This document introduces an Organic Redox Flow Battery (ORBAT) that uses water-soluble organic redox couples instead of heavy metals like vanadium for large-scale electrical energy storage. It demonstrates the rechargeability of an ORBAT cell using anthraquinone-2-sulfonic acid or anthraquinone-2,6-disulfonic acid on the negative electrode and 1,2-dihydrobenzoquinone-3,5-disulfonic acid on the positive electrode. Key advantages of ORBAT are its low cost due to inexpensive organic materials, sustainability without heavy metals or toxic materials, and high efficiency due to fast charge transfer kinetics of organic redox couples like quinones.
Edinburgh | May-16 | Future Battery Chemistries – The Rôle of SodiumSmart Villages
This document summarizes sodium-ion battery chemistry and its potential advantages over lithium-ion batteries. Sodium-ion batteries have similar properties to lithium-ion batteries due to the similarities between sodium and lithium. However, sodium-ion batteries also have some unique features such as stronger tendencies for layered electrode structures and access to the Fe3+/Fe4+ redox couple. Sodium-ion batteries could be lower cost than lithium-ion batteries due to sodium's abundance and the lack of need for copper current collectors. Their performance is promising and in some cases rivals that of lithium-ion batteries.
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.
At PreScouter, we help Fortune 500 clients quickly get up-to-speed on what they need to know to understand their options. PreScouter's Inquiry Service is a new, custom approach to ask science-based questions with a Ph.D. researcher through a brief video call. The results are debriefed in a meeting within two business days. This app provides clients with technically relevant, actionable information to further business objectives on a recurring basis.
In this inquiry, a client needed to identify Pre-Series B (or research teams) in the battery space that has a proprietary technology. PreScouter found 13 different batteries. Very soon, we should see a massive change in the ability to safely store and release power. Batteries explored include, but are not limited to: solid-state lithium-ion batteries, magnesium batteries, graphene car batteries, laser-made micro-supercapacitors, Na Ion batteries, and one of the fastest battery packs, LumoPack. PreScouter concluded this R&D injury with suggested next steps.
The document discusses using molecular dynamics simulations to investigate ion transport properties in solid polymer electrolytes (SPEs) and liquid electrolytes for battery applications. The simulations examined the coordination and diffusivity of lithium, sodium, magnesium, potassium, chloride, and fluoride ions in polyethylene oxide (PEO) polymer electrolytes and dimethyl ether liquid electrolytes. The results showed that ion diffusion was generally higher in the liquid electrolyte, while larger ions like sodium and potassium diffused more quickly in the polymer electrolyte than smaller lithium ions. The study provides a way to screen electrolyte materials for batteries using molecular dynamics simulations.
Rechargeable Sodium-ion Battery - The Future of Battery DevelopmentDESH D YADAV
This document provides an overview of rechargeable sodium-ion batteries and their potential as an alternative to lithium-ion batteries. Sodium-ion batteries offer lower costs due to sodium's nearly unlimited supply compared to lithium. However, their commercial development has been hampered by electrode materials that swell significantly during charging and discharging. Researchers have now developed a composite material made of molybdenum disulfide and graphene nanosheets that shows potential as a sodium-ion battery anode by resisting the swelling reaction. This flexible paper electrode is also the first demonstrated to work at room temperature in a sodium-ion battery anode.
This document reviews direct ethanol fuel cells (DEFCs) and their challenges. DEFCs are a type of alkaline fuel cell that can use ethanol as a fuel. They have some advantages over direct methanol fuel cells, but also face challenges including slow electrocatalysis kinetics, ethanol crossover through membranes, and issues with water and heat management. Improvements have been made to catalysts, membrane materials, and cell designs, but further addressing these challenges is still needed to improve DEFC performance and durability.
Photoelectrochemical splitting of water for hydrogen generation: Basics & Fut...RunjhunDutta
This document discusses photoelectrochemical (PEC) splitting of water for solar hydrogen generation. PEC is an environmentally safe process that uses solar energy and water to generate hydrogen fuel without undesirable byproducts. It has potential for both large and small-scale hydrogen production. The document outlines the basic principles and working of a PEC cell, which involves using a semiconductor photoelectrode to absorb light and drive water splitting reactions at the electrode surfaces to produce hydrogen and oxygen gases. It discusses factors that affect PEC cell performance and various strategies to modify materials and surfaces/interfaces to enhance efficiency. The document concludes that PEC is a promising but still developing technology that requires continued advances in materials science and engineering to optimize large-scale
Edinburgh | May-16 | Future Battery Chemistries – The Rôle of SodiumSmart Villages
This document summarizes sodium-ion battery chemistry and its potential advantages over lithium-ion batteries. Sodium-ion batteries have similar properties to lithium-ion batteries due to the similarities between sodium and lithium. However, sodium-ion batteries also have some unique features such as stronger tendencies for layered electrode structures and access to the Fe3+/Fe4+ redox couple. Sodium-ion batteries could be lower cost than lithium-ion batteries due to sodium's abundance and the lack of need for copper current collectors. Their performance is promising and in some cases rivals that of lithium-ion batteries.
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.
At PreScouter, we help Fortune 500 clients quickly get up-to-speed on what they need to know to understand their options. PreScouter's Inquiry Service is a new, custom approach to ask science-based questions with a Ph.D. researcher through a brief video call. The results are debriefed in a meeting within two business days. This app provides clients with technically relevant, actionable information to further business objectives on a recurring basis.
In this inquiry, a client needed to identify Pre-Series B (or research teams) in the battery space that has a proprietary technology. PreScouter found 13 different batteries. Very soon, we should see a massive change in the ability to safely store and release power. Batteries explored include, but are not limited to: solid-state lithium-ion batteries, magnesium batteries, graphene car batteries, laser-made micro-supercapacitors, Na Ion batteries, and one of the fastest battery packs, LumoPack. PreScouter concluded this R&D injury with suggested next steps.
The document discusses using molecular dynamics simulations to investigate ion transport properties in solid polymer electrolytes (SPEs) and liquid electrolytes for battery applications. The simulations examined the coordination and diffusivity of lithium, sodium, magnesium, potassium, chloride, and fluoride ions in polyethylene oxide (PEO) polymer electrolytes and dimethyl ether liquid electrolytes. The results showed that ion diffusion was generally higher in the liquid electrolyte, while larger ions like sodium and potassium diffused more quickly in the polymer electrolyte than smaller lithium ions. The study provides a way to screen electrolyte materials for batteries using molecular dynamics simulations.
Rechargeable Sodium-ion Battery - The Future of Battery DevelopmentDESH D YADAV
This document provides an overview of rechargeable sodium-ion batteries and their potential as an alternative to lithium-ion batteries. Sodium-ion batteries offer lower costs due to sodium's nearly unlimited supply compared to lithium. However, their commercial development has been hampered by electrode materials that swell significantly during charging and discharging. Researchers have now developed a composite material made of molybdenum disulfide and graphene nanosheets that shows potential as a sodium-ion battery anode by resisting the swelling reaction. This flexible paper electrode is also the first demonstrated to work at room temperature in a sodium-ion battery anode.
This document reviews direct ethanol fuel cells (DEFCs) and their challenges. DEFCs are a type of alkaline fuel cell that can use ethanol as a fuel. They have some advantages over direct methanol fuel cells, but also face challenges including slow electrocatalysis kinetics, ethanol crossover through membranes, and issues with water and heat management. Improvements have been made to catalysts, membrane materials, and cell designs, but further addressing these challenges is still needed to improve DEFC performance and durability.
Photoelectrochemical splitting of water for hydrogen generation: Basics & Fut...RunjhunDutta
This document discusses photoelectrochemical (PEC) splitting of water for solar hydrogen generation. PEC is an environmentally safe process that uses solar energy and water to generate hydrogen fuel without undesirable byproducts. It has potential for both large and small-scale hydrogen production. The document outlines the basic principles and working of a PEC cell, which involves using a semiconductor photoelectrode to absorb light and drive water splitting reactions at the electrode surfaces to produce hydrogen and oxygen gases. It discusses factors that affect PEC cell performance and various strategies to modify materials and surfaces/interfaces to enhance efficiency. The document concludes that PEC is a promising but still developing technology that requires continued advances in materials science and engineering to optimize large-scale
This document summarizes the principles and components of sodium-ion batteries. Some key points include:
- Sodium-ion batteries use sodium ions as charge carriers and have the advantages of low cost and abundance compared to lithium-ion batteries.
- Potential anode materials include porous carbon, tin, antimony, and alloys with additives like phosphorus or germanium. Cathode materials under research include oxides, fluorides, and polyanion compounds.
- A SnO/carbon nanocomposite showed promising results as an anode with good cycling stability and capacity retention. The mineral eldfellite has also been investigated as a potential sodium-ion battery cathode material.
- Sodium-
This document provides background on electrodialytic water splitting technology. The process uses bipolar ion exchange membranes along with cation and anion exchange membranes to convert water soluble salts into their corresponding acids and bases when a direct current is applied. The process is energy efficient as it does not involve electrochemical transformations. The key components and operating principles are described, including the role of the bipolar membrane in splitting water and generating hydrogen and hydroxide ions. Design considerations for optimizing the process such as current density, membrane area, and energy requirements are also discussed.
This is the academic presentation by Rahmandhika Firdauzha Hary Hernandha for Materials for Energy Storage and Conversion Device course in National Chiao Tung University, Taiwan. The slides based on an academic paper in Electrochem. Soc. Interface, 2016, 25(3), 85-87 by Stefano Passerini and Bruno Scrosati with other 10 papers as supporting information and images.
Transient Absorption Spectrometry in Photoelectrochemical Splitting of Water RunjhunDutta
Detailed Description of Application of Transient Absorption Spectrometry in Photoelectrochemical Splitting of Water for studying the electron-hole pair recombination in semiconductor.
[Illustrated with examples (Reference: Research Papers)]
This document summarizes manipulation strategies for two-dimensional amorphous nanomaterials (2D ANMs) to enhance their performance in electrochemical energy storage and conversion applications. It discusses two main categories of manipulation: 1) geometric configuration design, including spatial structure design (e.g. creating porous structures) and coordination environment design (e.g. defect creation); and 2) component interaction, including elemental doping/coupling and heterophase compositing. Recent examples manipulating 2D ANMs through these approaches for applications in batteries, supercapacitors and electrocatalysis are reviewed. The document concludes by discussing opportunities to further optimize manipulation of 2D ANMs.
1. The document describes a new nanohybrid material composed of polyoxomolybdate, polypyrrole, and graphene oxide for use as a high-power symmetric supercapacitor electrode.
2. The nanohybrid was synthesized via a one-pot reaction where polyoxomolybdate acted as an oxidizing agent to polymerize pyrrole monomers onto graphene oxide nanosheets.
3. Structural and morphological analysis showed the nanohybrid had an excellent architecture with good interfacial contact between components, enabling fast redox reactions for high capacitive performance.
The document discusses the design of new cathode materials for secondary lithium ion batteries. It provides background on the development of batteries over time and describes the basic components and operation of lithium ion batteries. Current commercially used cathode materials like lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium iron phosphate are described. Research aims to develop new cathode materials with improved properties like higher energy density, longer lifespan, lower cost, and environmental friendliness. Promising candidates include olivine-based phosphates and transition metal oxides.
The document discusses different types of batteries used in consumer electronics. It begins by noting the rising demand for battery materials. It then provides an overview of primary and secondary batteries, their basic components and chemical reactions, as well as common chemistries like carbon-zinc, alkaline, nickel-cadmium, nickel-metal hydride, and lithium-ion. The document concludes by discussing future battery research areas like nanotechnology and possibilities like micro batteries and paper batteries.
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.
A review on ipce and pec measurements and materials p.basnetPradip Basnet
The slides show how to measure the photoelectrochemical (PEC) properties of a light-active photocatalyst (usually semiconductor) and current literature summary for water splitting using sunlight.
Lithium ion battery and sodium ion batteryShehzadkhan101
This document outlines a student's MS thesis project on lithium-ion and sodium-ion batteries. It discusses the working principles, characteristics, and structures of these batteries. The student's project will cover battery types and lithium-ion battery charging/discharging processes. Sodium-ion batteries offer lower costs than lithium-ion due to more abundant materials, making them promising for large-scale energy storage.
Microbial fuel cell – for conversion of chemical energy to electrical energyrita martin
A microbial fuel cell (MFC) is a bio-electrochemical system that converts the chemical energy in the organic compounds/renewable energy sources to electrical energy/bio-electrical energy through microbial catalysis at the anode under anaerobic conditions. This process is becoming attractive and alternative methodology for generation of electricity. MFC can convert chemical energy directly into electricity without an intermediate conversion into mechanical power. MFC as various benefits Clean; Safe and quiet performance High energy efficiency and It is easy to operate, Electricity generation, Biohydrogen production, Wastewater treatment, Bioremediation .
NaS batteries show potential as an energy storage solution due to their high efficiency and power/energy density. However, their high operating temperature poses fire hazards. Researchers are working to reduce the temperature to improve safety and lower costs. Sodium and sulfur are abundant materials, and NaS batteries have a longer lifetime than lithium-ion batteries. Mass production and larger-scale applications may also help reduce the overall cost of NaS batteries.
The document discusses microbial fuel cells (MFC) for sustainable wastewater treatment. MFCs use microorganisms to convert the chemical energy in organic compounds into electricity. They offer direct conversion of energy in organic matter into electricity with potential for higher efficiency. MFCs can generate electricity while removing over 90% of chemical oxygen demand from wastewater. Several factors like temperature, ionic strength and cathode material affect MFC performance. MFCs show potential for cost-effective and energy-saving wastewater treatment.
This document summarizes a study that used microbial fuel cells prepared with freshwater sediments from the Rio de la Plata river to produce electricity. The study examined the relationship between current production and changes in the anodophilic microbial community. Microbial communities from the river sediments were able to produce current densities of up to 22.1 mA/m2. Analysis of the anodophilic microbial communities showed that those attached to the anode in fuel cells with added acetate substrate had greater diversity than those without added acetate.
Lithium-ion batteries were first proposed in the 1970s but were not successfully created until the mid-1980s. The first commercial lithium-ion battery was launched by Sony in 1991. Lithium-ion batteries use lithium compounds in the anode and a lithium cobalt oxide or lithium iron phosphate cathode. During discharge, lithium ions move from the anode to the cathode and back during charging through an electrolyte. Lithium-ion batteries have a high energy density and output voltage, long cycle life, and are more environmentally friendly than alternatives. However, they are also more expensive and require temperature monitoring and sealing to prevent issues.
The document discusses different types of fuel cells including hydrogen fuel cells, microbial fuel cells (MFCs), and polymer electrolyte membrane (PEM) fuel cells. It provides details on their working principles, components, and reactions. Hydrogen fuel cells combine hydrogen and oxygen to produce electricity, heat, and water. MFCs use microorganisms and organic substrates to generate electricity. PEM fuel cells are currently leading technology for vehicles and applications, using a proton-conducting polymer membrane and platinum catalysts.
The document describes a study that uses design of experiments (DoE) to optimize slurry-cast cathodes for solid-state batteries. Various combinations of polymer binder type and content and conductive carbon additive type and content were tested as cathode composites. Electrochemical and mechanical performance data from the experiments were analyzed using statistical software to identify optimal combinations. The predictions identified polyisobutene as the best binder and vapor-grown carbon fibers as the best additive to maximize specific capacity. Hydrogenated nitrile butadiene rubber and vapor-grown carbon fibers provided the best combination to maximize capacity retention. Additional tests were conducted to understand changes during cycling.
This document discusses novel materials for batteries. It begins by introducing solid state batteries and the requirements for electrode materials, including low working potential, high specific capacity, good interface with electrolytes, and high electrode kinetics. It then discusses various materials that could be used as electrodes, including lithium carbon electrodes using graphite and graphite intercalation compounds. Different types of graphite like natural, synthetic, and HOPG are described. The document also discusses intercalation of lithium ions into carbon and potential carbon-sodium electrodes. Finally, it discusses various material classes like rutile, perovskite, and spinel materials that could be used as cathodes in rechargeable lithium ion batteries. Specific
Special topic seminar microbial fuel cellsprasuna3085
The document discusses microbial fuel cells (MFCs), which use bacteria to generate electricity from organic waste. It begins with an introduction to MFCs and their potential applications. It then provides a brief history of MFCs, describes different types of MFCs and their basic working principle. The document also summarizes several research papers on MFCs and concludes with potential applications of MFCs in wastewater treatment, desalination, hydrogen production, powering remote sensors, and more.
This document provides an introduction to lithium battery technology, focusing on lithium ion batteries. It discusses the chemistry and features of lithium metal primary batteries and lithium ion secondary batteries. Lithium ion batteries have benefits like being rechargeable and having high energy density, but also drawbacks like fire potential if not properly designed. The document examines battery failure mechanisms like thermal runaway and the deposition of lithium metal. It analyzes the different classes of battery fires and properties of lithium ion cell burns, noting they can involve multiple fire classes and the release of flammable and toxic gases. EUCAR hazard levels for batteries are presented, ranging from no effect to explosion. Fire suppression methods are also briefly mentioned.
Uni.System™,A Breakthrough Vanadium Flow Battery for Grid-Scale Applications. Research at the Pacific Northwest National Laboratory (PNNL), plus the availability of commercial - "off the shelf" - components, has allowed the reliable vanadium flow battery energy storage system to be containerized, produced in volume, and available for onsite and large grid applications.
This document summarizes the principles and components of sodium-ion batteries. Some key points include:
- Sodium-ion batteries use sodium ions as charge carriers and have the advantages of low cost and abundance compared to lithium-ion batteries.
- Potential anode materials include porous carbon, tin, antimony, and alloys with additives like phosphorus or germanium. Cathode materials under research include oxides, fluorides, and polyanion compounds.
- A SnO/carbon nanocomposite showed promising results as an anode with good cycling stability and capacity retention. The mineral eldfellite has also been investigated as a potential sodium-ion battery cathode material.
- Sodium-
This document provides background on electrodialytic water splitting technology. The process uses bipolar ion exchange membranes along with cation and anion exchange membranes to convert water soluble salts into their corresponding acids and bases when a direct current is applied. The process is energy efficient as it does not involve electrochemical transformations. The key components and operating principles are described, including the role of the bipolar membrane in splitting water and generating hydrogen and hydroxide ions. Design considerations for optimizing the process such as current density, membrane area, and energy requirements are also discussed.
This is the academic presentation by Rahmandhika Firdauzha Hary Hernandha for Materials for Energy Storage and Conversion Device course in National Chiao Tung University, Taiwan. The slides based on an academic paper in Electrochem. Soc. Interface, 2016, 25(3), 85-87 by Stefano Passerini and Bruno Scrosati with other 10 papers as supporting information and images.
Transient Absorption Spectrometry in Photoelectrochemical Splitting of Water RunjhunDutta
Detailed Description of Application of Transient Absorption Spectrometry in Photoelectrochemical Splitting of Water for studying the electron-hole pair recombination in semiconductor.
[Illustrated with examples (Reference: Research Papers)]
This document summarizes manipulation strategies for two-dimensional amorphous nanomaterials (2D ANMs) to enhance their performance in electrochemical energy storage and conversion applications. It discusses two main categories of manipulation: 1) geometric configuration design, including spatial structure design (e.g. creating porous structures) and coordination environment design (e.g. defect creation); and 2) component interaction, including elemental doping/coupling and heterophase compositing. Recent examples manipulating 2D ANMs through these approaches for applications in batteries, supercapacitors and electrocatalysis are reviewed. The document concludes by discussing opportunities to further optimize manipulation of 2D ANMs.
1. The document describes a new nanohybrid material composed of polyoxomolybdate, polypyrrole, and graphene oxide for use as a high-power symmetric supercapacitor electrode.
2. The nanohybrid was synthesized via a one-pot reaction where polyoxomolybdate acted as an oxidizing agent to polymerize pyrrole monomers onto graphene oxide nanosheets.
3. Structural and morphological analysis showed the nanohybrid had an excellent architecture with good interfacial contact between components, enabling fast redox reactions for high capacitive performance.
The document discusses the design of new cathode materials for secondary lithium ion batteries. It provides background on the development of batteries over time and describes the basic components and operation of lithium ion batteries. Current commercially used cathode materials like lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium iron phosphate are described. Research aims to develop new cathode materials with improved properties like higher energy density, longer lifespan, lower cost, and environmental friendliness. Promising candidates include olivine-based phosphates and transition metal oxides.
The document discusses different types of batteries used in consumer electronics. It begins by noting the rising demand for battery materials. It then provides an overview of primary and secondary batteries, their basic components and chemical reactions, as well as common chemistries like carbon-zinc, alkaline, nickel-cadmium, nickel-metal hydride, and lithium-ion. The document concludes by discussing future battery research areas like nanotechnology and possibilities like micro batteries and paper batteries.
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.
A review on ipce and pec measurements and materials p.basnetPradip Basnet
The slides show how to measure the photoelectrochemical (PEC) properties of a light-active photocatalyst (usually semiconductor) and current literature summary for water splitting using sunlight.
Lithium ion battery and sodium ion batteryShehzadkhan101
This document outlines a student's MS thesis project on lithium-ion and sodium-ion batteries. It discusses the working principles, characteristics, and structures of these batteries. The student's project will cover battery types and lithium-ion battery charging/discharging processes. Sodium-ion batteries offer lower costs than lithium-ion due to more abundant materials, making them promising for large-scale energy storage.
Microbial fuel cell – for conversion of chemical energy to electrical energyrita martin
A microbial fuel cell (MFC) is a bio-electrochemical system that converts the chemical energy in the organic compounds/renewable energy sources to electrical energy/bio-electrical energy through microbial catalysis at the anode under anaerobic conditions. This process is becoming attractive and alternative methodology for generation of electricity. MFC can convert chemical energy directly into electricity without an intermediate conversion into mechanical power. MFC as various benefits Clean; Safe and quiet performance High energy efficiency and It is easy to operate, Electricity generation, Biohydrogen production, Wastewater treatment, Bioremediation .
NaS batteries show potential as an energy storage solution due to their high efficiency and power/energy density. However, their high operating temperature poses fire hazards. Researchers are working to reduce the temperature to improve safety and lower costs. Sodium and sulfur are abundant materials, and NaS batteries have a longer lifetime than lithium-ion batteries. Mass production and larger-scale applications may also help reduce the overall cost of NaS batteries.
The document discusses microbial fuel cells (MFC) for sustainable wastewater treatment. MFCs use microorganisms to convert the chemical energy in organic compounds into electricity. They offer direct conversion of energy in organic matter into electricity with potential for higher efficiency. MFCs can generate electricity while removing over 90% of chemical oxygen demand from wastewater. Several factors like temperature, ionic strength and cathode material affect MFC performance. MFCs show potential for cost-effective and energy-saving wastewater treatment.
This document summarizes a study that used microbial fuel cells prepared with freshwater sediments from the Rio de la Plata river to produce electricity. The study examined the relationship between current production and changes in the anodophilic microbial community. Microbial communities from the river sediments were able to produce current densities of up to 22.1 mA/m2. Analysis of the anodophilic microbial communities showed that those attached to the anode in fuel cells with added acetate substrate had greater diversity than those without added acetate.
Lithium-ion batteries were first proposed in the 1970s but were not successfully created until the mid-1980s. The first commercial lithium-ion battery was launched by Sony in 1991. Lithium-ion batteries use lithium compounds in the anode and a lithium cobalt oxide or lithium iron phosphate cathode. During discharge, lithium ions move from the anode to the cathode and back during charging through an electrolyte. Lithium-ion batteries have a high energy density and output voltage, long cycle life, and are more environmentally friendly than alternatives. However, they are also more expensive and require temperature monitoring and sealing to prevent issues.
The document discusses different types of fuel cells including hydrogen fuel cells, microbial fuel cells (MFCs), and polymer electrolyte membrane (PEM) fuel cells. It provides details on their working principles, components, and reactions. Hydrogen fuel cells combine hydrogen and oxygen to produce electricity, heat, and water. MFCs use microorganisms and organic substrates to generate electricity. PEM fuel cells are currently leading technology for vehicles and applications, using a proton-conducting polymer membrane and platinum catalysts.
The document describes a study that uses design of experiments (DoE) to optimize slurry-cast cathodes for solid-state batteries. Various combinations of polymer binder type and content and conductive carbon additive type and content were tested as cathode composites. Electrochemical and mechanical performance data from the experiments were analyzed using statistical software to identify optimal combinations. The predictions identified polyisobutene as the best binder and vapor-grown carbon fibers as the best additive to maximize specific capacity. Hydrogenated nitrile butadiene rubber and vapor-grown carbon fibers provided the best combination to maximize capacity retention. Additional tests were conducted to understand changes during cycling.
This document discusses novel materials for batteries. It begins by introducing solid state batteries and the requirements for electrode materials, including low working potential, high specific capacity, good interface with electrolytes, and high electrode kinetics. It then discusses various materials that could be used as electrodes, including lithium carbon electrodes using graphite and graphite intercalation compounds. Different types of graphite like natural, synthetic, and HOPG are described. The document also discusses intercalation of lithium ions into carbon and potential carbon-sodium electrodes. Finally, it discusses various material classes like rutile, perovskite, and spinel materials that could be used as cathodes in rechargeable lithium ion batteries. Specific
Special topic seminar microbial fuel cellsprasuna3085
The document discusses microbial fuel cells (MFCs), which use bacteria to generate electricity from organic waste. It begins with an introduction to MFCs and their potential applications. It then provides a brief history of MFCs, describes different types of MFCs and their basic working principle. The document also summarizes several research papers on MFCs and concludes with potential applications of MFCs in wastewater treatment, desalination, hydrogen production, powering remote sensors, and more.
This document provides an introduction to lithium battery technology, focusing on lithium ion batteries. It discusses the chemistry and features of lithium metal primary batteries and lithium ion secondary batteries. Lithium ion batteries have benefits like being rechargeable and having high energy density, but also drawbacks like fire potential if not properly designed. The document examines battery failure mechanisms like thermal runaway and the deposition of lithium metal. It analyzes the different classes of battery fires and properties of lithium ion cell burns, noting they can involve multiple fire classes and the release of flammable and toxic gases. EUCAR hazard levels for batteries are presented, ranging from no effect to explosion. Fire suppression methods are also briefly mentioned.
Uni.System™,A Breakthrough Vanadium Flow Battery for Grid-Scale Applications. Research at the Pacific Northwest National Laboratory (PNNL), plus the availability of commercial - "off the shelf" - components, has allowed the reliable vanadium flow battery energy storage system to be containerized, produced in volume, and available for onsite and large grid applications.
Breakthrough technologies for the Base of the Pyramid (BoP), vol.2 (August 20...Anne-Laure Herrezuelo
Even the in the most remote areas of the world, people use mobile phone.
The number of mobile phone subscriptions has jumped from 12.4 million to more than 5 billion in the last 20 years. There are more phones than people on the planet, and some countries like Hong Kong boast 200% penetration. Panama has 202.5%, Saudi Arabia 169.5%, Russia 155%, Brazil 136%… Comparatively, the US have “only” 103% mobile penetration and Japan 95%.
It is even more significant in developing countries: the quickest expansion has been in the developing countries, with 3.8 billion new users.
ICT can provide expertise and information to BoP people who, without it, face physical or financial challenges to access to these resources. Continuously increasing connectivity can help people at the BoP and entrepreneurs to make significant changes in their life.
Changes are already happening.
Today, in 9 African countries - Cameroon, the Democratic Republic of Congo, Gabon, Kenya, Madagascar, Tanzania, Uganda, Zambia and Zimbabwe - have more mobile money accounts than bank accounts – championing financial inclusion by providing financial services to more people than traditional banks have been able to reach
Traditional BoP industries such as Agriculture - a more traditional BoP industry - are also disrupted. Innovative social businesses use ICT tools to gain productivity and also access to relevant data about products.
Learn which company are having a tremendous impacts on farmers by providing them with accurate market price information or useful weather forecasts.
Learn how an app has changed the life of 1 million people getting water at odd time only every 3 to 5 days, for about 4h/day.
Learn how mobile technologies has helped people getting better protected through micro-insurance system.
This document describes a simplified SPICE behavioral model for lithium-ion batteries. The model allows circuit designers to predict battery runtime and performance by modeling voltage over time at different charge and discharge rates. Key parameters like capacity, state of charge, and number of cells can be adjusted based on battery specifications. Examples are provided to demonstrate modeling charge/discharge times and voltage curves for sample battery configurations.
This presentation is an internship presentation which is carried out at Elpro Energy Dimensions Pvt. Ltd. Bangalore by Rajkumar Tondare
Vanadium Redox Flow Battery is a new challenging replacement to the conventional lead acid batteries and diesel generators.
Micro-grids supply energy to remote areas using multiple distributed energy sources and manage supply and demand complexities. They reduce transmission losses and relieve stress on the main grid. Various renewable technologies can be used including solar, wind, biomass and waste heat recovery. Energy storage helps provide steady backup power and balances intermittent renewable output. Communication controls coordinate supply and demand. Micro-grids provide reliable off-grid electrification with less need for grid upgrades.
Predicting Breakthrough Technologies: An empirical analysis of past predictio...Jeffrey Funk
These slides empirically analyzes predictions made by MIT’s Technology Review. Technology Review has produced a list of 10 breakthrough technologies for many of the last 10 years (2001, 2002-2014). These predictions are based on conversations with academic experts from a variety of scientific disciplines. To analyze these predictions, I gathered recent market sales data for the predictions done in 2001, 2003, 2004 and 2005. I found that many of these technologies still have small markets (<$1Billion), markets that are smaller than technologies not chosen by Technology Review such as smart phones, Cloud Computing. Tablet Computers. Big Data, Social Networking, and eBooks/eReaders. The slides then use theories of cognition to explain these relatively poor predictions and propose an alternative way of predicting breakthrough technologies
By Mr. Irish Pereira The current and expected usage of redox flow batteries across the World.
Includes usage of redox batteries in power generation sectors, including market trends.
Recent advancements in tuning the electronic structures of transitional metal...Pawan Kumar
The smooth transition from finite non-renewables to renewable energy conversion technologies will require efficient electrocatalysts which can harness intermittent energies to store in the form of chemical bonds. The oxygen evolution reaction (OER) impedes the widespread usage of water electrolyzers to convert H2O into H2 and persists as a bottleneck, including other energy conversion devices with sluggish four H+/e− kinetics. In this context, designing highly active and stable catalysts capable of driving a lower overpotential in the OER to produce continuous hydrogen (H2) is a primary demanded. This chapter discussed the mechanism of the OER in conventional adsorbate oxygen and lattice oxygen participation in transition metal oxides (TMOs). Further, the influences of surface engineering, doping, and defects in the TMOs and understanding the electronic structure to screen electrodes towards the structure–activity relationship are highlighted. Specifically, the adsorption strength of O 2p is understood in detail as its binding ability over the surface of TMOs can be correlated directly to the OER activity. The iterative development of TMOs in terms of understanding electronic structural attributes is essential for the commercial deployment of energy conversion technologies. The comprehensive outlook of this chapter investigates thoroughly how TMOs can be used as significant materials for the OER in the near future.
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
Sunlight-driven water-splitting using twodimensional carbon based semiconductorsPawan 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.
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 …
Water-splitting photoelectrodes consisting of heterojunctions of carbon nitri...Pawan Kumar
Quinary and senary non-stoichiometric double perovskites such as Ba2Ca0.66Nb1.34-xFexO6-δ (BCNF) have been utilized for gas sensing, solid oxide fuel cells and thermochemical CO2 reduction. Herein, we examined their potential as narrow bandgap semiconductors for use in solar energy harvesting. A cobalt co-doped BCNF, Ba2Ca0.66Nb0.68Fe0.33Co0.33O6-δ (BCNFCo), exhibited an optical absorption edge at ~ 800 nm, p-type conduction and a distinct photoresponse upto 640 nm while demonstrating high thermochemical stability. A nanocomposite of BCNFCo and g-C3N4 (CN) was prepared via a facile solvent assisted exfoliation/blending approach using dichlorobenzene and glycerol at a moderate temperature. The exfoliation of g-C3N4 followed by wrapping on perovskite established an effective heterojunction between the materials for charge separation. The conjugated 2D sheets of CN enabled better charge migration resulting in increased photoelectrochemical performance. A blend composed of 40 wt% perovskite and CN performed optimally, whilst achieving a photocurrent density as high as 1.5 mA cm-2 for sunlight-driven water-splitting with a Faradaic efficiency as high as ~ 88%.
The document discusses the synthesis and characterization of nickel-manganese phosphate (NiMn(PO4)2) as an electrode material for supercapattery devices. NiMn(PO4)2 nanocomposites were synthesized via a sono-chemical method and tested as the positive electrode in an asymmetric supercapattery device with activated carbon as the negative electrode. Electrochemical measurements showed the NiMn(PO4)2 electrode had a high specific capacitance of 678 C/g and the supercapattery device delivered a maximum specific energy of 63.8 Wh/kg and specific power of 11,892 W/kg, with 99.2% capacity retention after 5000 cycles. Analysis of the charge
Batteries play an essential role on most of the electrical equipment and electrical engineering tools. However, one of the drawbacks of lead acid batteries is PbSO4 accumulates on the battery plates, which significantly cause deterioration. Therefore, this study discusses the discharge capacity performance evaluation of the industrial lead acid battery. The selective method to improve the discharge capacity is using high current pulses method. This method is performed to restore the capacity of lead acid batteries that use a maximum direct current (DC) of up to 500 A produces instantaneous heat from 27°C to 48°C to dissolve the PbSO4 on the plates. This study uses an 840 Ah, 36 V flooded lead acid batteries for a forklift for the evaluation test. Besides, this paper explores the behavior of critical formation parameters, such as the discharge capacity of the cells. From the experimental results, it can be concluded that the discharge capacity of the flooded lead acid battery can be increase by using high current pulses method. The comparative findings for the overall percentage of discharge capacity of the batteries improved from 68% to 99% after the restoration capacity.
On the (pseudo) capacitive performance of jack fruit seed carboneSAT Publishing House
The document summarizes research on using carbon derived from jack fruit seeds (JFSC) as an electrode material for electrochemical capacitors. JFSC was produced by pyrolyzing jack fruit seeds under nitrogen atmosphere without activating agents. Characterization showed the JFSC has a microporous structure and contains nitrogen, sulfur, and oxygen functional groups. Electrochemical tests found the JFSC exhibits pseudocapacitive behavior in acid and neutral electrolytes. In sulfuric acid, it achieved a specific capacitance of 316 Fg-1 and retained 93% of its initial capacitance after 500 charge/discharge cycles. The research demonstrates the potential of using an agricultural waste like jack fruit seeds for electrode materials in electro
This document describes research into using alkaline zinc hydroxide solution as an electrolyte for hydrogen generation through water electrolysis. The solution is prepared by dissolving zinc oxide in sodium hydroxide or potassium hydroxide solutions, forming sodium zincate or potassium zincate. Experimental results showed that using these solutions as electrolytes can enhance the hydrogen evolution rate compared to conventional electrolytes. Specifically, sodium zincate increased the rate by a factor of 2.74 and potassium zincate by 1.47. The zincate solutions may improve ionic conductivity and electrode catalytic activity for hydrogen evolution. This research could help optimize alkaline water electrolysis systems for more efficient hydrogen production.
Multistage Activation of Anthracite Coal-Based Activated Carbon for High-Perf...GuanrongSong1
An anthracitic coal-derived activated porous carbon is proposed as a promising carbon electrode material for
supercapacitor (SC) applications. The specific capacitance of this activated carbon SC electrode is related to the characteristics, such
as specific surface area, pore size distribution, wettability, and conductivity. In the present work, a series of anthracite-based activated
carbons (ABAC) were prepared via a multistage activation process and used as electrode materials for SCs. The multistage activation
experiment was developed by exploring different activation temperatures, precursor/activating agent mass ratios, and process treating
environments. The electrochemical performance of ABACs was evaluated in a three-electrode testing system. Multiple electrolytes
were utilized, such as 1 M sulfuric acid (H2SO4) and 1 and 6 M potassium hydroxide (KOH) solutions. An optimum ABAC
electrode was obtained, characterized by its largest wettability and superior conductivity, and achieved excellent electrochemical
performance. The three-electrode system exhibited a specific capacitance of 288.52 and 260.30 F/g at 0.5 A/g in the 1 M H2SO4 and
6 M KOH electrolytes, respectively. It was found that moderate multistage activation temperatures are beneficial for the electrolyte
uptake which enhances the specific capacitance. The high content of the oxygen functional groups on the activated carbon surface
greatly improved its specific capacitance due to the increase in wettability. In the 1 M H2SO4 electrolyte, the working electrode
exhibited better performance than in 1 M KOH because the ion diameter in the acidic electrolyte was more suitable for pore
diffusion. The concentrated KOH electrolyte leads to an increase in specific capacitance due to increased ions being adsorbed by a
certain number of the hydrophilic pores. Moreover, the specific capacitance of the optimum ABAC sample remained at 95.4% of the
initial value after 1000 galvanostatic charge−discharge tests at 0.5 A/g, which is superior to the performance of SC grade commercial
carbon.
ev module 3.ppt.and notes of EV to kno6aAshokM259975
The document provides information on different types of batteries that can be used for electric vehicles (EVs) and hybrid electric vehicles (HEVs). It discusses the basics of lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, lithium polymer batteries, sodium-sulfur batteries, and zinc-air batteries. For each battery type, it describes the basic chemistry and reactions that occur during charging and discharging, as well as their advantages and disadvantages for use in EVs and HEVs.
Double layer energy storage in graphene a studytshankar20134
This document summarizes research on using graphene for energy storage in electrochemical double layer capacitors (EDLCs). Graphene has potential as an EDLC electrode material due to its high surface area and electrical conductivity. Studies have found specific capacitances of graphene electrodes ranging from tens of F/g to over 1000 F/g depending on preparation methods and electrolytes. However, graphene sheets tend to restack reducing surface area availability. Methods to prevent restacking like adding metal oxides or curving graphene sheets have improved capacitance. Research is optimizing graphene properties and composites to enhance energy and power densities for applications requiring high power such as filtering alternating current.
Computational screening of two dimensional materials for hydrogen evolution reactions
This presentation discusses screening 2D materials computationally for hydrogen evolution reactions. The document outlines the research methodology which involves searching potential 2D materials, assessing their dynamical stability, electronic properties, band edge diagrams, Gibbs free energy calculations, and optical properties. Several potential 2D materials are listed along with their bandgaps and charge mobilities. The goals are to reduce the bandgap of photoelectrodes, increase charge carrier mobility for photocatalysis, optimize Gibbs free energy values, and increase hydrogen adsorption efficiency.
This document discusses in situ irradiated X-ray photoelectron spectroscopy (ISIXPS) and its ability to investigate electron transfer mechanisms in S-scheme photocatalysts. S-scheme photocatalysts have shown promise for solar fuel production. ISIXPS is an effective technique for studying electron transfer pathways in S-scheme heterojunctions, but the mechanism by which it identifies these pathways is not fully understood. This document aims to provide insight into how ISIXPS can be used to confirm interfacial electron transfer and better understand the electron transfer mechanism in S-scheme photocatalysts.
The document discusses various types of energy storage and conversion devices including lithium cobalt oxide batteries, supercapacitors, fuel cells, and dye sensitized solar cells. It provides an introduction and overview of these topics, describing their basic components, mechanisms, and applications. Specifically, it outlines the syllabus for a course covering lithium cobalt oxide and metal air batteries, supercapacitors, and energy conversion devices like fuel cells and dye sensitized solar cells.
Depositacion electroforetica dentro de campos electricos moduladosMario ML
This document reviews electrophoretic deposition (EPD) under modulated electric fields such as pulsed direct current (PDC) and alternating current (AC). Classical EPD uses continuous direct current which can lead to issues depositing from aqueous suspensions due to water electrolysis. Modulated electric fields can reduce electrolysis and produce more uniform coatings. PDC and AC offer advantages over continuous DC like reducing bubble formation and particle aggregation. While deposition rates may decrease under modulated fields, they allow for depositing biochemical and biological materials in more active states. The document discusses EPD mechanisms and modulated field types, and their applications including in biotechnology.
The document discusses nanoparticles for small molecule electrocatalysis, specifically focusing on oxygen evolution reaction (OER) using Ni-Co hydroxides and oxides. It first provides background on OER and discusses how Co3O4, metal-doped Co3O4, and NiCo2O4 can be used as catalysts. It then outlines the purpose and scope of studying the composition dependence of Ni-Co hydroxides and oxides for OER using stainless steel mesh. The document reviews relevant theory around OER mechanisms and properties of different catalyst materials.
This document discusses solar hydrogen fuel cell technology. It begins by introducing the principles of the solar hydrogen energy cycle, where excess solar energy is used to produce hydrogen via electrolysis. The hydrogen can then be stored and used in a fuel cell to generate electricity when solar power is unavailable. The document then describes the key components of a solar hydrogen system, including photovoltaic panels, electrolyzers, hydrogen storage, fuel cells, and DC/AC inverters. It provides details on different types of electrolyzers and fuel cells, explaining their basic operations and applications. The goal is to explain the principles and interactions of the components in a solar hydrogen energy system.
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A empresa de tecnologia anunciou um novo smartphone com câmera aprimorada, maior tela e bateria de longa duração. O dispositivo também possui processador mais rápido e armazenamento expansível. O novo modelo será lançado em outubro por um preço inicial de US$799.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
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The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help boost feelings of calmness, happiness and focus.
This document provides an overview of the American Legislative Exchange Council (ALEC) and its influence in New Jersey. It finds that ALEC has introduced model legislation on issues like worker rights, education, voting rights, consumer rights, immigration, and the environment. Some key findings are that 11 New Jersey legislators have ties to ALEC leadership and hundreds of ALEC's model bills have been introduced in New Jersey, though few have passed. It also lists several major corporations with ties to ALEC that have dropped their support in recent years.
This document provides information about ALEC's influence in Arizona state politics. It finds that ALEC, which is funded primarily by corporations, has a significant presence in the Arizona legislature. Many legislators are ALEC members and some have received funding from an ALEC-affiliated "scholarship" fund to attend conferences, with the funds coming from corporate donors but not requiring disclosure of their sources. The report analyzes bills introduced in Arizona in 2013 and finds examples both directly from ALEC's legislative agenda and with similar intent to ALEC model bills. It concludes that ALEC continues to exert influence in shaping legislation in Arizona to benefit its corporate members.
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The Central Regional Advisory Council will hold a public meeting on December 9, 2011 at 1:00 pm at the MCSO Training Facility in Phoenix, Arizona. The agenda includes welcoming remarks, approving previous meeting minutes, updates from the Arizona Department of Homeland Security and ACTIC, discussing RAC guidelines and strategies, and grant extensions/modifications/reallocations. Time will also be provided for public comment and discussion of the next meeting date before adjourning.
2. A1372 Journal of The Electrochemical Society, 161 (9) A1371-A1380 (2014)
ples for achieving high power densities. However, the bromine-based
positive electrode presents some challenges with respect to handling
and use of bromine, and also bromine crossover from the positive
to the negative electrode. The use of a water-soluble organic redox
couple at the positive electrode that we have studied here has the clear
prospect of overcoming the foregoing problems. Non-aqueous solu-
tions of organic redox substances have been considered by Rasmussen
and Brushett.14,15
In this publication, we focus on understanding the
performance characteristics of a dual-aqueous feed organic flow bat-
tery and discuss the materials, challenges, and directions for further
research in this area.
Factors Governing the Operation of ORBAT
Charge-transfer processes.— The principal basis of an efficient
rechargeable redox flow battery is the rapid kinetics of charge-
transfer at the positive and negative electrodes. Many organic redox
couples, especially from the quinone family, undergo rapid proton-
coupled electron transfer without the need for dissociating high en-
ergy bonds. Consequently, these redox couples have relatively high
rate constants for the charge-transfer process. In general, we expect
molecules with conjugated carbon-carbon bonds and keto- and enol-
groups that allow for the delocalization and rearrangement of the
pi-electrons to undergo these redox transformations with extraordi-
nary facility.16
Typical organic redox couples are 1,2-benzoquinone-
3,5-disulfonic acid (BQDS) and anthraquinone-2-sulfonic acid (AQS)
(Eqs. 1 and 2).
HO3S SO3H
OH
OH
+ 2e-
+ 2H+
O
O
HO3S SO3H
E0
= + 0. 85 V
[1]
O
O
SO3H
OH
OH
SO3H
+ 2e-
+ 2H+
E0
= + 0.09 V
[2]
Such quinone-based redox couples have rate constants that are 2–
3 orders of magnitude higher than that of the vanadium ions in the
commercial vanadium redox system.17,18
Overpotential losses from
charge-transfer are expected to be low with these organic redox cou-
ples. As dissociation and rearrangement of C-C and C-H bonds do not
occur in these electrochemical reactions, high-surface area conductive
metal-free electrode surfaces, such as those based on carbon black, are
sufficient to support the charge-transfer process. No precious metal
electro-catalyst is required. Selecting the appropriate compounds with
fast rate constants (on the order of 10−3
to 10−4
cm s−1
) is necessary
when considering the technical viability of ORBAT.
Cell voltage.— The standard reduction potential of the redox cou-
ple is characteristic of the molecule and its specific substituent groups.
Since the standard reduction potential is also related to the electronic
energy of the molecular orbitals, the voltage of a redox flow cell is de-
termined by the difference in energy of the highest occupied molecular
orbital (HOMO) of redox couple used as the negative electrode mate-
rial and the lowest unoccupied molecular orbital (LUMO) of the redox
couple used as the positive electrode material. Previous experimen-
tal studies on quinones show that electron-withdrawing substituent
groups lower the energy levels of the HOMO and LUMO, while
electron-donating substituents raise the levels.19
Thus, we can use
substituent groups to selectively tune the standard reduction potential
of the quinone compounds to achieve the desired cell voltage. We may
use the Gibbs free-energy change for the reduction of the redox couple
with hydrogen, as estimated from quantum mechanical calculations,
to determine the standard reduction potential of the redox couples.
Being an aqueous battery, the voltage range for ORBAT is limited
by the oxygen evolution reaction at the positive electrode and the hy-
drogen evolution reaction at the negative electrode. Consequently, a
maximum cell voltage of 1.23 V is to be expected at room temperature.
However, by inhibiting the kinetics of the hydrogen evolution and oxy-
gen evolution reactions, we may achieve higher cell voltages. In this
respect, the non-aqueous systems have an advantage of being able to
provide a wider range of cell voltage. However, the inherent advantage
of lower cost and higher level of safety presented by aqueous systems
is particularly attractive for large-scale energy storage applications.
Mass transport processes.— To realize a low-cost battery, we must
be able to operate at high current densities without compromising volt-
age efficiency. With the rapid charge transfer processes in quinones,
the current density will be limited by mass transport of the reactants
and products. If a current density of 100 mA cm−2
is required at a
reactant concentration of 1 M, we may use the steady-state Nernst
diffusion layer model to estimate the mass transport coefficients to be
approximately 5 × 10−4
cm s−1
.20
Consequently, to maintain a cur-
rent density of 100 mA cm−2
with a redox couple that has a solubility
of 1 M and a diffusion coefficient of about 1 × 10−6
cm2
s−1
, the
solutions must be circulated past the electrodes so as to maintain a
thin diffusion layer of approximately 2 × 10−3
cm. Such a diffusion
layer thickness is in the practical range of values observed with rapid
circulation. Flow-through electrodes can lead to further reduction in
diffusion layer thickness.21,22
Thus, the diffusion coefficient and solu-
bility of the redox couple are principal properties for which the values
must be as high as possible for reaching the performance and cost
targets for large-scale energy storage applications.
In general, the un-substituted quinones exhibit limited solubility
in water. However, the solubility of the quinones can be increased
substantially by the incorporation of sulfonic acid and hydroxyl sub-
stituents. For example, benzoquinone has a solubility of 0.1 M, while
BQDS has a solubility of approximately 1.7 M at 25◦
C. Further
increases in solubility can be achieved by raising the temperature.
Therefore, achieving solubility values as high as 2 M is practical even
within the quinone family of compounds. Other organic redox couples
with high aqueous solubility include carboxylic acids and aromatic
heterocyclic compounds.8
Reactivity and long-term cycling.— Under acidic conditions, the
electro-reduction of quinones occurs often by a concerted proton trans-
fer and electron transfer process5
and no radical species are produced
as part of this redox process. Sometimes, the mechanisms could in-
volve sequential steps of protonation and electron transfer.23
Addi-
tionally, alkaline environments favor the formation of anion radicals
that tend to be reactive. Such formation of radicals in alkaline medium
is commonly encountered at about a pH of 9 and have lifetimes long
enough to be studied by electron spin resonance spectroscopy10,23–25
Another significant benefit of acidic over alkaline systems arises from
the absence of free cations besides the proton (or hydronium ion) in
the solutions. Thus, a proton exchange membrane electrolyte with
high ionic conductivity can be used. Inexpensive hydrocarbon mem-
branes such as polystyrenesulfonic acid, sulfonated polyetherether-
ketone and sulfonated polyethersulfone can also be used instead of
Nafion.26,27
Furthermore, the proton exchange membrane will inhibit
the transport of any anionic chemical species across the membrane
avoiding crossover of reactants from one side of the cell to another,
thereby avoiding self-discharge. Consequently, the long-cycle life re-
quirement of large-scale energy storage systems is more likely to be
realized with acidic systems.
For continuous operation at temperatures as high as 60◦
C the se-
lected organic compounds must have sufficient hydrolytic stability.
The quinones are generally quite stable in contact with oxygen. How-
ever, when the reduced form of the quinones (hydroquinones) in so-
lution come in contact with oxygen from air, the reduced form can be
re-oxidized to the quinone form. No permanent loss of material prop-
) unless CC License in place (see abstract).ecsdl.org/site/terms_useaddress. Redistribution subject to ECS terms of use (see198.27.89.56Downloaded on 2014-10-20 to IP
3. Journal of The Electrochemical Society, 161 (9) A1371-A1380 (2014) A1373
erties occurs as a result of such re-oxidation, and this process is just
like self-discharge. This self-discharge process can be prevented by
excluding access of the hydroquinones to oxygen. The quinones and
hydroquinones are generally stable at elevated temperatures of 60◦
C,
permitting faster diffusion to be achieved. In contrast, the vanadium
systems are very sensitive to such elevated temperature operation be-
cause of the numerous reactions between water and the vanadium oxo
ions. In some cases insoluble products such as vanadium pentoxide
are produced that negatively impact cycle life.5
Faradaic efficiency.— The potential for faradaic efficiency losses
are generally associated with the negative electrode in these types
of systems due to the proximity of the hydrogen evolution potential.
In the case of AQS, the standard reduction potential is about 100
millivolts positive to that of the normal hydrogen electrode (NHE).
Consequently, hydrogen evolution cannot occur readily during charge.
Additionally, the hydrogen evolution reaction is substantially inhib-
ited on carbon materials. This situation in ORBAT is to be contrasted
with the vanadium redox battery; the vanadium(III)/vanadium(II) cou-
ple operates at a potential approximately 0.350 volts negative to NHE
and hydrogen evolution occurs during normal charging of the battery.
Furthermore, the deposition of metallic impurities on the electrode fa-
cilitates hydrogen evolution and thus lowers the overall efficiency. By
avoiding the use of any soluble metal ions and only using carbon-based
electrodes ORBAT can achieve a faradaic efficiency close to 100%.
In the present study, we focus on understanding the performance
of ORBAT based on 1,2-benzoquinone-3,5-disulfonic acid (BQDS)
at the positive electrode with either anthraquinone-2-sulfonic acid
(AQS) or anthraquinone-2,6-disulfonic acid (AQDS) at the negative
electrode. To this end, we have measured the kinetic parameters for
charge-transfer, and diffusion coefficients for various redox couples in
acidic media. We have fabricated membrane-electrode assemblies and
measured the properties of flow cells over multiple cycles of charge
and discharge, and analysed these results in terms of the fundamental
properties discussed above.
Experimental
Electrochemical characterization.— Measurement of kinetic pa-
rameters and diffusion coefficients was conducted in a three-electrode
cell consisting of a rotating glassy carbon disk working electrode, a
platinum wire counter electrode, and a mercury/mercuric sulfate ref-
erence electrode (Eo
= +0.65 V). The quinones, in either the fully
reduced or fully oxidized form, were dissolved in 1 M sulfuric acid
to a concentration of 1 mM. The solutions were de-aerated and kept
under a blanket of argon gas throughout all the experiments. All mea-
surements were conducted in the potentiodynamic mode (Versastat
300 potentiostat) at a scan rate of 5 mV s−1
over a range of rotation
rates (500 rpm to 3000 rpm). Impedance measurements were also
made at each rotation rate. Cyclic voltammetry was conducted on a
static glassy carbon electrode at a scan rate of 50 mV s−1
.
Charge/discharge cycling of full ORBAT cells.— A flow cell was
constructed using fuel cell hardware that has graphite end plates (Elec-
trochem Inc.) and an electrode active area of 25 cm2
. The reactant was
circulated using peristaltic pumps (Masterflex) at a flow rate of approx-
imately 0.5–1.0 liter min−1
. Membrane electrode assemblies (MEA)
needed for the cell were fabricated in house using procedures similar
to those previously reported for direct methanol fuel cells.27
Specif-
ically, two sheets of carbon paper (Toray 030-non-teflonized) were
coated with an ink containing 0.1 g of Vulcan XC-72 carbon black
and 0.3 g of Nafion. The coated electrodes were hot pressed with a
Nafion 117 membrane to form a MEA. All full cell experiments were
carried out at 23◦
C. Two glass containers served as reservoirs for the
solutions of the redox couples. An argon flow was maintained above
these solutions to avoid reaction of the redox couples with oxygen.
The current-voltage characteristics of the cells were measured at vari-
ous states of charge. Charge/discharge studies were carried out under
constant current conditions.
Quantum mechanics-based calculations.— To determine E1/2 val-
ues, we used density functional theory to calculate the standard Gibbs
free energy change ( Go
) for the reduction of the oxidized form of
the redox couple. The calculations were performed at the B3LYP/
6-31+G(d,p) level of theory with thermal correction28
and implicit
consideration of water-solvation.29
The free energy correction for the
standard state of 1 atm in the gas phase and 1 M upon solvation was
applied, i.e. Gsolution = Ggas + 1.9 kcal · mol−1
at 298 K. Consid-
ering the lower pKa value of benzenesulfonic acid (pKa(sulfonic acid) =
–2.8),30
quinone sulfonic acid derivatives are expected to dissociate to
sulfonates in 1 M sulfonic acid aqueous solution. Go
was calculated
based on the reduction of quinone derivatives with H2. The stan-
dard electrode potential for the redox couple was deduced from Eo
=
– Go
/nF, where n is the number of protons involved in the reaction
and F is the Faraday constant.
Results and Discussion
Cyclic voltammetric measurements on AQS and AQDS show a sin-
gle step electrochemical reaction involving two electrons (Figures 2a
and 2b). Peak separations suggested AQDS was less kinetically re-
versible than AQS. The cyclic voltammograms for BQDS showed a
rapid oxidation step, but a slower reduction step (Figure 2c). The shape
of the reduction peak for BQDS suggested a possible slow chemical
step following electron transfer. Such a slow step is consistent with
the hydration process leading to the conversion of the hydroquinone to
1,4-benzoquinone-2-hydroxy-3,5-disulfonic acid, as reported by Xu
and Wen.10
The reversible potentials estimated from the anodic and
cathodic scans for the three compounds were in agreement with the
quantum mechanical calculations (Table I). The facile proton and elec-
tron transfer processes occurring on a glassy carbon electrode in the
absence of any catalyst confirmed an outer-sphere type of mechanism.
Linear sweep voltammetric measurements at a rotating disk elec-
trode at various rotation rates (Figure 3a–3c) showed that the limiting
current, Ilim, was found to depend linearly on the square root of the
rotation rate, ω, as per the Levich equation (Eq. 3).
Ilim = 0.62nF AD2/3
o ω1/2
ν−1/6
C∗
[3]
Where n is the number of electrons transferred, F, the Faraday
constant, A, electrode area, Do, the diffusion coefficient, ν, the kine-
matic viscosity of the solution and C*, the bulk concentration of the
reactants. For n = 2, an active electrode area of 0.1925 cm2
, and a
kinematic viscosity of the electrolyte of 0.01 cm2
s−1
, we were able
to evalulate the diffusion coefficient from the slope of the straight line
plots in Figure 3d.
To determine the kinetic parameters for the charge-transfer pro-
cess, namely the rate constant and the apparent transfer coeffcient, the
logarithm of the kinetic current (after correction for mass-transport
losses) was plotted against the observed overpotentials greater than
100 mV, where the Tafel equation is applicable (Eq. 4 and Figure 3e).
I
1 − I
Ilim
= Iex
CO
C∗
O
exp −
αnF(E − Erev)
RT
−
CR
C∗
R
exp
(1 − α)nF(E − Erev)
RT
[4]
Where I is the current, Ilim is the limiting current, Iex is the exchange
current density, CO and CR are the concentration of the oxidized and
reduced species at the surface of the electrode, CO* and CR* are
the bulk concentrations of the oxidized and reduced species, α is the
transfer coefficient, n is the number of electrons transferred, F is the
Faraday constant, E-Erev is the overpotential, R is the gas constant,
and T is the temperature.
The rate constant, ko, was obtained from the exchange current
density (Eq. 5).
ko = Iex /nF AC∗
[5]
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Figure 2. Cyclic voltammograms at a scan rate of 5 mV s−1 on a glassy carbon electrode in 1 M sulfuric acid containing (a)1 mM anthraquinone-2-sulfonic acid,
(b)1 mM anthraquinone-2,6-disulfonic acid and (c)1 mM 1,2-benzoquinone-3,5-disulfonic acid.
Besides BQDS, AQS and AQDS, we have also measured the
current-overpotential curves for hydroquinone and hydroquinone sul-
fonic acid (see supplementary material). Solubility of anthraquinone
in 1 M sulfuric acid was too low to obtain any reliable data.
The half-wave potential values (Table I) are consistent with the
values reported in the literature for the various compounds tested.29,31
It is clear that the addition of aromatic rings has a marked effect
of lowering the standard reduction potential and half-wave potential.
The addition of sulfonic acid groups tends to increase the standard
reduction potential, which is consistent with the lowering of molecular
orbital energies by electro-withdrawing groups.
To understand the changes in the standard reduction potentials we
have used quantum mechanics to calculate the free-energy change in
the reaction of the oxidized form of the redox couple with hydrogen. If
Go
is the Gibbs free energy change under standard conditions, then
− Go
/nF is the standard electrode potential for the redox couple,
Table I. Standard reduction potentials for selected quinones.
Standard Reduction Potentials
Redox Couple Experimental (E1/2 values) vs. NHE Eo(formal) Theoretical
Hydroquinone 0.67 0.68 0.70
Hydroquinone sulfonic acid 0.82 0.70 0.77
1,2-benzoquinone -3,5-disulfonic acid 1.1 0.87 0.85
Anthraquinone Insoluble Insoluble 0.05
Anthraquinone-2-sulfonic acid 0.13 0.15 0.09
Anthraquinone-2,6-sulfonic acid 0.05 0.19 0.12
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Figure 3. Linear sweep voltammetric data (scan rate of 5 mV s−1) at a glassy carbon rotating disk electrode for 1 mM concentration of BQDS (a), AQS (b) and
AQDS (c) at the rotation rates indicated. Electrode potentials are versus a mercury sulfate reference electrode (E0 = +0.65). (d) Levich plot of the square root of
rotation rate vs the limiting current for AQS(♦), BQDS ( ), and AQDS (o). (e) Mass transport-corrected current-voltage plot for BQDS, AQS, and AQDS.
where n is the number of protons involved in the reaction and the F
is the Faraday constant. The values of E1/2 from experiments follow
the trends predicted by the theoretical calculations (Table I). The
strong correlation between experimental and theoretical predictions
suggest that such free energy calculations can be used to predict the
trends in E1/2 values of the redox compounds prior to experimental
testing, potentially enabling the discovery of new redox couples by
this computational approach.
The values of diffusion coefficients (Table II) are about an or-
der of magnitude smaller in aqueous solutions than in non-aqueous
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Table II. Electrochemical properties of the redox couples determined from rotating disk electrode experiments. MSE refers to the mercury sulfate
reference electrode (Eo = +0.65 V).
Exchange Diffusion Transfer
E1/2 vs. MSE, Current Density, Coefficient, Coefficient, Constant,
Redox Couple (Volt) (A cm−2) (cm2 s−1) αn Solubility (cm s−1)
Hydroquinone 0.02 5.09E-5 5.03E-6 0.508 0.53 M 2.36E-3
Hydroquinone sulfonic acid 0.17 1.10E-5 4.28E-6 0.418 0.8 M 5.52E-4
1,2-benzoquinone -3,5-disulfonic acid 0.45 3.00E-6 3.80E-6 0.582 1 M 1.55E-4
Anthraquinone-2- sulfonic acid −0.52 1.96E-5 3.71E-6 0.677 0.2 M 2.25E-4
Anthraquinone 2,6-disulfonic acid −0.60 2.97E-6 3.40E-6 0.426 0.5 M 1.52E-4
solvents such as acetonitrile.32
In aqueous solutions, the observed ex-
tent of decrease in the values of diffusion coefficients with increase in
molecular mass is about 6 × 10−9
cm2
s−1
per unit of molecular mass.
This coefficient is an order of magnitude lower than that observed in
acetonitrile. Thus, besides the effect of molecular mass, the molecu-
lar diameters resulting from the solvation and the interaction of ionic
groups with water through hydrogen bonding have a significant effect
on the diffusion coefficient values in aqueous solutions.
Rate constants are within the range of values found widely in
the literature for quinones.33,34
As sulfonic acid groups are added to
the ring, the intra-molecular hydrogen bonding interactions in the
quinone molecules increase. This intra-molecular hydrogen bonding
plays a critical role in the rate limiting step of proton-coupled electron
transfer,35
due to the increased stability of the compound and increased
cleavage energy required for concerted proton and electron transfer.
This stability provides a competition between the resident hydro-
gen atom and the incoming proton for interaction with the carbonyl
oxygen. According to our calculations, hydroquinone sulfonic acid
preferentially adopts a conformation allowing the formation of intra-
molecular hydrogen bonding, which leads to a stabilization energy of
1.6 kcal mol−1
. Similarly, intra-molecular hydrogen bonding provides
extra stabilization of other hydroquinone sulfonic acid derivatives
(Eq. 6 and Eq. 7). Thus, the intra-molecular hydrogen bonding could
explain the lowering of the rate constants observed with the addition
of sulfonic acid groups.
[6]
[7]
The quinone-based redox systems have been extensively reported
in the literature36–38
and it is well known that these systems undergo
proton-coupled electron transfer. The rate constants for charge transfer
were generally quite high, at least an order of magnitude higher than
that observed for the vanadium redox couples.17
The value of the
transfer coefficients being close to 0.5 and the high values of rate
constants suggest an “outer-sphere” process.
While the rate constants for the various compounds were at least
one order of magnitude greater than that of vanadium system, the dif-
fusion coefficients were comparable to that of vanadium,18
making the
quinone redox couples very attractive from the standpoint of electrode
kinetics compared to the vanadium redox flow battery system.
The Nernst diffusion layer model allows us to estimate the limiting
current for the oxidation and reduction processes (Eq. 8).
Ilim = nFC∗ D
δ
[8]
Where Ilim is the limiting current density, n is the number of moles
of electrons transferred per mole of reactants, F is the Faraday con-
stant (96485 C mole−1
), C* is the concentration, DO is the diffusion
coefficient, and δ is the diffusion layer thickness.
For a diffusion layer thickness of 50 microns, a diffusion coeffi-
cient of 3.8 × 10−6
cm2
s−1
, and a bulk concentration of 0.2 M, we
predict from Eq. 8 a limiting current density at room temperature to
be approximately 30 mA cm−2
. Further increase in limiting current
density can be achieved by increasing the concentration of reactants,
reducing the diffusion layer thickness, and by increasing the diffu-
sion coefficient. Higher concentrations and diffusion coefficients are
achieved by raising the operating temperature while a lower diffu-
sion layer thickness can be achieved by increased convective mass
transport to the surface of the electrode.
We have operated flow cells with aqueous solutions of 0.2 M BQDS
at the positive electrode and 0.2 M AQS or 0.2M AQDS at the negative
electrode. In these cells the electrodes consisted of Toray paper coated
with high-surface area carbon black bonded to the Nafion membrane.
These cells did not show any noticeable change in capacity over at
least 12 cycles of repeated charge and discharge (Figure 4). This result
confirmed that the quinones in aqueous acid solution are chemically
stable to repeated cycling. The capacity realized at a current density of
10 mA cm−2
was over 90% of the capacity contained in the solutions.
The use of Toray paper electrodes on either side of the cell as current
collecting surfaces presented a barrier to convective transport, setting
the diffusion layer thickness to as high as 150 microns, reducing the
limiting current density and lowering the cell voltage.
Increasing the mass transport of reactants and products improved
the current density and cell voltage significantly. In one configuration
of the electrodes, the increase in mass transport was achieved by
punching nine equally-spaced holes 1 cm in diameter in the Toray
paper electrodes to allow the flow of redox active materials to shear
directly past the carbon black layer bonded to the membrane. The
increased current and voltage observed as a result of the change in the
access of the redox materials to the electrode (Figure 5) confirmed
that the kinetics of the electrode reactions are largely controlled by
the mass transport of the reactants and products.
The dependency of cell voltage on current density when measured
as a function of the state of charge of ORBAT confirmed that the mass
transport of reactants had a significant impact on the operating cell
voltage (Figure 6a). The power density of the cell decreased signifi-
cantly below 50% state-of-charge. The alternating current impedance
of the cells measured as a function of frequency also confirmed that
the mass transport limitations increased as the state-of-charge de-
creased. The slopes of the Nyquist plot at low frequencies (< 1 Hz)
were found to steadily increase with decreasing state-of-charge, while
the rest of the impedance spectrum remained almost unaffected
(Figure 6b), suggesting an increasing thickness of the diffusion lay-
ers with a decrease in the state-of-charge. Therefore, it is clear from
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Figure 4. 12 charge and discharge curves with a 25 cm2
redox flow cell, 0.2 M BQDS and 0.2 M AQS, 1 M
sulfuric acid, charge and discharge at 200 mA, flow rate
of 0.5 liters min−1.
Figure 5. The effect of electrode structure on cell per-
formance: 9 equally spaced holes 1 cm in diameter were
punched in the Toray paper electrodes. 25 cm2 redox
flow cell, 0.2 M BQDS, 0.2 M AQS, 1 M sulfuric acid,
charge-discharge at 50 mA, flow rate 0.25 liter min−1
the results in Figure 6 that at all current densities, mass transport
limitations made a significant contribution to the overpotential losses.
In an effort to understand the results presented in Figure 6, we have
analysed the effect of state-of-charge on the current-voltage character-
istics using a simplified one-dimensional model (see Appendix). The
assumptions in this analysis are based on experimental findings from
RDE studies and flow cell studies that show that the charge-transfer
reactions are facile and that mass transport processes determine the
cell voltage during operation.
The analysis yields the following relationship between the ob-
served cell voltage and the discharge current as a function of state-of-
charge.
Vcell = E0
c −E0
a
RT
nF
ln
Q2
(1−Q)2
−2Id
RT
nF
1
nFmt AQCi −Id
+
1
nFmt A(1 − Q)Ci + Id
− Id Rohmcell [9]
Where Vcell is the cell voltage during discharge and Ecnot and Eanot
are the standard reduction potentials for the two redox couples used
at the cathode and anode, respectively. Id is the discharge current
and Q is the state-of-charge with values between 0 to 1. Cinitial is the
starting concentration of the reactants at 100% state-of-charge; Cinitial
is assumed in this analysis to be the same at both electrodes. A is the
area of the electrode, and mt is the mass transport coefficient defined
as the diffusion coefficient divided by the diffusion layer thickness.
R is the universal gas constant, F is the Faraday constant, T is the
temperature, and n is the number of electrons in the redox reaction.
Eq. 9 has been graphed (Figure 7) for various states-of-charge using
experimentally determined parameters for the BQDS and AQS system
(Table III). Comparison of Figure 7 with the experimental data in Fig-
ure 6 shows general agreement of the trend predicted by the analysis
with the observed experimental results; decrease in state-of-charge
resulted in a decrease of discharge current at any particular voltage,
leading to a significant reduction in discharge rate capability at low
states-of-charge. However, the experimental current-voltage curves
were nearly linear at the high states of charge and the experimental
values of cell voltage at low current values decreased substantially
with decreasing state-of-charge. These deviations from the analytical
expression suggest that there are additional resistance elements under
dynamic operating conditions that are not captured in the simplified
analysis. We list at least two other effects that can cause substantial
changes to the observed voltage:
1. Electro-osmotic drag of water molecules (estimated to be about 3
molecules per proton) occurs across the membrane during passage
of current. These water molecules either appear at or are removed
from the diffusion layer at each electrode causing changes to the
pH and concentration of reactants and products. These concen-
tration changes at the interface will contribute to a reduction in
cell voltage. For example, at the cathode during discharge, wa-
ter molecules could be added to the diffusion layer causing the
pH to increase and, consequently, the electrode potential to de-
crease. Correspondingly, water molecules will be removed from
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Figure 6. 25 cm2 redox flow cell, 0.2 M BQDS, 0.2 M AQS, 1 M sulfuric
acid (a) Cell voltage-current density curves as a function of state-of-charge
(5% difference each run). (b) Impedance spectroscopy data from 10 kHz to
10 mHz on the cells at various states-of-charge.
Table III. Parameters used in the analysis of current-voltage
curves as a function of state-of-charge.
Parameter Value
Standard Reduction Potential of Cathode (Ecnot), V +0.45
Standard Reduction Potential of Anode (Eanot), V −0.52
Initial concentration of reactants (Cinitial) moles cm−3 2 E-4
Diffusion coefficient of cathode and anode reactants
and products (D) cm2 s−1
4E-6
Diffusion layer thickness (δ) cm 4E-3
Geometric Area of the Electrode (A), cm2 25
Number of electrons in the reaction (n) 2
Series equivalent resistance at impedance at 10 kHz
(Rohmcell), Ohm
0.05
the anode, causing the pH to decrease, the electrode potential to
increase, and the cell voltage to decrease.
2. At the anode, we use a solution of AQS at concentrations close
to the solubility limit (0.2 M). Consequently, at a low state-of-
charge when the oxidized form of AQS at the negative electrode
is present in high concentrations in the bulk of the solution, the
high rates of discharge would cause the solubility limits to be
exceeded at the surface of the negative electrode. This would
result in the precipitation of redox materials at the surface of the
electrode and with a significant reduction of the current. To avoid
such an abrupt drop in cell voltage at high current densities and
low states-of-charge, the solubility of the redox materials must be
high. Additionally, reducing the thickness of the diffusion layer
by using a flow-through electrode will increase the “saturation-
limited” current density.
The analysis helps us to quantify the variations in performance
that can result from changes to local mass-transport conditions at any
state-of-charge. The observed differences between the experimental
data and the predictions of simple analysis of the cell performance
also help us to identify the phenomena that are important to consider
for further design and modeling of redox flow cells.
When an aqueous solution of 0.2 M AQDS was used on the negative
side of the flow battery, the tests showed charge-discharge cycling
Figure 7. Simulation of cell voltage as a func-
tion of discharge current density (as per Eq. A5)
at various states-of-charge, as indicated on the
curves using parameters in Table III.
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Figure 8. a) 12 charge and discharge curves with a 25 cm2 redox flow cell,
0.2 M BQDS, 0.2 M AQDS, 1 M sulfuric acid, charge and discharge at
200 mA, flow rate of 1 liters min−1 on a peristaltic pump. b) Cell voltage-
current density curves as a function of state-of-charge (as indicated by percent
stated, 5% difference each run) in a 25 cm2 redox flow cell, 0.2 M BQDS,
0.2 M AQDS, 1 M sulfuric acid.
stability similar to AQS. By operating at a higher pumping speed,
the cell voltages and capacity for the BQDS/AQDS cell could be
increased, consistent with the reduction of the voltage losses from
mass transport limitations (Figure 8a). The cell voltage and current
density did not drop off as quickly with state-of-charge as in the case
of AQS. The aqueous solubility limit of AQDS is about 0.5 M while
that of AQS is about 0.2 M. Consequently, even at very low states-of-
charge, the solubility limit was less likely to be exceeded with AQDS
than with AQS. Thus, higher solubility allows the cell voltage to be
maintained at a higher value with AQDS compared to AQS especially
at low states-of-charge. This difference in performance of AQDS and
AQS highlights the role of solubility limits on the rate capability
at various states-of-charge. Such findings motivate us to investigate
higher concentrations and temperatures with AQDS in future studies.
Conclusions
For the first time, we have demonstrated the feasibility of operating
an aqueous redox flow cell with reversible water-soluble organic redox
couples (we have termed ORBAT). This type of metal-free flow bat-
tery opens up a new area of research for realizing inexpensive and ro-
bust electrochemical systems for large-scale energy storage. The cells
were successfully operated with 1,2-benzoquinone disulfonic acid at
the cathode and anthraquinone-2-sulfonic acid or anthraquinone-2,6-
disulfonic acid at the anode. The cell used a membrane-electrode
assembly configuration similar to that used in the direct methanol
fuel cell.39
We have shown that no precious metal catalyst is needed
because these redox couples undergo fast proton-coupled electron
transfer.
We have determined the critical electrochemical parameters and
various other factors governing the performance of the cells. The stan-
dard reduction potentials calculated using density functional theory
were consistent with the experimentally determined values. This type
of agreement suggested that quantum mechanical methods for predic-
tion of the reduction potentials could be used reliably for screening
various redox compounds. The experimental values of the diffusion
coefficients of the various quinones in aqueous sulfuric acid sug-
gested that strong interaction of the ionized quinones with water
resulted in lower diffusion coefficients compared to those in non-
aqueous media. Further, we found that significant stabilization by
intra-molecular hydrogen bonding occurred with the sulfonic acid
substituted molecules. These differences will be important to con-
sider in interpreting the changes in the rate of proton-coupled electron
transfer in these molecules.
Our experiments also demonstrated that the organic redox flow
cells could be charged and discharged multiple times at high faradaic
efficiency without any sign of degradation. Our analysis of cell per-
formance shows that the mass transport of reactants and products and
their solubilities are critical to achieving high current densities.
Further testing and analysis is underway to understand the behavior
of other redox couples in the quinone family, assess the impact of
solubility on full cell performance, and optimize the structure of the
membrane-electrode assemblies. Solubility is still a challenge for this
type of redox flow battery. Choosing a substituent such as sulfonic
acid to modify both positive and negative electrode materials appears
to be the most promising approach at this time to meet the challenge of
solubility in water. However, understanding the effect of substituent
group type and placement on the standard reduction potential and
kinetic reversibility are also important areas for further study.
Acknowledgment
We acknowledge the financial support for this research from
ARPA-E Open-FOA program (DE-AR0000337), the University of
Southern California, and the Loker Hydrocarbon Research Insti-
tute. Both authors Bo Yang and Lena Hoober-Burkhardt contributed
equally to this work.
Appendix
Analysis of Current-voltage Curves at Various States of Charge
The following analysis is aimed at deriving a relationship between cell voltage and
discharge current for a flow battery using electrochemically reversible redox couples. For
any cell undergoing disharge, the cell voltage and current are related by Eq. A1.
Vcell = Ec − Ea − Idisch Rohm [A1]
Where Vcell is the cell voltage, Ec is the electrode potential of the cathode, Ea is the
electrode potential of the anode, I is the discharge current, and Rohm is the series equivalent
resistance of the electrolyte and current collectors.
For electrodes with reactions involving with rapid charge transfer kinetics relative to
mass transport processes (usually termed as kinetically reversible reactions), the electrode
potentials are given by the Nernst equation.
Ec = Eo
c + (RT/nF) ln (Co,c/Cr,c) [A2]
Ea = Eo
a + (RT/nF)ln(Co,a/Cr,a) [A3]
In Eqs. A2 and A3, and in subsequent equations, the subscripts c and a refer to the cathode
and anode, respectively. Co and Cr are the concentrations of the oxidized and reduced
species at the surface of the electrode.
Let Co,c*, Cr,c*, Co,a*, Cr,a* be the concentration of the species in the bulk of the
solution at the respective electrodes, and the asterisk will always refer to the values in
the bulk of the solution.When the flow rate is high relative to the consumption rate at the
electrodes, we expect the concentrations to be uniform in the plane of the electrode. Under
these conditions, we may describe the variation in concentration due to mass transport
limitations only in one-dimension, i.e., perpendicular to the surface of the electrode.
In the steady-state, the discharge current Idisch, can be related to the diffusion coeffi-
cient, D, concentration of reactants and products, and the diffusion layer thickness, δ by
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Fick’s first law.
Idisch = nF AD(C∗
o,c − Co,c)/δ = nF Amt (C∗
o,c − Co,c) [A4]
Idisch = nF AD(Cr,c − C∗
r,c)/δ = nF Amt (Cr,c − C∗)
r,c [A5]
We also define the mass transfer coefficient, mt, as is equal to D/δ for the oxidized and
reduced species. The values of mt for the cathode and anode will be assumed to be same
in the analysis because we are considering a case of symmetrical electrode structures and
same flow rates, and molecules with very similar diffusion coefficients. A is the area of
the electrode.
Re-arranging Eqs. A4 and A5 we obtain,
Co,c = C∗
o,c − Idisch /nF Amt ; Cr,c = Idisch /nF Amt + C∗
r,c [A6]
Similarly, at the anode, the discharge current and surface concentration are given by,
Co,c = Idisch /nF Amt + C∗
o,c; Cr,a = C∗
r,c − Idisch /nF Amt [A7]
The change in concentration resulting from changes at the anode and cathode is given by
dCo,c = −dIdisch /nF Amt [A8a]
dCr,c = dIdisch /nF Amt [A8b]
dCo,c = −dIdisch /nF Amt [A9a]
dCr,a = −dIdisch /nF Amt [A9b]
From the Nernst equation, we can obtain the change in potential resulting from such
changes in concentration.
dEc = (RT/nF){(1/Co,c)dCo,c − (1/Cr,c)dCr,c} [A10a]
dEa = (RT/nF){(1/Co,a)dCo,a − (1/Cr,a)dCr,a } [A10b]
From Eqs. A8, A9 and A10 we obtain,
d(Ec − Ea) = −(RT/n2
F2
Amt )(1/Co,c + 1/Cr,c + 1/Co,a + 1/Cr,a)dIdisch [A11]
Let Cinitial be the concentration in both reservoirs of equal volume at the start of the
experiment. Then, even at various states of charge, the sum of the bulk concentrations of
the oxidized and reduced species on both sides will equal Cinitial.
Cinitial = Co∗
+ Cr∗
[A12]
Since Cinitial can now be used to define the state-of-charge, Q, as follows.
C∗
o,c = QCinitial [A13]
C∗
r,c = (1 − Q)Cinitial [A14]
For the anode,
C∗
r,a = QCinitial [A15]
C∗
o,a = (1 − Q)Cinitial [A16]
Combining Eqs. A6, A7, A11, and A12–A15, we obtain
d(Ec − Ea)/dIdisch = −2(RT/nF){(1/(nF Amt QCinitial − Idisch )
+1/(nF Amt (1 − Q)Cinitial + Idisch )
At any state of charge, the electrode potential is related to the state of charge by:
Ec,eq = Ecnot + RT/nF ln Q/(1 − Q) [A17]
Ea,eq = Eanot + RT/nF ln(1 − Q)/Q [A18]
The cell voltage in Eq. A1 can then be expressed as,
Vcell = Ec,eq − Ea,eq − Idisch {d(Ec − Ea)/dIdisch } − IRohmcell [A19]
Substituting for the various terms in Eq. A19 from above, we have an expression for
the cell voltage as a function of discharge current and state of charge, when the initial
concentration of the active materials are the same on both sides.
Vcell = Ecnot − Eanot + (RT/nF) ln Q2
/(1 − Q)2
− 2Idisch (RT/nF)[(1/(nFmt AQCinitial − Idisch )
+ 1/(nFmt A(1 − Q)Cinitial + Idisch )] − Idisch Rohmcell [A20]
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