Au, Rh, Zr, Pt, Ru, Cr, Ni, V, Fe, La, In and
Ce. TiO2is the most popular photocatalyst and has been widely
modified by various cautions. A cocatalyst and dopants are
incorporated into TiO2 rutile and anatase phase to narrow the
TiO2 band gap, extending the absorption edge from the UV to
visible light region. The Bi-dopedTiO2studied by Naik et al. is
one example of a d10
cationic dopants for TiO2[2]. This nano
composite was synthesized using a soft chemical template free
homogeneous co-precipitation method. A mesoporous
compound formed with a significant red shift in the absorption
edge was formed, indicating its capability of absorbing more
lights with a longer wavelength. After calcination at 400°C,
4.3% of the apparent quantum efficiency was achieved at198.4
μmol/h of H2. TiO2 films doped with Mo were prepared by Li
et al. using the layer-by-layer method [3]. Optimum Mo
doping enhanced the transformation from the anatase to the
rutile phase and reduced the surface oxygen vacancies that
could promote recombination of the photo induced charges.
The doped TiO2 exhibited photocatalytic activity 3.3 times
higher than the bare TiO2 because the introduction of Mo6+
resulted in a red shift of the absorption edge to the visible
region.
In addition, the function of Au as a cocatalyst has been
investigated by many researchers. Lin et al. deposited gold
nanoparticles on KTiNbO5 using the deposition precipitation
method [4]. Due to effective photo excited charge separation,
the photo activity of 0.63wt% Au/KTiNbO5 with uniformly
dispersed gold nanoparticles was 47 times higher than that of
bare KTiNbO5. Lunawat et al. studied a Au-doped CdS/SBA-
15 photocatalyst[5]. In their study, Pt and Au dopants
produced entirely different activity in CdS/SBA-15. The Au-
doped CdS/SBA-15 exhibited decreased photo activity, while
the Pt-doped CdS/SBA-15 exhibited a substantial increase
compared with the undoped CdS/SBA-15. The researchers
explained that the surface properties, rather than the electronic
structure, of their photocatalysts played an important role.
Anoptimum crystallite size is crucial in avoiding active site
blockage by metal particles. Feil et al. used a modified
classical citrate method in synthesizing a gold impregnated
TiO2photocatalyst[6]. In their study, anodic oxidation of Ti
metal in fluoride electrolytes containing gold nanoparticles
was used to grow TiO2 nano tube arrays. Using methanol as a
sacrificial reagent, the Au doped TiO2 nanotubes exhibited
higher photocatalytic hydrogen production than the Au-free
TiO2 nanotubes. Chiarello et al. prepared Au/TiO2 sample
using flame spray pyrolysis [7]. At 1% Au doping, an
additional absorption band was observed in the visible region.
The absorption band was named the plasmonic absorption
band and led to the purple color of the prepared photocatalyst.
The resulting hydrogen evolution rate from photocatalytic
water splitting was observed to be one order of magnitude
higher than that of the undoped TiO2. Rosseler et al.
synthesized a Au/TiO2photocatalystusing the sol-gel and
subsequent direct anionic exchange process with various types
of TiO2 and porogens[8]. Their study revealed that
photocatalytic water splitting is affected by the type of
metallic doping, surface properties, anatase/rutile ratio, metal-
support interaction and amount of methanol. In fact, high H2
production efficiency (120μmol/min) was achieved over days
without deactivation and with a low amount of methanol.
Chen et al. prepared Au/TiO2 via the sodium citrate reduction
method to study the effect of surface plasmon resonance (SPR)
on photocatalytic water splitting using simulated solar
irradiation [9]. The effect of the Au addition on TiO2 is
illustrated in Fig.2. The Au particles act as electron traps and
active sites to improve the hydrogen evolution activity. In
addition, the intensified electric field at the interface between
the Au particle and TiO2 contributes to enhanced water
splitting activity when both UV and visible light irradiation
were used. Nevertheless, no H2 evolution was observed when
Au/TiO2 in pure water was irradiated with only visible light,
which implies that the SPR effect from the gold particles is
insufficient to produce the water splitting reaction. Comparing
discussed research works, Au/TiO2 possess greater hydrogen
evolution rate if sacrificial reagents like methanol was used.
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Fig. 2.Plasmonic absorption band derived from gold
modification [9].
The d6
electronic structure of rhodium (Rh) has also been
studied intensively [10-17]. Detailed studies have
demonstrated that (Ga1-xZnx)(N1-xOx) is a promising visible
light active photocatalyst[10, 14-17]. When doping (Ga1-
xZnx)(N1-xOx) with Rh, its photocatalytic activity was observed
to increase. Nevertheless, because hydrogen and oxygen
recombination occurred as they were catalyzed by Rh, Maeda
et al. coated rhodium particled with chromium oxide,Rh-
Cr2O3via photo deposition from aqueous metal precursors. The
impregnation of chromium oxide successfully suppressed the
recombination of hydrogen and oxygen. The resulting
photocatalyst was able to produce hydrogen upon visible light
irradiation. In addition to the work of Maeda et al., Rh doping
has also been studied by Ma et al. [13] and Kumagai et al. [12].
Ma et al. studied potassium niobate nano scrolls doped with
Rh nanoparticles [13]. These researchers used rhodium
hydroxide as a precursor and prepared potassium niobate nano
scrolls using solid calcinations. Their results indicated that
0.1wt% Rh yielded optimum water splitting activity with
1340μmol/h per gram of photocatalyst. In addition, proton-
exchange using 1M HCl and subsequent hydration has also
been performed for the Rh doped photocatalyst. This
procedure enhances the hydrogen evolution rate to
1480μmol/h per gram of photocatalyst. Kumagai et al.
prepared Rh3+
doped ZnGa2O4 using a hydrothermal method
[12]. All the metal precursors were firstly mixed in a nitric
acid solution, and the resulting mixture was then combined
with ammonia to reach pH 9. After stirring for two hours, the
mixture was autoclaved at 80°C for 24 hours. After
centrifugation and filtration, the resulting yellowish
precipitates were washed with distilled water several times.
Upon drying, Rh2O3was added using RhCl3.3H2O as the
precursor via the impregnation method. Finally, calcination at
500°C for 1 hour was performed to obtain the photocatalyst.
Rh doping shifted the absorption edge of ZnGa2O4 into the
visible light region. H2 evolution in the presence of a
sacrificial reagent under visible light irradiation (>500nm)
confirmed the function of Rh2O3 as the active site for H2
evolution.
The use of ZrO2 doping to enhance the photocatalytic activity
of TaON has also been investigated [18-21]. TaOH has a
suitable band potential and is stable under photo corrosion to
act as a promising visible light driven photocatalyst. In these
studies, TaON was prepared via nitridation of Ta2O5 under a
NH3 flow at 1123K for 15 hours. Nevertheless, a high density
of surface defects on TaON resulted in low activity of the
photocatalyst. The surface defects acted as recombination
centers for the photo generated electron-hole pairs. By
incorporating ZrO2into the nitridation of Ta2O5, a highly
crystalline ZrO2-TaON resulted and surface defect formation
was suppressed. In addition, ZrO2suppressesthe aggregation of
particulate during nitridation, and aggregation causes a
reduction in photocatalytic activity. Under the reducing
atmosphere of NH3, reduced tantalum species formation (Ta3+
)
can be restrained by ZrO2, thereby causing it to become more
cationic, and increasing the visible light absorption of the
photocatalyst.
Pt has been applied to many types of catalytic reactions and
appears to be a noble metal dopant that always enhances
photocatalytic activity. Lin et al. employed the evaporation
induced self assembly (EISA) method to prepare mesoporous
Nb2O5[22]. Pt was then photo deposited as a cocatalyst into
the framework of Nb2O5.The Pt/Nb2O5was reported to produce
a high hydrogen evolution rate of 4647μmol/g.h in UV light
irradiated water splitting with methanol as the sacrificial
reagent; this rate is much higher than that other metal doped
Nb2O5. Well-dispersed Pt nanoparticles contributed to the
efficient charge separation in the photocatalyst. Pt doping on
TiO2wasalso intensively studied [23-27].Ikuma et al. produced
Pt on TiO2 via hydrogen reduction, photocatalytic and
formaldehyde reduction methods to decompose the precursor
H2PtCl6into Pt particles[24]. Different levels of photocatalytic
water splitting activity were observed for different deposition
methods. The formaldehyde reduction method where a TiO2
powder and H2PtCl6 mixture was placed in a formaldehyde
atmosphere at 400°C, was observed to yield the highest H2
evolution rate. Pt particles were not detected by Transmission
Electron Microscopy (TEM) for the formaldehyde reduced
Plasmonic absorption band
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Pt/TiO2, indicating that a fine or thin layer of Pt particles was
deposited. The Pt particles could be detected if heated at
800°C because agglomeration occurs. A Ce3+
/Ce4+
shuttle
charge UV-irradiated photocatalytic water splitting system
using Pt/TiO2was studied by Kozlova et al.[26]. A
Pt/TiO2photocatalystwas prepared using a soft chemical
method with sodium borohydride reducing H2PtCl6. In a
shuttle charge system, the hydrogen and oxygen evolution
reactions occur at different photocatalyst particles, implying
that hydrogen evolution and Ce3+
oxidation occur at same
particle and oxygen evolution and Ce4+
reduction occur at
another particle. This process reduces hydrogen and oxygen
recombination and is capable of producing hydrogen of high
purity, if the half reactions are performed separately in batches.
Photocatalytic water splitting from visible light irradiation
using Pt/TiO2was also studied using TiO2 nanotube[23]and
thin films[25].Pt was incorporated into the TiO2 nanotube
matrix using an ion exchange method, and the highly
dispersed Pt particles reduced the band gap of a bare TiO2
nanotube from 3.1 to 2.48 eV. If the Pt was aggregately
impregnated, the band gap reduction was not observed. The
Pt/TiO2 nanotube was visible light active and yielded
hydrogen evolution rates of 2.3 and 14.6 μmol/h using pure
water and methanol as sacrificial reagents, respectively. The
Pt/TiO2 thin film was however, prepared using the radio-
frequency magnetron sputtering deposition (RF-MS) method
and its absorption band was shifted into the visible range.
Pt/TiO2 thin films are applicable for photocatalytic water
splitting with sacrificial reagent such as methanol and AgNO3
solution using visible light with wavelengths longer than
550nm.
RuO2 doped photocatalysts have been studied by Inoue et
al.[28-34]. In their report, RuO2and divalent ion (Zn2+
, Mg2+
)
doped GaN were observed to be highly reactive and stable
photocatalyst for overall water splitting under UV
irradiation[28]. These photocatalysts were prepared by
nitridation of sulfide precursors and impregnation of the
resulting compounds with a Ru precursor, followed by
calcinations. The undoped GaN produced little hydrogen with
no oxygen; however, the doped GaN increased the hydrogen
and oxygen evolution in a stoichiometric ratio. This study also
revealed that RuO2 with tetravalent ion (Si4+
, Ge4+
) doped
GaN is not active for photocatalytic water splitting because
tetravalent ions distort the crystal structure differently than
divalent ions. The use of RuO2 doped β-Ge3N4 for overall
water splitting has also been demonstrated[3]. In this study,
sulfuric acid was observed to enhance the photocatalytic
activity because the basic condition tends to hydrolyze the
photocatalyst. Hydrolysis of the photocatalyst was observed to
collapse the catalyst surface and loosen the interfacial contact
between β-Ge3N4and RuO2, thus reducing the rate of H2 and
O2 evolution as the reaction progressed. This study also
demonstrated that regeneration of the photocatalyst can be
achieved through calcinations and RuO2 reloading to obtain 80%
of the initial activity. Subsequent studies of Inoue et al. have
also been reported [31-32]. From Kadowaki et al. [31],
inactive CeO2 with an f0
d0
electronic configuration has been
successful activated by doping RuO2 with Sr2+
. The formation
of Ce3+
, which was the main reason for CeO2 inactivity, was
suppressed by the dopants by promotion of the formation of
Ce4+
. This study is the first example of lanthanide metal
oxides as photocatalysts for an overall water splitting reaction.
Another photocatalyst, RuO2-PbWO4 was studied by
Kadowaki et al. [32]. PbWO4 was prepared via a solid state
reaction from oxide precursors and subsequently impregnated
with a Ru precursor, followed by calcinations. This
photocatalyst with a combination d10
s2
(Pb2+
)–d0
(W)
electronic configuration was more active towards UV
irradiation compared with inactive WO3. The enhancement of
the orbital dispersion by Pb2+
was determined to be a crucial
reason for the photo activity of this photocatalyst. A review of
RuO2 doped metal oxides and nitrides with d0
and d10
electronic configuration by Inoue et al. [30] has further
clarified the role of dopants in Photocatalysis. It was
concluded that distortion and unsymmetrical metal-oxygen
octahedral/tetrahedral coordination increase the photocatalytic
activity of d0
and d10
metal oxides. Further enhancement of
photocatalytic activity can be achieved if divalent metal ions
are incorporated in the electronic structure of the photocatalyst.
This phenomenon occurs because divalent metal ions will
contribute to a largely dispersed band and enhance the
mobility of the photo excited electrons. In addition to the work
by Inoue et al., the use of Ru as a cocatalyst has been reported
by Navarro et al. [35]. A CdS–CdO–ZnO photocatalyst was
prepared from sequential precipitation and Ru particles were
photo deposited under visible light irradiation. The addition of
Ru significantly increased the photo activity of CdS–CdO–
ZnO. The interaction between RuO2 and CdS reduces
electron-hole recombination and subsequently enhances water
splitting activity.
Maeda et al. have studied photocatalytic water splitting from
solid solution (Ga1-xZnx)(N1-xOx) using Rh/Cr2O3core/shell
nanoparticles as cocatalyst[14-15, 17, 36].Rh doped on (Ga1-
xZnx)(N1-xOx)did not promote photocatalytic water splitting
because of the recombination of hydrogen and oxygen on the
Rh particles. Coating Rh with Cr2O3suppressed the H2/O2
recombination, subsequently enhancing the overall water
splitting activity Rh and Cr2O3werephotodeposited in
sequence on (Ga1-xZnx)(N1-xOx) solid solutions using
Na3RhCl6.2H2O and K2CrO4 as precursors. This study also
revealed that the core/shell structure of Rh/Cr has higher water
splitting activity than Rh-Cr mixed oxides used as cocatalyst.
Maeda et al. suggested that the core/shell structure yields more
efficient electron transfer from the conduction band of (Ga1-
xZnx)(N1-xOx) to the Rh particle. This photocatalyst was
observed to be stable at pH 4.5. A reactant pH study indicated
that this photocatalyst would be corroded and hydrolyzed at
pH 3.0 and 6.2. IN addition to Maeda et al., the use of Cr in
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photocatalyst preparation has also been demonstrated [37-39].
Liu et al. [39] prepared Cr/SrTiO3 using a solvothermal
method. Compared with bare SrTiO3, Cr/SrTiO3 has greater
UV irradiated photocatalytic activity. Cr/SrTiO3was also
observed to be visible light responsive, which was attributed
to the band transition from the Cr 3d to the Cr 3d+Ti 3d hybrid
orbital. In addition, Cr-doping is also the main reason for the
visible light sensitive Cr-doped Bi4Ti3O12prepared via the sol-
gel route, as described in the work of Zhang et al. [38].
Cr2O3has also been used in the work of Zhang et al. to dope
TiO2 nanotubes[37]. The absorption spectrum is observed to
extend into the visible light region, making the photocatalyst
visible light active. Cr3+
predominantly contributed to visible
light water splitting activity by forming another valence band
to reduce the band gap from 3.3 (TiO2 nanotube) to 2.3 eV
(Cr2O3/TiO2 nanotube).
Nickel oxide is extensively doped with a perovskite type oxide
to improve its photocatalytic water splitting activity by visible
light irradiation. Jeong et al. synthesized NiO/Sr3Ti2O7 from a
solid state reaction method (SSRM) and a polymerized
complex method (PCM) [40]. Impregnation of NiO has
increased the photocatalytic activity of Sr3Ti2O7 significantly.
By comparison, PCM appears to be a better method to produce
NiO/Sr3Ti2O7because of the resulting higher photo activity
and stability towards prolonged irradiation. Visible light
irradiation using NiO/K4Nb6O17prepared by Lin et al.via a two
step solid state reaction was observed to exhibit higher
photocatalytic water splitting compared with the unloaded
K4Nb6O17 catalyst and the NiO/K4Nb6O17 prepared using a
conventional impregnation method [41]. The researchers
reported that NiO is well dispersed in the bulk structure
ofK4Nb6O17instead of the surface. Therefore, the shadowing
effect caused by NiO is minimized, allowing more light
absorption by the K4Nb6O17. In addition, photo generated
electron transfer to NiO becomes more efficient. NiO was also
doped into InTaO4 by Chiou et al. [42]. In their study,
InTaO4was prepared from a sol-gel method, instead of through
a conventional solid state reaction method, such that a thin
film of InTaO4was formed. InTaO4 is a visible light sensitive
material capable of splitting water under irradiation.
Impregnating NiO increases the initial hydrogen evolution rate
of InTaO4 because Ni/NiO core/shell nanoparticles efficiently
increase charge transfer and enhance the reduction of H+
to
hydrogen. Deactivation of NiO/InTaO4can occur when
Ni(OH)2 is formed. A similar indium photocatalyst, InVO4
doped with NiO, was also synthesized by Lin et al. [43].
Highly crystallized InVO4was active in producing H2from
visible light irradiation Subsequent impregnation with NiO
followed by reduction in H2 and oxidation in O2produced
NiO/InVO4with an ultra thin NiO layer and a metallic Ni core.
Distribution of the photo generated electrons by the ultra thin
structure contributed to a 40% increase in the photocatalytic
activity. NiO impregnation via a reduction-oxidation process
was also performed by Tang et al. to synthesize
NiOx/Sm2InTaO7[44]. This pyrochlore-type photocatalyst
could produce H2 from pure water under visible light
irradiation. NiO loading distorted the lattice and formed a
highly dispersed conduction band from a hybridized In 5s5p
orbital. Band structure changes caused by the NiO loading
were determined to be responsible for the high water splitting
activity. Anon noble metal photocatalyst doped with NiO was
presented by Wang et al. [45].NiO/Ca2Fe2O5synthesized via
the sol-gel and impregnation method was observed to be
active in producing hydrogen from pure water, even though
Ca2Fe2O5 is not an active photocatalyst. By adding CO2 and
NaHCO3 in the water splitting reaction, the hydrogen
evolution rate further increased because hole scavenging was
promoted and reduced charge recombination.
V doped K2La2Ti3O10was synthesized by Yang et al. via the
sol gel method [46]. At an optimum V doping of 1.5%,
increased photocatalytic hydrogen production was achieved
under both UV and visible light radiation. Vanadium doping
was observed to change the lattice parameter of K2La2Ti3O10,
but the crystal structure remained unchanged. In addition,
DRS demonstrated that visible light absorptive properties are
improved and favorable for photocatalytic activity.
Hybridization of the V3d electron orbit with the O2p electron
orbit forms a new localized energy level that allow the
photocatalyst to be excited at lower energy.
The performance of iron-doped Pt-TiO2 nanotubes prepared
via the sol gel method was analyzed by Eder et al. [47].
Improved photocatalytic activity by up to two orders of
magnitude was observed for the prepared photocatalyst when
compared with commercial TiO2.The authors claimed that the
absorption edge of the photocatalyst shifted considerably into
the visible light region and that this red shift resulted from the
excitation of Fe3+
3d electrons into the conduction band of
TiO2.Sasaki et al. loaded Fe2O3 onto SrTiO3:Rh in a Z-scheme
Photocatalysis system via the impregnation method [48].
However, in their work, the Fe2O3 doped photocatalyst did not
gain significant attention because the Ru doped photocatalyst
exhibited superior activity.
Li et al. synthesized La-doped Bi2AlNbO7via a solid state
reaction [49]. Their study revealed that lanthanum doping
increased the band gap of Bi2AlNbO7. The conduction band
defined by La 5d, Bi 6p and Nb 4d is observed to be more
positive than that of undoped Bi2AlNbO7. The water splitting
activity of Bi1.8La0.2AlNbO7was observed to be two times
higher, which was attributed to the change in the band
structure and La3+ on the photocatalyst surface. However, Yan
et al. studied the photocatalytic water splitting activity of La-
doped NaTaO3 prepared via microwave heating [50]. At 2%
doping, La0.02Na0.98TaO3 with good crystallinity and a high
surface area was formed and possessed improved
photocatalytic water splitting activity.
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Hu et al. demonstrated In3+
incorporation into GaON via a
hydrothermal and nitridation reaction [51]. GaON is visible
light sensitive photocatalyst; however the introduction of
In3+
further dispersed the hybridized orbitals, causing a red
shift of the DRS absorption edge, in which the photocatalytic
activity is improved. Wei et al. studied the photocatalytic
activity of In-doped H2LaNb2O7 prepared via a solid state
reaction [52]. Their study indicated that an optimum amount
of In doping exists such that the thickness of the space charge
layer is equal to the light penetration depth. This photocatalyst
was sensitive to visible light and capable of producing
hydrogen with sacrificial reagent.
Cerium doped zeolites were studied by Krishna et al. [53].
Zeolites alone are not active photocatalyst. By doping them
with low amount of cerium, the interaction between Ce3+
and
the support is responsive to irradiation to generate
photoelectrons and water molecules could be split to produce
hydrogen.
3. ANIONIC MODIFICATION
In general, oxide photocatalysts possess a large band gap that
is unresponsive to visible light irradiation. (Oxy)nitride
photocatalysts, however, have a narrower band gap and are
responsive to visible light irradiation. The valence band of an
(oxy)nitride photocatalyst consists of a N2p orbital that has a
lower potential than the valence band of the oxide
photocatalyst that is normally formed by the O2p orbital [54].
An (oxy) nitride photocatalyst, therefore has a broader
absorption band in the visible region. Nevertheless, compared
with an oxide photocatalyst, an (oxy)nitride photocatalyst is
typically not thermally stable and undergoes photo corrosion.
Several types of (oxy)nitride photocatalyst that have been
under extensive research recently include GaN, GeN,
perovskiteoxynitride, N-TiO2 and TaON, and these are
discussed in the following section.
Arai et al. demonstrated the preparation of GaN from Ga2S2
using nitridation in a NH3 flow at 1273K for 15 hours [55].
The GaN formed was only active in the UV region. However,
doping divalent ions such as Zn2+
, Mg2+
and
Be2+
couldtransformGaNinto a visible light responsive material
with high photocatalytic water splitting activity, and further
enhancement could be achieved if RuO2was present as a co-
catalyst. Doping with a divalent ion was observed to increase
the concentration and mobility of the holes. An N-doped GaO
and ZnO solid solution was also studied by Parida et al.[56].
Prepared from a solid state reaction, the GaO-ZnO was added
to different nitrogen precursors such as urea, glycine,
hexamine and pyridine. N-doping reduced the band gap from
4.1 to 2.6 eV and extended the absorption band further into the
visible light region. An apparent quantum efficiency of 5.1%
by visible light irradiation was achieved using glycine as the
N-precursor. Kamata et al. added Into the oxynitride
photocatalyst to form Ga-Zn-In oxynitride[57]. The absorption
edge of the photocatalyst reached 600 nm and the water
molecules were photo catalytically split with suitable electron
donors and acceptors. Although the photocatalyst was
observed to be unstable in water oxidation reaction,
modification with cobalt oxide stabilizes the system as an
oxygen evolution promoter
Similarly to GaN, Ge has also used in the formation of (oxy)
nitride photo catalyst. The synthesis of a photocatalyst from a
solid solution of ZnO and GeN was performed by Takanabe et
al., Wang et al. and Lee et al.[58-60]. They shared similar
findings indicating that the absorption band in the visible light
region was attributed to the valence band that consisted of
hybridized Zn3d and N2p orbitals. The overall water splitting
activity could be enhanced by doping metal ions such as Cu
and Rh-Cr2O3. The enhancement in activity was largely
contributed to the high crystallinity because metal doping
suppresses defect formation. A low defect concentration,
which is also achievable through post calcinations after the
nitridation process, is important in reducing the charge
recombination. Nitridation of perovskite type materials has
also been performed to synthesize visible light responsive
photocatalysts. Hagiwara et al. synthesize N-doped
Pt/KTa0.92Zr0.08O3via NH3nitridation[61]. The visible light
inactive Pt/KTa0.92Zr0.08O3wasobserved to split water
molecules under visible light irradiation after nitrogen doping
The absorption edge of the photocatalyst extended from 350 to
600 nm upon nitrogen doping, which was attributed to the
formation of Ta3N5. Perovskite niobium (oxy)nitrides were
produced by Siritanaratkul et al. [62]. The photocatalytic
water splitting of different types of perovskite type niobium
oxynitrides such as CaNbO2N, SrNbO2N, BaNbO2N and
LaNbON2were examined. Prepared via a polymerized
complex method and ammonia nitridation, these
photocatalysts exhibited a wide absorption band at high
wavelengths (600-750 nm). The nitridation temperature
appeared to be the dominant factor in producing
photocatalysts with high water splitting activity. At lower
temperature, the oxynitride phase was not properly formed,
whereas at high temperature, reduced niobium species (Nb3+
,
Nb4+
) that can act as charge recombination sites formed and
caused lower activity.
TiO2 is only sensitive to UV irradiation. However, several
studies have demonstrated that through nitrogen doping, the
absorption band of N-TiO2 is extended deep into the visible
light region. Yuan et al. prepared N-TiO2 using urea as the
nitrogen precursor [63].They observed that the absorption
edge was shifted up to 600 nm in the visible light region.
Through XPS analysis, nitrogen was observed to present as
chemisorbed N2 and substituted N. The substituted N was
responsible for the visible light photocatalytic water splitting.
Transformation from the anatase to the rutile phase was also
observed to contribute to the activity. Sreethawong et al.
studied the effect of the mesoporous structure of N-TiO2on the
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visible light water splitting activity [64]. These researchers
determined that the photocatalyst prepared from mesoporous
TiO2had higher activity compared with non-mesoporous TiO2.
Subsequently, Pt/N-TiO2was prepared to obtain higher
photocatalytic activity[27]. Platinum doping remarkably
increased the photo activity with an optimum loading of 1.3
wt%. In this photocatalytic system, good dispersion of
platinum particles was significant to enhancing the water
splitting activity. A d0
-d10
complex photocatalyst, ZnxTiOyNz
was synthesized by Hisatomi et al. via the polymerized
complex method [65]. The absorption band edge of this
spinel-type oxynitride photo catalyst was extended to 550 nm,
and water splitting occurred under visible light irradiation in a
sacrificial reagent such as methanol and silver nitrate.
TaON has been studied considerably as a visible light
photocatalyst. TaON can be produced from the nitridation of
Ta2O5. However, due to its band position, TaON is only
capable of producing hydrogen instead of the overall water
splitting reaction, with low hydrogen evolution activity.
Defects in the bulk and on the surface of TaON(reduced
tantalum species) can act as electron-hole recombination
centers that decrease photo activity. Post calcinations after
nitridation is one approach to reduce the defects, but this
approach is less appropriate because TaON is not thermally
stable. Maeda et al. added ZrO2 to reduce the defects in the
TaON structure via a solid state reaction [19-20]. The addition
of monoclinic ZrO2 suppressed the reduction of the Ta species
during nitridation at high temperature. Therefore, the
hydrogen evolution reaction under visible light irradiation
with sacrificial reagent was enhanced. Although TaON alone
cannot perform overall water splitting, it can be coupled with a
Z-scheme water splitting system with a shuttle redox mediator
to perform the overall water splitting reaction. Higashi et al.
utilized Pt-TaON (hydrogen evolution photocatalyst) and
RuO2-TaON (oxygen evolution photocatalyst) to produce the
overall water splitting reaction with an I-
/IO3-
shuttle redox
mediator [66]. Although the activity was low with 0.1-0.2%
apparent quantum efficiency, the photo catalyst was the first
example of a d0
oxynitridephotocatalyst. Another type of
oxygen evolution photocatalyst, Pt-WO3,was used with Pt-
TaON by Abe et al. in a similar system [67]. Better selectivity
of water oxidation to O2 and reduction of IO3-
to I-
was
achieved even if the solution contained a high amount of I-
. In
addition, the photocatalytic system yielded a steady water
splitting reaction under weak acid or neutral conditions even
under prolonged irradiation.
In addition to nitride photocatalyst, sulfide photocatalysts such
as CdS and ZnSare another type of anionic doped
photocatalysts that have gained significant attention in this
research area. As demonstrated by Sathish et al. [68], CdS can
be prepared by precipitation from Na2S and Cd(NO3)2,
followed by calcination. An activity of 450 μmol/g.h was
reported for the CdS prepared. Mesoporous CdS was also
prepared via ultrasonic mediated precipitation at room
temperature to form a particle size 4-6 nm using zeolite as the
template for precipitation [69]. These three methods form CdS
particles with different particle sizes and surface areas. CdS
prepared via the ultrasonic method yielded the highest UV
irradiated water splitting activity. This result indicates that the
water splitting activity can be correlated with particle size and
surface area. CdS supported on MgO and Al2O3was also
synthesized to study the effect of the support onphotocatalytic
water splitting. Depending on the CdS loading and template
that formed the CdS, the hydrogen evolution was higher than
for the unsupported CdS. In general, the MgO supported CdS
exhibited higher photoactivity compared with the Al2O3
supported CdS because of the basic nature of MgO. In
addition, noble metal doping such as with Pt further enhances
the hydrogen evolution rate to 14.15 mmol/g.h. CdS
undergoes photocorrosion and therefore is not stable under
prolonged light irradiation. By loading CdS on an appropriate
support, the photocatalytic water splitting initiated by CdS can
be enhanced without eluting S2-
into the reaction medium.
Loading CdS on ZTP (zirconium titanium phosphate) was
performed by Parida et al. to synthesize a visible light
photocatalyst[70]. CdS-ZTP was synthesized via ion exchange
and subsequent sulfurization with sodium sulfide, and 15wt%
CdS-ZTP was observed to yield the highest hydrogen
evolution rate with an apparent quantum efficiency of 5.84%
using a sulfide solution as the sacrificial reagent. Choi et al.
synthesize a Ni/NiO/KNbO3/CdS nanocomposite for visible
light hydrogen evolution in the presence of isopropanol [71].
At an appropriate amount of CdS and other components,
enhanced hydrogen evolution was observed because charge
recombination was suppressed in the reaction. CdS
nanoparticles dispersed in SBA-15 observed by Lunawat et al.
enhanced the photoactivity compared with bulk CdS[5]. SBA-
15 was added to cadmium acetate in H2S flow to form a
CdS/SBA-15 photocatalyst. A subsequent study indicated that
by doping CdS/SBA-15 with noble metals such as Pt, the
hydrogen evolution reaction rate could be greatly enhanced to
800 μmol/g.h. Shemesh et al. synthesize CdS-PdO and CdS-
Pd4S via the aqueous condensation of Pd2+
onto CdS nanorods
and high-temperature organic-phase synthesis, respectively
[72]. Due to efficient charge separation, the hydrogen
evolution rate of these photo catalysts was higher than that of
bulk CdS with 3.25% apparent quantum efficiency being
achieved. In addition, CdS has also been dispersed on a
hydrophobic polymer sheet, as described in the work of
Lunawat et al. [73]. Good adhesion of CdS nanoparticles on
the polymer enabled the photocatalyst to perform long life
photocatalytic water splitting. Separation of the photocatalyst
and the reaction medium was much easier compared with the
use of a powder photocatalyst. A polymer supported
nanocomposite of CdS-ZnS was also studied by Deshpande et
al. [74]. Good dispersion of nano-sized CdS particles in the
range of 1-3 nm was achieved when ZnS was present to assist
coating on polymer strip. Therefore, the water splitting
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activity was increased because the hydrogen evolution rate
was observed to be inversely proportional to the CdS particle
size. CdS was also synthesized with ZnO and ZnS to form a
hetero structure photocatalyst that was highly active in visible
light driven hydrogen evolution. The photocatalyst(ZnO)2-
(ZnS)1-(CdS)1, as reported by Wang et al. [75], yields a
hydrogen evolution rate up to 2790 μmol/g.husingSO3
2-
and
S2-
ions as sacrificial reagents. Photoexcited electrons in this
photocatalyst were also observed to have long lifetime (>225
ns), which contribute to the production of hydrogen. Another
study reported by Navarro et al. using a CdS-ZnO-CdO
photocatalyst developed from sequential precipitation and
thermal annealing investigated the photocatalytic hydrogen
evolution [35]. Thermal treatment significantly affected the
crystallinity and visible light absorption of the photocatalyst.
Appropriate thermal treatment improved the physical charge
separation and allowed more visible light of different
wavelengthsto be absorbed. The addition of cocatalysts such
as Ru and Pt enhanced the hydrogen evolution. Ru appeared to
be a better candidate for the cocatalyst because RuO2 particles
have better interaction with CdS particles, which reduces
charge recombination.
In addition to the combination with CdS to form a
photocatalyst, ZnS with a band gap of 3.6 eVis also a type of
sulfide photocatalyst. Jang et al. synthesize mesoporous ZnS
nano plates via a solvo thermal method using ethylenediamine
and calcination [76]. In their study, the calcination
temperature affected the hydrogen production but did not
appear to be correlated with surface area. The rate of hydrogen
evolution was observed to be highest for the mesoporous ZnS
calcined at 500°C. Using ultrasonic spray pyrolysis (USP),
Bang et al. developed ZnS: Ni2+
hollow microspheres and
nanoparticles [77]. Ni2+
formed a new energy level in the ZnS
band structure that was capable of absorbing visible light to
550 nm. Nanoparticle ZnS: Ni2+
had higher hydrogen evolution
activity than hollow microspheres regardless of the larger
surface area, most likely due to charge recombination at their
surface defects. Nevertheless, the researchers suggested that a
balance between optimal crystallinity and surface area is
necessary for photo excited electrons to induce photo
oxidation at the photocatalyst surface. In addition, Wu et al.
prepared(AgIn)xZn2(1−x)S2 solid solutions via a complete
aqueous route [78]. A band gap between 2.11-2.45 eV and a
broad absorption band in the visible region were reported.
Hydrogen evolution in sacrificial reagents yielded a rate of680
μmol/g.h and the photoactivity was sustained for at least 100
hours. Highly visible light active porous ZnS-In2S3-
CuSnanosphereswere produced by Li et al. via a facile one-pot
solvothermal method[79]. Without adding a cocatalyst,
ZnIn0.25Cu0.02S1.395was prepared at180°C for 18 hto achieve a
360 mmol/g.h hydrogen evolution rate and a 22.6% apparent
quantum yield at 420nm. Such excellent hydrogen evolution
performance was attributed to the high surface area that could
accommodate more active sites at the surface, a porous
structure that enhanced photo oxidation and photo reduction,
and efficient charge separation. Cu also plays an important
role because of its higher light absorption rate.
4. FUTURE RESEARCH DIRECTION
Significant research has been performed to improve
photocatalytic water splitting to produce hydrogen. However,
the water splitting efficiency is not high enough for the
emergence of a hydrogen economy via clean hydrogen
production. The research concentrated on finding visible light
responsive photocatalyst should be continued because of the
higher solar energy content in the visible light region. The
synthesis of inexpensive and efficient photocatalysts is crucial,
and the photocatalyst must be produced in abundance to
produce enough hydrogen to replace fossil fuels. Silicon
appears to be the most abundant material with properties of a
semiconductor and could provide direction in the search for
usable photo catalysts. Limited research has been conducted
on silicon based photocatalysts [80-82]. Nevertheless, great
potential in silicon-based photocatalysts is foreseen to harvest
solar energy, and more research should be performed. In
addition, anionic modification appears to be a promising band
engineering technology to harvest visible light from solar
energy. Sulfide and oxy(nitride) photocatalysts should be
further improved to achieve higher quantum efficiencies.
Furthermore, various strategies such as the combination of
anionic–cationic modification in photocatalyst synthesis and
the application of a Z-scheme system for water splitting
reactions could be used in creating the ultimate photocatalyst.
CONCLUSIONS
Cationic and anionic modification of semiconductors is
successfully employed in band engineering using different
types of preparation methods such as hydrothermal, solid state
reactions and polymerized complex methods for the purpose
of improving the photocatalytic water splitting reaction.
Enhanced hydrogen evolution has been achieved by
broadening absorption of the light wavelength, efficient
charge separation and the formation of a new band level to
facilitate the mechanism of the water splitting reaction. This
review also indicates the trend of utilizing visible light
irradiation in the water splitting reaction. Although the
hydrogen rate is not yet comparable to that of UV light
irradiation, visible light sensitive photocatalysts have greater
potential because solar irradiation mostly consists of the
visible spectrum. Further research should be performed
concerning various strategies to enable a hydrogen economy
to be realized as soon as possible before irreversible damage
done onto environment by a fossil fuel based economy.
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Volume: 02 Issue: 11 | Nov-2013, Available @ http://www.ijret.org 203
ACKNOWLEDGMENTS
The authors wish to express appreciation to theMyBrain
15Programme, USM Short Term Grant (Grant No. 60311051)
for the financial support provided.
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