This document reviews recent progress in nitrogen-doped graphene. It discusses various synthesis methods for nitrogen-doped graphene including chemical vapor deposition, segregation growth, solvothermal synthesis, and arc discharge. It describes common nitrogen bonding configurations in nitrogen-doped graphene of pyridinic nitrogen, pyrrolic nitrogen, and graphitic nitrogen. The document also reviews potential applications of nitrogen-doped graphene in areas like electrocatalysis, field-effect transistors, and energy storage based on experimental and theoretical studies.
Review on recent progress in nitrogen doped graphene synthesis, characterizat...suresh899
This document reviews recent progress in nitrogen-doped graphene, including various synthesis methods and characterization techniques. Some key points:
1. Nitrogen doping introduces pyridinic, pyrrolic, and graphitic nitrogen configurations in graphene which alter its electronic properties.
2. Synthesis methods include CVD, segregation growth, solvothermal, arc discharge, and post-treatment methods like thermal, plasma, and N2H4 treatments.
3. CVD is a common method using metal catalysts and carbon/nitrogen precursors. Other methods include solvothermal reactions and arc discharge of graphite sources.
Review on recent progress in nitrogen doped graphene synthesis, characterizat...materials87
Nitrogen doping has been an effective way to
tailor the properties of graphene and render its potential use
for various applications. Three common bonding configurations
are normally obtained when doping nitrogen into the
graphene: pyridinic N, pyrrolic N, and graphitic N. This paper
reviews nitrogen-doped graphene, including various synthesis
methods to introduce N doping and various characterization
techniques for the examination of various N bonding
configurations. Potential applications of N-graphene are also
reviewed on the basis of experimental and theoretical studies
A review on recent progress in nitrogen doped graphene synthesis, characteriz...Science Padayatchi
1) Nitrogen doping is an effective way to modify the properties of graphene. There are three common types of nitrogen dopants: pyridinic N, pyrrolic N, and graphitic N.
2) Many methods have been used to synthesize nitrogen-doped graphene (N-graphene), including CVD, segregation growth, solvothermal synthesis, and arc discharge. Post-treatment methods include thermal treatment, plasma treatment, and treatment with N2H4.
3) The nitrogen content and dopant configuration in N-graphene can be controlled by parameters like precursor composition, catalyst material, and growth temperature. N-graphene has potential applications in areas like electrocatalysis
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized
using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized
catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without
using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized
using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized
catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without
using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
The document summarizes a study on using palladium supported on hydrotalcite as a heterogeneous catalyst for the Suzuki cross-coupling reaction. Various palladium salts were tested as catalysts with different bases and temperatures. PdCl2 supported on hydrotalcite with potassium carbonate as the base provided the best results, with conversions comparable to homogeneous catalysts at temperatures above 90°C. The catalyst was characterized and found to have a palladium content of 1% without changing the structure of the hydrotalcite support. It was an effective catalyst for the reaction, with higher temperatures, bromobenzene, and chlorobenzene providing better conversions than other conditions tested.
Carbon Nitride Grafted Cobalt Complex (Co@npg-C3N4) for Visible LightAssiste...Pawan Kumar
1) A cobalt complex was covalently grafted to nanoporous graphitic carbon nitride (npg-C3N4) via a click reaction to create a heterogeneous photocatalyst called Co@npg-C3N4.
2) Under visible light irradiation at room temperature, Co@npg-C3N4 efficiently catalyzed the direct esterification of aldehydes without the need for an external base.
3) Characterization of Co@npg-C3N4 showed the cobalt complex was successfully immobilized via click chemistry, providing a robust photocatalyst that could be easily recovered and reused without significant loss of activity.
Review on recent progress in nitrogen doped graphene synthesis, characterizat...suresh899
This document reviews recent progress in nitrogen-doped graphene, including various synthesis methods and characterization techniques. Some key points:
1. Nitrogen doping introduces pyridinic, pyrrolic, and graphitic nitrogen configurations in graphene which alter its electronic properties.
2. Synthesis methods include CVD, segregation growth, solvothermal, arc discharge, and post-treatment methods like thermal, plasma, and N2H4 treatments.
3. CVD is a common method using metal catalysts and carbon/nitrogen precursors. Other methods include solvothermal reactions and arc discharge of graphite sources.
Review on recent progress in nitrogen doped graphene synthesis, characterizat...materials87
Nitrogen doping has been an effective way to
tailor the properties of graphene and render its potential use
for various applications. Three common bonding configurations
are normally obtained when doping nitrogen into the
graphene: pyridinic N, pyrrolic N, and graphitic N. This paper
reviews nitrogen-doped graphene, including various synthesis
methods to introduce N doping and various characterization
techniques for the examination of various N bonding
configurations. Potential applications of N-graphene are also
reviewed on the basis of experimental and theoretical studies
A review on recent progress in nitrogen doped graphene synthesis, characteriz...Science Padayatchi
1) Nitrogen doping is an effective way to modify the properties of graphene. There are three common types of nitrogen dopants: pyridinic N, pyrrolic N, and graphitic N.
2) Many methods have been used to synthesize nitrogen-doped graphene (N-graphene), including CVD, segregation growth, solvothermal synthesis, and arc discharge. Post-treatment methods include thermal treatment, plasma treatment, and treatment with N2H4.
3) The nitrogen content and dopant configuration in N-graphene can be controlled by parameters like precursor composition, catalyst material, and growth temperature. N-graphene has potential applications in areas like electrocatalysis
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized
using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized
catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without
using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized
using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized
catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without
using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
The document summarizes a study on using palladium supported on hydrotalcite as a heterogeneous catalyst for the Suzuki cross-coupling reaction. Various palladium salts were tested as catalysts with different bases and temperatures. PdCl2 supported on hydrotalcite with potassium carbonate as the base provided the best results, with conversions comparable to homogeneous catalysts at temperatures above 90°C. The catalyst was characterized and found to have a palladium content of 1% without changing the structure of the hydrotalcite support. It was an effective catalyst for the reaction, with higher temperatures, bromobenzene, and chlorobenzene providing better conversions than other conditions tested.
Carbon Nitride Grafted Cobalt Complex (Co@npg-C3N4) for Visible LightAssiste...Pawan Kumar
1) A cobalt complex was covalently grafted to nanoporous graphitic carbon nitride (npg-C3N4) via a click reaction to create a heterogeneous photocatalyst called Co@npg-C3N4.
2) Under visible light irradiation at room temperature, Co@npg-C3N4 efficiently catalyzed the direct esterification of aldehydes without the need for an external base.
3) Characterization of Co@npg-C3N4 showed the cobalt complex was successfully immobilized via click chemistry, providing a robust photocatalyst that could be easily recovered and reused without significant loss of activity.
The document summarizes the synthesis and characterization of plumbum(II) complexes with mixed ligands of bis(N-alkyl-N-ethyldithiocarbamates) and 1,10-phenanthroline. Specifically, it describes the synthesis of new plumbum(II) complexes with butyl and cyclohexyl dithiocarbamate ligands and their adducts with phenanthroline. Elemental analysis, infrared spectroscopy, and 13C NMR spectroscopy were used to characterize the complexes and confirmed the proposed structures.
This document is a chapter from a general chemistry textbook titled "General Chemistry: Principles and Modern Applications" by Petrucci, Harwood, and Herring. The chapter is titled "Liquids, Solids and Intermolecular Forces" and covers topics such as the properties of liquids and solids, intermolecular forces like hydrogen bonding and van der Waals forces, phase diagrams, crystal structures of solids, and energy changes during phase changes. It includes diagrams to illustrate concepts like vapor pressure curves, phase diagrams, and crystal unit cells.
1) Atmospheric CO2 levels have risen from 280 ppm pre-industrially to over 410 ppm currently due to emissions from fossil fuel combustion and respiration. Maximum safe levels are believed to be 450 ppm or less to avoid worst effects of global warming and ocean acidification.
2) The document discusses strategies for converting CO2 into useful products like dimethyl carbonate (DMC), formic acid and methanol. It outlines more sustainable routes for producing these chemicals directly from CO2 rather than traditional methods that rely on other carbon sources.
3) Specifically, it presents a method for continuously producing pure formic acid by hydrogenating supercritical CO2 with an immobilized catalyst and base, avoiding high
This document is a chapter from a general chemistry textbook. It is chapter 6, which covers gases. The chapter contains 9 sections that discuss gas properties and laws, including gas pressure, the simple gas laws, the ideal gas equation, applications of the ideal gas equation like determining molar mass, gases in chemical reactions, mixtures of gases, kinetic molecular theory, gas properties related to kinetic molecular theory, and non-ideal gases. The chapter also includes sample problems and questions at the end.
This chapter of the general chemistry textbook discusses solubility and complex ion equilibria. It covers topics such as the solubility product constant Ksp, the common ion effect, limitations of Ksp, criteria for precipitation, fractional precipitation, effects of pH on solubility, and equilibria involving complex ions. It also describes the process of qualitative cation analysis using selective precipitation of cations in different solubility groups.
Density functional theory calculations were performed to investigate the structural, electronic, and CO2 adsorption properties of 55-atom bimetallic CuNi nanoparticles. The calculations revealed that decorated Cu12Ni43 and core-shell Cu42Ni13 configurations were more energetically favorable than the monometallic Cu55 and Ni55 nanoparticles. CO2 was found to chemisorb on Ni55, Cu13Ni42, Cu12Ni43, and Cu43Ni12 by undergoing a transition from linear to bent geometry and elongating the C=O bonds, while it only physisorbed on Cu55 and Cu42Ni13. The presence of surface Ni atoms played a key role in strongly adsorbing and activating CO
Maiyalagan,Performance of carbon nanofiber supported pd ni catalysts for elec...kutty79
Carbon nanofibers (CNF) supported Pd–Ni nanoparticles have been prepared by chemical reduction
with NaBH4 as a reducing agent. The Pd–Ni/CNF catalysts were characterized by X-ray diffraction
(XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical
voltammetry analysis. TEM showed that the Pd–Ni particles were quite uniformly distributed on the
surface of the carbon nanofiber with an average particle size of 4.0 nm. The electro-catalytic activity of
the Pd–Ni/CNF for oxidation of ethanol was examined by cyclic voltammetry (CV). The onset potential
was 200mV lower and the peak current density four times higher for ethanol oxidation for Pd–Ni/CNF
compared to that for Pd/C. The effect of an increase in temperature from 20 to 60 ◦C had a great effect on
increasing the ethanol oxidation activity
The peer-reviewed International Journal of Engineering Inventions (IJEI) is started with a mission to encourage contribution to research in Science and Technology. Encourage and motivate researchers in challenging areas of Sciences and Technology.
This document describes a computational fluid dynamics (CFD) study of methane decomposition into hydrogen and solid carbon in a packed bed fluid catalytic cracking (FCC) reactor. The study used CFD modeling in COMSOL Multiphysics to simulate the decomposition reaction over time in the packed bed reactor. Results showed that increasing the reaction time from 0 to 1000 seconds increased the production of hydrogen from 0 to 42 mol/dm3 and carbon from 0 to 21 mol/dm3, while decreasing methane concentration from 50 to 29 mol/dm3, indicating that decomposition was occurring. Spatial profiles of velocity, concentration, pressure and permeability within the reactor were also determined and discussed.
Deposition of ni ti n coatings by a plasma assisted mocvd using an organometa...tshankar20134
Titanium nitride (TiN)/nickel (Ni) composite coatings were synthesized by plasma assisted metal-organic
chemical vapour deposition (PAMOCVD) using organo-metallic and metal-organic complexes namely dichlorobis(5-
cyclopentadienyl)titanium (IV) for titanium and N,N'-ethylene-bis(2,4-pentanedion-iminoato)nickel(II) for nickel. The
growth of such films was investigated in nitrogen (N2) plasma environment in the substrate temperature range of 450-
550ºC at a deposition pressure of 0.5-1 mbar. Prior to the deposition of films, the Ti precursor was subjected to the
equilibrium vapour pressure measurements by employing TG/DTA in transpiration mode, which led to the value of 109.2
± 5.6 kJ mol-1 for the standard enthalpy of sublimation (Ho
sub). The phase identification using glancing incidence x-ray
diffraction showed Ni/TiN is a nanocomposite coating containing nanocrystals of Ni and TiN with face centered cubic
structure. Scanning electron microscopy revealed a uniform surface morphology of the films, while chemical analysis by
energy dispersive analysis confirmed the presence of titanium, nickel and nitrogen in the composite films.
Nanostructured fe2 o3 platform for the electrochemical sensing of folic acidtshankar20134
The document describes the synthesis of alpha-iron oxide (α-Fe2O3) nanofibers using a simple electrospinning method and their application for the electrochemical sensing of folic acid (FA). The α-Fe2O3 nanofiber-modified glassy carbon electrode showed good selectivity for detecting FA even in the presence of ascorbic acid, achieving a detection limit of 60 nM for FA. The α-Fe2O3 nanofibers provided a high surface area platform and enhanced the oxidation current and separation of voltammetric signals for FA and ascorbic acid compared to an unmodified electrode. The modified electrode was successfully used to determine FA concentrations in human blood serum samples.
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.
Electro catalytic performance of pt-supported poly (o-phenylenediamine) micro...tshankar20134
This document summarizes research on developing a nanocomposite catalyst of Pt supported on poly(o-phenylenediamine) (PoPD) microrods for electro-oxidation of methanol in fuel cells. PoPD microrods were synthesized through an interfacial polymerization method using ferric chloride. Pt nanoparticles were deposited on the PoPD microrods using sodium borohydride reduction of chloroplatinic acid. Characterization with XRD showed the Pt had a face-centered cubic structure. Electrochemical tests found the Pt/PoPD catalyst had higher catalytic activity and stability for methanol oxidation compared to a Pt/carbon catalyst, which may be due to the microrod morphology facilitating better
Template synthesis and characterization of well aligned nitrogen containing c...tshankar20134
This document describes the synthesis and characterization of nitrogen-containing carbon nanotubes produced through the pyrolysis of polyvinyl pyrrolidone on an alumina membrane template. The nanotubes were analyzed using various techniques which showed they had a hollow, vertically aligned structure with a significant amount of nitrogen incorporated into the carbon framework, as evidenced by elemental analysis, Raman spectroscopy, IR spectroscopy, and XPS. The template synthesis method allowed production of well-aligned nitrogen-containing carbon nanotubes with controlled morphology and composition.
One pot synthesis of chain-like palladium nanocubes and their enhanced electr...tshankar20134
This document describes a one-pot synthesis of chain-like palladium nanocubes and their enhanced electrocatalytic activity. A simple aqueous approach is used to produce anisotropic cubic chain-like Pd nanostructures using the neurotransmitter 5-hydroxytryptamine. Scanning electron microscopy images show the nanocubes have sizes between 140-210 nm and form chain-like branched structures. Testing shows the cubic chain-like nanostructures have over 11 times greater electrocatalytic activity for oxidizing formic acid, methanol, and ethanol compared to spherical nanoparticles and commercial Pd/C catalysts. The enhanced performance makes them promising multipurpose catalysts for direct fuel cells.
Highly stable pt–ru nanoparticles supported on three dimensional cubic ordere...tshankar20134
This document describes the synthesis and characterization of Pt-Ru nanoparticles supported on cubic ordered mesoporous carbon (Pt-Ru/CMK-8) and their evaluation as electrocatalysts for methanol oxidation in direct methanol fuel cells. Two types of CMK-8 carbon with different pore sizes were synthesized using two different mesoporous silica templates. Pt-Ru was deposited on the CMK-8 using sodium borohydride reduction. Characterization showed the CMK-8 had high surface areas over 1000 m2/g and pore volumes over 1.26 cm3/g. Electrochemical testing found the Pt-Ru/CMK-8-I catalyst had a high specific mass activity of 487
V mn-mcm-41 catalyst for the vapor phase oxidation of o-xylenetshankar20134
This document summarizes research on V-Mn-MCM-41 catalysts for the vapor phase oxidation of o-xylene. Mesoporous monometallic and bimetallic catalysts with varying ratios of vanadium and manganese were synthesized and characterized. Their activity for oxidizing o-xylene to phthalic anhydride was measured and found to correlate with their physical and chemical properties. The V-MCM-41 catalyst with a Si/V ratio of 50 exhibited the highest activity and selectivity. Vanadium species in the +5 oxidation state within the MCM-41 silica matrix were determined to be the active sites for selectively forming phthalic anhydride.
Synthesis, characterization and electrocatalytic activity of silver nanorods ...tshankar20134
This document describes the synthesis of silver nanorods using a polyol process. Silver nitrate and polyvinylpyrrolidone (PVP) are reduced by propylene glycol at high temperature, allowing control over the diameter and length of the nanorods. Characterization with SEM, TEM, XRD and UV-vis spectroscopy confirms the formation of crystalline silver nanorods. Electrochemical testing shows that a glassy carbon electrode coated with silver nanorods exhibits high catalytic activity for the reduction of benzyl chloride, with a more positive reduction potential than bulk silver or plain glassy carbon electrodes. The extraordinary catalytic effect of the silver nanorods is likely due to their morphology and high affinity for chloride ions.
This document describes a study where Pt-Ru nanoparticles were supported on functionalized carbon nanofibers (CNF) using polyamidoamine (PAMAM) dendrimers. PAMAM dendrimers were anchored to carboxylated CNF and then used to encapsulate and disperse Pt-Ru nanoparticles on the CNF surface. The composite catalyst (20% Pt-Ru/PAMAM-CNF) showed better performance for methanol oxidation than a commercial 20% Pt-Ru/C catalyst based on cyclic voltammetry tests. Characterization with XRD, SEM and TEM showed the Pt-Ru nanoparticles were uniformly dispersed and small in size (2.6 nm) on the PA
Fabrication, morphology and structural characterization of tungsten oxide nan...tshankar20134
The document describes a method for synthesizing tungsten oxide nanorods. Phosphotungstic acid is infiltrated into an alumina membrane template and then calcined to form WO3 nanorods inside the template. The nanorods are characterized using SEM, TEM, AFM, XRD, Raman and IR spectroscopy. SEM and TEM images show the nanorods have a diameter of around 200nm, matching the pore size of the template. XRD and Raman patterns confirm the nanorods have a monoclinic crystalline structure. The nanorods also show superior electrochemical cycling ability compared to bulk WO3 materials.
Dynamic and equilibrium studies on the sorption of basic dyetshankar20134
This document summarizes a study on the adsorption of Basic Brown 4 dye onto multi-walled carbon nanotubes (MWNTs) prepared from renewable carbon precursors and commercial activated carbon. MWNTs were synthesized from pine oil, methyl ester of Jatropha curcas oil, and methyl ester of Pongamiya pinnata oil. Batch adsorption experiments were conducted to understand the effects of parameters like solution pH, contact time, temperature, and to evaluate adsorption kinetics and thermodynamics. Kinetic data fitted well to the pseudo-second order model. Adsorption was found to be spontaneous and endothermic in nature.
The document summarizes the synthesis and characterization of plumbum(II) complexes with mixed ligands of bis(N-alkyl-N-ethyldithiocarbamates) and 1,10-phenanthroline. Specifically, it describes the synthesis of new plumbum(II) complexes with butyl and cyclohexyl dithiocarbamate ligands and their adducts with phenanthroline. Elemental analysis, infrared spectroscopy, and 13C NMR spectroscopy were used to characterize the complexes and confirmed the proposed structures.
This document is a chapter from a general chemistry textbook titled "General Chemistry: Principles and Modern Applications" by Petrucci, Harwood, and Herring. The chapter is titled "Liquids, Solids and Intermolecular Forces" and covers topics such as the properties of liquids and solids, intermolecular forces like hydrogen bonding and van der Waals forces, phase diagrams, crystal structures of solids, and energy changes during phase changes. It includes diagrams to illustrate concepts like vapor pressure curves, phase diagrams, and crystal unit cells.
1) Atmospheric CO2 levels have risen from 280 ppm pre-industrially to over 410 ppm currently due to emissions from fossil fuel combustion and respiration. Maximum safe levels are believed to be 450 ppm or less to avoid worst effects of global warming and ocean acidification.
2) The document discusses strategies for converting CO2 into useful products like dimethyl carbonate (DMC), formic acid and methanol. It outlines more sustainable routes for producing these chemicals directly from CO2 rather than traditional methods that rely on other carbon sources.
3) Specifically, it presents a method for continuously producing pure formic acid by hydrogenating supercritical CO2 with an immobilized catalyst and base, avoiding high
This document is a chapter from a general chemistry textbook. It is chapter 6, which covers gases. The chapter contains 9 sections that discuss gas properties and laws, including gas pressure, the simple gas laws, the ideal gas equation, applications of the ideal gas equation like determining molar mass, gases in chemical reactions, mixtures of gases, kinetic molecular theory, gas properties related to kinetic molecular theory, and non-ideal gases. The chapter also includes sample problems and questions at the end.
This chapter of the general chemistry textbook discusses solubility and complex ion equilibria. It covers topics such as the solubility product constant Ksp, the common ion effect, limitations of Ksp, criteria for precipitation, fractional precipitation, effects of pH on solubility, and equilibria involving complex ions. It also describes the process of qualitative cation analysis using selective precipitation of cations in different solubility groups.
Density functional theory calculations were performed to investigate the structural, electronic, and CO2 adsorption properties of 55-atom bimetallic CuNi nanoparticles. The calculations revealed that decorated Cu12Ni43 and core-shell Cu42Ni13 configurations were more energetically favorable than the monometallic Cu55 and Ni55 nanoparticles. CO2 was found to chemisorb on Ni55, Cu13Ni42, Cu12Ni43, and Cu43Ni12 by undergoing a transition from linear to bent geometry and elongating the C=O bonds, while it only physisorbed on Cu55 and Cu42Ni13. The presence of surface Ni atoms played a key role in strongly adsorbing and activating CO
Maiyalagan,Performance of carbon nanofiber supported pd ni catalysts for elec...kutty79
Carbon nanofibers (CNF) supported Pd–Ni nanoparticles have been prepared by chemical reduction
with NaBH4 as a reducing agent. The Pd–Ni/CNF catalysts were characterized by X-ray diffraction
(XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical
voltammetry analysis. TEM showed that the Pd–Ni particles were quite uniformly distributed on the
surface of the carbon nanofiber with an average particle size of 4.0 nm. The electro-catalytic activity of
the Pd–Ni/CNF for oxidation of ethanol was examined by cyclic voltammetry (CV). The onset potential
was 200mV lower and the peak current density four times higher for ethanol oxidation for Pd–Ni/CNF
compared to that for Pd/C. The effect of an increase in temperature from 20 to 60 ◦C had a great effect on
increasing the ethanol oxidation activity
The peer-reviewed International Journal of Engineering Inventions (IJEI) is started with a mission to encourage contribution to research in Science and Technology. Encourage and motivate researchers in challenging areas of Sciences and Technology.
This document describes a computational fluid dynamics (CFD) study of methane decomposition into hydrogen and solid carbon in a packed bed fluid catalytic cracking (FCC) reactor. The study used CFD modeling in COMSOL Multiphysics to simulate the decomposition reaction over time in the packed bed reactor. Results showed that increasing the reaction time from 0 to 1000 seconds increased the production of hydrogen from 0 to 42 mol/dm3 and carbon from 0 to 21 mol/dm3, while decreasing methane concentration from 50 to 29 mol/dm3, indicating that decomposition was occurring. Spatial profiles of velocity, concentration, pressure and permeability within the reactor were also determined and discussed.
Deposition of ni ti n coatings by a plasma assisted mocvd using an organometa...tshankar20134
Titanium nitride (TiN)/nickel (Ni) composite coatings were synthesized by plasma assisted metal-organic
chemical vapour deposition (PAMOCVD) using organo-metallic and metal-organic complexes namely dichlorobis(5-
cyclopentadienyl)titanium (IV) for titanium and N,N'-ethylene-bis(2,4-pentanedion-iminoato)nickel(II) for nickel. The
growth of such films was investigated in nitrogen (N2) plasma environment in the substrate temperature range of 450-
550ºC at a deposition pressure of 0.5-1 mbar. Prior to the deposition of films, the Ti precursor was subjected to the
equilibrium vapour pressure measurements by employing TG/DTA in transpiration mode, which led to the value of 109.2
± 5.6 kJ mol-1 for the standard enthalpy of sublimation (Ho
sub). The phase identification using glancing incidence x-ray
diffraction showed Ni/TiN is a nanocomposite coating containing nanocrystals of Ni and TiN with face centered cubic
structure. Scanning electron microscopy revealed a uniform surface morphology of the films, while chemical analysis by
energy dispersive analysis confirmed the presence of titanium, nickel and nitrogen in the composite films.
Nanostructured fe2 o3 platform for the electrochemical sensing of folic acidtshankar20134
The document describes the synthesis of alpha-iron oxide (α-Fe2O3) nanofibers using a simple electrospinning method and their application for the electrochemical sensing of folic acid (FA). The α-Fe2O3 nanofiber-modified glassy carbon electrode showed good selectivity for detecting FA even in the presence of ascorbic acid, achieving a detection limit of 60 nM for FA. The α-Fe2O3 nanofibers provided a high surface area platform and enhanced the oxidation current and separation of voltammetric signals for FA and ascorbic acid compared to an unmodified electrode. The modified electrode was successfully used to determine FA concentrations in human blood serum samples.
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.
Electro catalytic performance of pt-supported poly (o-phenylenediamine) micro...tshankar20134
This document summarizes research on developing a nanocomposite catalyst of Pt supported on poly(o-phenylenediamine) (PoPD) microrods for electro-oxidation of methanol in fuel cells. PoPD microrods were synthesized through an interfacial polymerization method using ferric chloride. Pt nanoparticles were deposited on the PoPD microrods using sodium borohydride reduction of chloroplatinic acid. Characterization with XRD showed the Pt had a face-centered cubic structure. Electrochemical tests found the Pt/PoPD catalyst had higher catalytic activity and stability for methanol oxidation compared to a Pt/carbon catalyst, which may be due to the microrod morphology facilitating better
Template synthesis and characterization of well aligned nitrogen containing c...tshankar20134
This document describes the synthesis and characterization of nitrogen-containing carbon nanotubes produced through the pyrolysis of polyvinyl pyrrolidone on an alumina membrane template. The nanotubes were analyzed using various techniques which showed they had a hollow, vertically aligned structure with a significant amount of nitrogen incorporated into the carbon framework, as evidenced by elemental analysis, Raman spectroscopy, IR spectroscopy, and XPS. The template synthesis method allowed production of well-aligned nitrogen-containing carbon nanotubes with controlled morphology and composition.
One pot synthesis of chain-like palladium nanocubes and their enhanced electr...tshankar20134
This document describes a one-pot synthesis of chain-like palladium nanocubes and their enhanced electrocatalytic activity. A simple aqueous approach is used to produce anisotropic cubic chain-like Pd nanostructures using the neurotransmitter 5-hydroxytryptamine. Scanning electron microscopy images show the nanocubes have sizes between 140-210 nm and form chain-like branched structures. Testing shows the cubic chain-like nanostructures have over 11 times greater electrocatalytic activity for oxidizing formic acid, methanol, and ethanol compared to spherical nanoparticles and commercial Pd/C catalysts. The enhanced performance makes them promising multipurpose catalysts for direct fuel cells.
Highly stable pt–ru nanoparticles supported on three dimensional cubic ordere...tshankar20134
This document describes the synthesis and characterization of Pt-Ru nanoparticles supported on cubic ordered mesoporous carbon (Pt-Ru/CMK-8) and their evaluation as electrocatalysts for methanol oxidation in direct methanol fuel cells. Two types of CMK-8 carbon with different pore sizes were synthesized using two different mesoporous silica templates. Pt-Ru was deposited on the CMK-8 using sodium borohydride reduction. Characterization showed the CMK-8 had high surface areas over 1000 m2/g and pore volumes over 1.26 cm3/g. Electrochemical testing found the Pt-Ru/CMK-8-I catalyst had a high specific mass activity of 487
V mn-mcm-41 catalyst for the vapor phase oxidation of o-xylenetshankar20134
This document summarizes research on V-Mn-MCM-41 catalysts for the vapor phase oxidation of o-xylene. Mesoporous monometallic and bimetallic catalysts with varying ratios of vanadium and manganese were synthesized and characterized. Their activity for oxidizing o-xylene to phthalic anhydride was measured and found to correlate with their physical and chemical properties. The V-MCM-41 catalyst with a Si/V ratio of 50 exhibited the highest activity and selectivity. Vanadium species in the +5 oxidation state within the MCM-41 silica matrix were determined to be the active sites for selectively forming phthalic anhydride.
Synthesis, characterization and electrocatalytic activity of silver nanorods ...tshankar20134
This document describes the synthesis of silver nanorods using a polyol process. Silver nitrate and polyvinylpyrrolidone (PVP) are reduced by propylene glycol at high temperature, allowing control over the diameter and length of the nanorods. Characterization with SEM, TEM, XRD and UV-vis spectroscopy confirms the formation of crystalline silver nanorods. Electrochemical testing shows that a glassy carbon electrode coated with silver nanorods exhibits high catalytic activity for the reduction of benzyl chloride, with a more positive reduction potential than bulk silver or plain glassy carbon electrodes. The extraordinary catalytic effect of the silver nanorods is likely due to their morphology and high affinity for chloride ions.
This document describes a study where Pt-Ru nanoparticles were supported on functionalized carbon nanofibers (CNF) using polyamidoamine (PAMAM) dendrimers. PAMAM dendrimers were anchored to carboxylated CNF and then used to encapsulate and disperse Pt-Ru nanoparticles on the CNF surface. The composite catalyst (20% Pt-Ru/PAMAM-CNF) showed better performance for methanol oxidation than a commercial 20% Pt-Ru/C catalyst based on cyclic voltammetry tests. Characterization with XRD, SEM and TEM showed the Pt-Ru nanoparticles were uniformly dispersed and small in size (2.6 nm) on the PA
Fabrication, morphology and structural characterization of tungsten oxide nan...tshankar20134
The document describes a method for synthesizing tungsten oxide nanorods. Phosphotungstic acid is infiltrated into an alumina membrane template and then calcined to form WO3 nanorods inside the template. The nanorods are characterized using SEM, TEM, AFM, XRD, Raman and IR spectroscopy. SEM and TEM images show the nanorods have a diameter of around 200nm, matching the pore size of the template. XRD and Raman patterns confirm the nanorods have a monoclinic crystalline structure. The nanorods also show superior electrochemical cycling ability compared to bulk WO3 materials.
Dynamic and equilibrium studies on the sorption of basic dyetshankar20134
This document summarizes a study on the adsorption of Basic Brown 4 dye onto multi-walled carbon nanotubes (MWNTs) prepared from renewable carbon precursors and commercial activated carbon. MWNTs were synthesized from pine oil, methyl ester of Jatropha curcas oil, and methyl ester of Pongamiya pinnata oil. Batch adsorption experiments were conducted to understand the effects of parameters like solution pH, contact time, temperature, and to evaluate adsorption kinetics and thermodynamics. Kinetic data fitted well to the pseudo-second order model. Adsorption was found to be spontaneous and endothermic in nature.
Electrodeposited pt on three dimensional interconnected graphene as a free st...tshankar20134
The document summarizes research on using a three-dimensional interconnected graphene structure as an electrode support for platinum nanoparticles for fuel cell applications. Key points:
1) Graphene was grown into a 3D foam-like structure using chemical vapor deposition on a nickel foam template, creating a seamless porous structure with high surface area and conductivity.
2) Platinum nanoparticles were deposited on the 3D graphene using pulsed electrodeposition, allowing control over particle size and uniform dispersion.
3) The 3D graphene with platinum nanoparticles showed improved catalytic activity for methanol oxidation compared to carbon fibers, due to the unique 3D structure, high surface area, and high conductivity of the graphene support.
Film pore diffusion modeling for sorption of azo dye on to exfoliated graphit...tshankar20134
This document summarizes a study on the adsorption of the azo dye Acid Orange 7 onto exfoliated graphitic nanoplatelets (xGnPs) as a potential adsorbent. The effects of temperature, initial dye concentration, and pH on the adsorption process were investigated. Kinetic models including pseudo-first order, pseudo-second order and Elovich equation were applied and the data fit best with the pseudo-second order model, indicating chemisorption. Equilibrium studies showed the adsorption data fit well with both Langmuir and Freundlich isotherm models. The maximum adsorption capacity was found to increase with decreasing temperature, indicating an exothermic process.
Nitrogen review on recent progress in nitrogen-doped graphene synthesis, cha...sunidevi
Nitrogen doping has been an effective way to
tailor the properties of graphene and render its potential use
for various applications. Three common bonding configurations
are normally obtained when doping nitrogen into the
graphene: pyridinic N, pyrrolic N, and graphitic N. This paper
reviews nitrogen-doped graphene, including various synthesis
methods to introduce N doping and various characterization
techniques for the examination of various N bonding
configurations. Potential applications of N-graphene are also
reviewed on the basis of experimental and theoretical studies.
A review on recent progress in nitrogen doped graphene synthesis, characteriz...sunilove
This document reviews recent progress in nitrogen-doped graphene, including various synthesis methods to introduce nitrogen doping, characterization techniques to examine nitrogen bonding configurations, and potential applications. Common nitrogen bonding configurations in graphene are pyridinic nitrogen, pyrrolic nitrogen, and graphitic/quaternary nitrogen. Nitrogen doping can tailor graphene's properties and enable applications in electrocatalysis, field-effect transistors, energy storage, and more. The document surveys 21 different synthesis methods for producing nitrogen-doped graphene and discusses their achieved nitrogen doping levels.
1) Nitrogen doping is an effective way to modify the properties of graphene. There are three common types of nitrogen bonding configurations: pyridinic N, pyrrolic N, and graphitic N.
2) Nitrogen-doped graphene (N-graphene) can be synthesized via direct methods like CVD and solvothermal synthesis or via post-treatment methods like thermal treatment and plasma treatment.
3) Different synthesis methods produce N-graphene with varying nitrogen content and bonding configurations, which impact the material's properties and potential applications in areas like energy storage, sensors, and electronics.
A review on recent progress in nitrogen doped graphene synthesis, characteriz...suresh800
This document reviews recent progress in nitrogen-doped graphene, including various synthesis methods to introduce nitrogen doping, characterization techniques to examine nitrogen bonding configurations, and potential applications. Common nitrogen bonding configurations in graphene are pyridinic nitrogen, pyrrolic nitrogen, and graphitic/quaternary nitrogen. Nitrogen doping can tailor graphene's properties and enable applications in electrocatalysis, field-effect transistors, energy storage, and more. The document surveys 21 different synthesis methods for producing nitrogen-doped graphene and discusses their achieved nitrogen doping levels.
A review on recent progress in nitrogen doped graphene synthesis, characteriz...Science Padayatchi
This document reviews recent progress in nitrogen-doped graphene, including various synthesis methods to introduce nitrogen doping, characterization techniques to examine nitrogen bonding configurations, and potential applications. Common nitrogen bonding configurations in graphene are pyridinic nitrogen, pyrrolic nitrogen, and graphitic/quaternary nitrogen. The document summarizes 21 different methods used to synthesize nitrogen-doped graphene and the resulting nitrogen content, and discusses how nitrogen doping can tailor graphene's properties for applications in areas like electrocatalysis, transistors, energy storage, and sensors.
CVD grown nitrogen doped graphene is an exceptional visible-light driven phot...Pawan Kumar
This document summarizes research on nitrogen-doped graphene (NGr) and its potential as a visible-light photocatalyst. Key points:
- NGr was synthesized using chemical vapor deposition with acetonitrile as the carbon and nitrogen source. Nitrogen doping introduces a bandgap and increases the chemical reactivity of graphene.
- Silver nanoparticles were synthesized to form NGr/Ag nanohybrids. Under visible light, plasmonic effects in silver nanoparticles and excitonic effects in NGr interact, generating "hot electrons" that increase photocatalytic activity.
- The photocatalytic performance of NGr, NGr/Ag nanohybrids, and
CVD grown nitrogen doped graphene is an exceptional visible-light driven phot...Pawan Kumar
The photocatalytic potential of large area CVD grown nitrogen doped graphene (NGr) has been explored though the chemical transformation of 4-nitrobenzene thiol into p,p'-dimercaptoazobenzene. Decoration of NGr with Ag nanocubes with rounded edges to form NGr/Ag nanohybrids resulted in a slight increase in the work-function and a decrease in the n-type character of NGr due to ground state transfer of negative charge from NGr to Ag. The Ag nanocubes exhibited a localized surface plasmon resonance (LSPR) at ~425 nm. When the NGr/Ag nanohybrids were illuminated with visible light of wavelength close to the LSPR peak, Kelvin probe force microscopy (KPFM) indicated a dramatic change in surface potential of −225 mV and Raman spectra detected electron accumulation in NGr, which are attributed to a high local field enhancement-mediated hot electron injection into NGr and the formation of long-lived charge separated states. Pristine nitrogen doped graphene and its coupled system with plasmonic Ag nanoparticles showed superior photocatalytic performance compared to bare plasmonic Ag catalyst. While standalone Ag NPs were unable to complete the transformation of 4-NBT into DMAB even at a laser power of 10 mW, NGr/Ag nanohybrids completed this transformation at a laser power of 1 mW, pointing to the high photoreduction strength of NGr/Ag. Density functional theory (DFT) based computational modeling was used to examine the electronic structure of graphene doped with graphitic, pyridinic and pyrrolic nitrogen dopant atoms. DFT results indicated an enhanced chemical reactivity of NGr due to stronger localization of charge at the dopant sites and a pronounced difference in the projected density of states (PDOS) for carbon atoms in proximity to, and distant from, the nitrogen dopant sites.
This document describes research on nitrogen-doped vertical graphene (N-VG) as a metal-free electrocatalyst for the hydrogen evolution reaction (HER). N-VG was synthesized by a simple ammonia treatment of vertical graphene (VG). Characterization shows the nitrogen doping introduces defects but maintains the VG morphology. Electrochemical tests reveal the N-VG has enhanced HER performance over VG, with an overpotential of 290 mV at 10 mA/cm2 and a Tafel slope of 121 mV/decade. Density functional theory calculations provide insight into how nitrogen doping can optimize the electronic structure and introduce new active sites to improve the HER activity of N-VG.
Nitrogen doped graphene nanosheet supported platinum nanoparticles as high pe...Science Padayatchi
Functional carbon nanomaterials are significantly important for the development of high performance
sensitive and selective electrochemical biosensors. In this study, graphene supported platinum
nanoparticles (GN–PtNPs) and nitrogen doped graphene supported platinum nanoparticles (N-GN–
PtNPs) were synthesized by a simple chemical reduction method and explored as high performance
nanocatalyst supports, as well as doped nanocatalyst supports, toward electrochemical oxidation of
homocysteine (HCY) for the first the time. Our studies demonstrate that N-doped graphene supported
PtNPs show higher electrocatalytic activity for HCY with an experimental detection limit of 200 pM.
Moreover, N-doped graphene supported Pt was demonstrated to have excellent selectivity in the
electrochemical oxidation of HCY i.e., the detection of HCY is successful in the presence of a 20-fold
excess of ascorbic acid (AA). The practical application of N-doped graphene supported PtNP materials is
effectively shown for the determination of HCY in both human blood serum and urine samples, by
differential pulse voltammetry under optimized conditions. Our findings conclude that N-doped
graphene supported PtNPs can be developed as a high performance and versatile nano-electrocatalyst
for electrochemical biosensor applications.
Spectroscopy, Infrared Spectroscopy And SpectroscopyMelissa Moore
Spectroscopy is a broad field that includes techniques like Raman spectroscopy, infrared spectroscopy, NMR spectroscopy, and optical spectroscopy. These techniques involve using electromagnetic radiation to interact with and study matter. Infrared spectroscopy can help identify functional groups in a molecule by examining how the molecule vibrates when exposed to infrared light. NMR spectroscopy provides information about the molecular structure by measuring magnetic properties of atomic nuclei and how they interact with applied magnetic fields. Data from NMR indicates the number of protons and their chemical environment, aiding in determining molecular structure.
Biological and Medical Applications of Graphene NanoparticlesAI Publications
Graphene which is one of the latest additions to nanocarbon family has peculiar band structure, extraordinary thermal and electronic conductance and room temperature quantum Hall effect. It is used in for various applications in diverse fields ranging from catalysis to electronics. In addition to being components in electronic devices, GO have been used in nanocomposite materials, polymer composite materials, energy storage, biomedical applications, catalysis and as a surfactant with some overlaps between these fields Graphene oxide is a unique material that can be viewed as a single monomolecular layer of graphite with various oxygen containing functionalities such as epoxide, carbonyl, carboxyl and hydroxyl groups.
C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Fra...Pawan Kumar
Modification of carbon nitride based polymeric 2D materials for tailoring their optical, electronic and chemical properties for various applications has gained significant interest. The present report demonstrates the synthesis of a novel modified carbon nitride framework with a remarkable 3:5 C:N stoichiometry (C3N5) and an electronic bandgap of 1.76 eV, by thermal deammoniation of the melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units are bridged together with azo linkage, which constitutes an entirely new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen. Extended conjugation due to overlap of azo nitrogens and increased electron density on heptazine nucleus due to the aromatic π network of heptazine units lead to an upward shift of the valence band maximum resulting in bandgap reduction
C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Fra...Pawan Kumar
This document describes the synthesis and characterization of a novel carbon nitride framework called C3N5. C3N5 has a 3:5 carbon to nitrogen stoichiometry and is synthesized by thermal deammoniation of melem hydrazine. Characterization reveals that in the C3N5 polymer, two s-heptazine units are bridged together with an azo linkage. This azo linkage extends the π-conjugated network and lowers the electronic bandgap to 1.76 eV compared to 2.7 eV for g-C3N4. Due to its lower bandgap and electron-rich character, C3N5 shows improved performance for applications in solar cells, photocatalysis
CHARACTERIZATION AND APPLICATION OF GRAPHENE OXIDE AND GRAPHENE NITRIDENirmalKumar596
I UPLOADED MY POWERPOINT PRESENTATION ABOUT THE GRAPHENE CHARACTERISTICS AND ITS APPLICATIONS
OUR PEOPLE WILL LEARN THESE AND UNDERSTANDS FEW BASIC THINGS ABOUT GRAPHENE
I COMPLETED MY PROJECT IN SANKARA NETHRALAYA IN MARCH 2020
GRAPHENE CAN BE USED FOR BIOTECH INDUSTRIES AS WELL AS RESEARCH AND DEVELOPMENT
Nickel Decorated on Phosphorous-Doped Carbon Nitride as an Efficient Photocat...Pawan Kumar
Nickel nanoparticle-decorated phosphorous-doped graphitic carbon nitride (Ni@g-PC3N4)
was synthesized and used as an efficient photoactive catalyst for the reduction of various
nitrobenzenes under visible light irradiation. Hydrazine monohydrate was used as the source
of protons and electrons for the intended reaction. The developed photocatalyst was found to be
highly active and afforded excellent product yields under mild experimental conditions. In addition,
the photocatalyst could easily be recovered and reused for several runs without any detectable
leaching during the reaction.
This document summarizes research on graphene-based composite materials and their applications in energy storage devices and sensors. It discusses how graphene possesses unique electronic and mechanical properties and can be produced through various methods. Graphene composites with conducting polymers and metal oxides have been used in supercapacitors and shown to provide high specific capacitance values. Graphene composites have also been applied as electrode materials in lithium-ion batteries, demonstrating high reversible capacity and cycling stability. Additionally, graphene composites with metals like platinum and gold have been investigated as electrocatalysts for fuel cells.
This study uses density functional theory calculations to examine the interaction between titanium oxide nanostructures and graphene or functionalized graphene nanoribbons (GNRs). The key findings are:
1) Rutile titanium dioxide favors physisorption on pure graphene, while rutile and anatase titanium dioxide show similar chemisorption on functionalized GNRs.
2) Charge density maps show the importance of electron distribution in the chemical interaction between titanium dioxide and graphene.
3) Analysis of partial density of states reveals the strength of binding energies at specific adsorption sites on the titanium dioxide/graphene systems.
4) The results provide insight into controlled growth mechanisms that could have applications in photovolta
Final Report (Graphene supported platinum nanoparticles) (1)Sridharan Thirumalai
This document is a student project report on platinum-graphene nanocomposites as electrocatalysts in PEM fuel cells. It was submitted by T.V. Sridharan to Professor Manoj Neergat at the Indian Institute of Technology, Bombay under his supervision. The report describes the synthesis of Pt/rGO nanocomposites using a modified polyol method, and their physical and electrochemical characterization. TEM analysis showed the successful deposition of platinum nanoparticles on graphene oxide sheets. Electrochemical experiments found the Pt/rGO composite had a higher effective surface area than Pt/C, but similar activity for the oxygen reduction reaction. Further research is needed to fully realize graphene's potential as
ABSTRACT: In our previous article, the geometrical optimizations have been performed for the (CaO)n, n = 1-
4, 6, 8, 9, and 12 cluster models, [WJERT, 2019, 5 (1), 328-341]. In this study,we have investigated the
adsorption of performance NO2gas towards metal oxide clusters (CaO)n, n = 2, 3, 4, 6, 8, 9, 12) cluster models,
and focus on electron transfer between the CaO and NO2 molecule by employing density functional theory
(DFT), B3LYP method. Results show that the charge transferred goes from surface clusters to NO2 antibonding orbitals which makes more reactive, and becomes stronger. Moreover, NO2 adsorbs at the one, two
Ca2+sites forming a nitrite (NO2
−). Meanwhile, the interaction of NO2 with Lewis baseO
2−,and consequently may
form a nitrate (NO3
2−) species, which is less adsorption favorable. The total adsorption energies revealed that
NO2 gas was strongly chemisorbed on the(CaO)n, n = 2, 4, 6 and 8cluster models, whereas (CaO)n, n=3, 9 and
12 results in a weak interactions. Further, the results of optimized structure showed that the total adsorption
energies and charge transfer contributions indicated that CaO is a better acid-base than MgO, due to the
increasing basicity and bigger cationic size of the CaO. The reason for these different basicities and reactivates
can be ascribed to the different electrostatic (Madelung) potentials at the two surfaces.
Theoretical study of two dimensional Nano sheet for gas sensing applicationvivatechijri
This study is focus on various two dimensional material for sensing various gases with theoretical
view for new research in gas sensing application. In this paper we review various two dimensional sheet such as
Graphene, Boron Nitride nanosheet, Mxene and their application in sensing various gases present in the
atmosphere.
Similar to Nitrogen review on recent progress in nitrogen-doped graphene synthesis, characterization, and its potential applications (20)
Synthesis and optimisation of ir o2 electrocatalysts by adams fusion method f...tshankar20134
The document summarizes research into optimizing IrO2 as an electrocatalyst for oxygen evolution in solid polymer electrolyte electrolyzers. IrO2 was synthesized using the Adams fusion method, varying synthesis duration from 0.5-4 hours and temperature from 250-500°C. Characterization showed that increasing duration and temperature increased crystallinity and particle size. Electrochemical testing found that IrO2 synthesized for 2 hours at 350°C had the best catalytic activity for oxygen evolution, outperforming a commercial IrO2. Higher temperatures favored formation of the active IrO2 phase but also led to larger particle sizes which decreased activity. Lower than 350°C did not favor IrO2 formation.
Synthesis and electro catalytic activity of methanol oxidation on nitrogen co...tshankar20134
The document summarizes research on synthesizing nitrogen-containing carbon nanotubes using different nitrogen-containing polymers as templates. Platinum particles were then supported on these nitrogen-containing carbon nanotubes and on regular carbon nanotubes and carbon for comparison. Characterization showed the nitrogen-containing carbon nanotube supported platinum catalyst had higher catalytic activity for methanol oxidation than the other catalysts. This was attributed to the existence of additional active sites on the nitrogen-containing carbon nanotube surface, which improved platinum particle dispersion and metal-support interaction.
The document summarizes research on nano-structured lanthanum (La)-doped zinc oxide (ZnO) prepared using a combustion method. Coral-shaped ZnO nanostructures with pore sizes of 10-50 nm were successfully synthesized. Transmission electron microscopy showed the coral shape and porous nature increased with higher La doping concentrations. X-ray diffraction analysis confirmed the wurtzite structure of pure and doped ZnO. Optical studies showed absorbance in the UV region decreased and band gap increased with higher La doping levels. Photoluminescence spectra exhibited La characteristic emission and a shift in emission with doping. The La-doped ZnO nanostructures showed potential for applications in chemical sensing,
Nitrogen containing carbon nanotubes as supports fortshankar20134
1) Nitrogen-containing carbon nanotubes were synthesized and used to support platinum nanoparticles as an alternative anode catalyst for direct methanol fuel cells.
2) The platinum nanoparticles were uniformly distributed on the nitrogen-containing carbon nanotube surface with an average particle size of 3 nm.
3) Cyclic voltammetry studies showed that the platinum nanoparticles supported on nitrogen-containing carbon nanotubes had significantly higher catalytic activity for methanol oxidation compared to a commercial platinum on carbon catalyst.
Nitrogen containing carbon nanotubes as supports for pt–alternate anodes for ...tshankar20134
1) Nitrogen-containing carbon nanotubes were synthesized and used to support platinum nanoparticles as an alternative anode catalyst for direct methanol fuel cells.
2) The platinum nanoparticles were uniformly distributed on the nitrogen-containing carbon nanotube surface with an average particle size of 3 nm.
3) Cyclic voltammetry studies showed that the platinum nanoparticles supported on nitrogen-containing carbon nanotubes had higher catalytic activity for methanol oxidation compared to a conventional platinum on carbon black catalyst.
Green synthesis of well dispersed nanoparticles using leaf extract of medicin...tshankar20134
Green synthesis of gold nanoparticles was achieved using an extract of the medicinal plant Adhatoda vasica.
The nanoparticles formed were predominantly spherical and monodisperse, with sizes ranging from 22 to 47 nm as determined through transmission electron microscopy analysis. Ultraviolet-visible spectroscopy and X-ray diffraction data confirmed the formation and crystalline nature of the gold nanoparticles. Functional groups present in the plant extract, such as hydroxyl and carboxyl groups, were found to play a role in both the reduction of gold ions and stabilization of the resulting nanoparticles. This green synthesis method using A. vasica extract could provide a means of producing biocompatible gold nanoparticles for applications such as drug delivery.
Equilibrium and kinetic studies on the adsorption of methylene blue from aqueoustshankar20134
The document summarizes a study on the adsorption of the dye methylene blue from aqueous solution using activated carbon prepared from Murraya koenigii stems. Some key findings:
1) The activated carbon was characterized and found to have a specific surface area of 508 m2/g and pore structure consisting of micro and mesopores suitable for adsorption.
2) Batch adsorption experiments showed that adsorption capacity increased with increasing adsorbent dosage, reaching 98.99% dye removal at 0.12g dosage.
3) Equilibrium data fitted well to Langmuir and Temkin isotherm models, indicating monolayer adsorption occurred with a maximum adsorption capacity of 123
Electro oxidation of methanol on ti o2 nanotube supported platinum electrodestshankar20134
This document summarizes research on using TiO2 nanotubes as a support for platinum nanoparticles for use as an electrocatalyst in methanol fuel cells. TiO2 nanotubes were synthesized using anodic aluminum oxide as a template. Platinum nanoparticles 3-4 nm in size were uniformly dispersed on the TiO2 nanotube supports. Electrochemical testing found that platinum nanoparticles supported on TiO2 nanotubes had higher catalytic activity for methanol oxidation compared to commercial Pt/C catalysts, with mass activity over 33 mA/mg Pt versus 3.25 mA/mg Pt for Pt/C. The improved activity is attributed to the TiO2 support preventing CO poisoning of platinum sites and possible electronic interactions between
Electrooxidation of methanol on carbon supported pt ru nanocatalysts prepared...tshankar20134
The document describes a study that prepared carbon-supported PtRu nanocatalysts using an ethanol reduction method for different reaction times. The catalysts were characterized using various techniques and tested for their electrocatalytic activity in methanol oxidation. XRD and TEM analysis showed the catalysts had an FCC structure with an average particle size of 3.7 nm. Cyclic voltammetry tests found that the catalyst prepared at a 2h reduction time had higher electrocatalytic activity and stability for methanol electrooxidation compared to the other catalysts. The results suggest these catalysts could be promising anode catalysts for direct methanol fuel cells.
This document summarizes research on developing Pt/V2O5-C composite catalysts for methanol oxidation in direct methanol fuel cells (DMFCs). Pt nanoparticles were dispersed on a V2O5-C composite support through chemical reduction. The catalyst was characterized using XRD and TEM, which showed the formation of small Pt nanoparticles (~3 nm) on the support. Electrochemical testing showed that the Pt/V2O5-C composite catalyst had higher catalytic activity for methanol oxidation compared to a commercial Pt/C catalyst, as indicated by a more positive onset potential and higher forward/reverse peak current ratios. The composite catalyst also demonstrated comparable stability during chronoamperometry testing. The improved performance is attributed to
Effects of heat treatment on the catalytic activity and methanol tolerance of...tshankar20134
This document studies the effects of heat treatment on the catalytic activity and methanol tolerance of carbon-supported platinum alloys. Platinum (Pt), platinum-cobalt (Pt-Co), platinum-copper (Pt-Cu), platinum-iron (Pt-Fe), and platinum-nickel (Pt-Ni) catalysts were heat treated at different temperatures and their properties were analyzed. Heat treatment was found to increase particle size but also improved catalytic activity in most cases. The optimum heat treatment temperature depended on the specific catalyst. Pt-Cu/C and Pt-Fe/C catalysts heat treated at 350°C showed the highest oxygen reduction reaction activity and best methanol tolerance. Overall, Pt-
Components of pem_fuel_cells_an_overviewtshankar20134
The document provides an overview of the key components of proton exchange membrane fuel cells (PEMFCs). PEMFCs consist of a membrane electrode assembly (MEA) with a proton-conducting membrane sandwiched between two electrode layers. Perfluorinated sulfonic acid membranes like Nafion are most widely used as they have high proton conductivity while preventing fuel/oxidant mixing. Efforts are ongoing to develop alternative membranes and electrocatalysts to reduce costs and improve durability in order to facilitate PEMFC commercialization for applications like transportation.
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfPaige Cruz
Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
I, a former op, would like to extend an invitation to all application developers to join the observability party will share these foundational concepts to build on:
Climate Impact of Software Testing at Nordic Testing DaysKari Kakkonen
My slides at Nordic Testing Days 6.6.2024
Climate impact / sustainability of software testing discussed on the talk. ICT and testing must carry their part of global responsibility to help with the climat warming. We can minimize the carbon footprint but we can also have a carbon handprint, a positive impact on the climate. Quality characteristics can be added with sustainability, and then measured continuously. Test environments can be used less, and in smaller scale and on demand. Test techniques can be used in optimizing or minimizing number of tests. Test automation can be used to speed up testing.
Maruthi Prithivirajan, Head of ASEAN & IN Solution Architecture, Neo4j
Get an inside look at the latest Neo4j innovations that enable relationship-driven intelligence at scale. Learn more about the newest cloud integrations and product enhancements that make Neo4j an essential choice for developers building apps with interconnected data and generative AI.
Cosa hanno in comune un mattoncino Lego e la backdoor XZ?Speck&Tech
ABSTRACT: A prima vista, un mattoncino Lego e la backdoor XZ potrebbero avere in comune il fatto di essere entrambi blocchi di costruzione, o dipendenze di progetti creativi e software. La realtà è che un mattoncino Lego e il caso della backdoor XZ hanno molto di più di tutto ciò in comune.
Partecipate alla presentazione per immergervi in una storia di interoperabilità, standard e formati aperti, per poi discutere del ruolo importante che i contributori hanno in una comunità open source sostenibile.
BIO: Sostenitrice del software libero e dei formati standard e aperti. È stata un membro attivo dei progetti Fedora e openSUSE e ha co-fondato l'Associazione LibreItalia dove è stata coinvolta in diversi eventi, migrazioni e formazione relativi a LibreOffice. In precedenza ha lavorato a migrazioni e corsi di formazione su LibreOffice per diverse amministrazioni pubbliche e privati. Da gennaio 2020 lavora in SUSE come Software Release Engineer per Uyuni e SUSE Manager e quando non segue la sua passione per i computer e per Geeko coltiva la sua curiosità per l'astronomia (da cui deriva il suo nickname deneb_alpha).
Sudheer Mechineni, Head of Application Frameworks, Standard Chartered Bank
Discover how Standard Chartered Bank harnessed the power of Neo4j to transform complex data access challenges into a dynamic, scalable graph database solution. This keynote will cover their journey from initial adoption to deploying a fully automated, enterprise-grade causal cluster, highlighting key strategies for modelling organisational changes and ensuring robust disaster recovery. Learn how these innovations have not only enhanced Standard Chartered Bank’s data infrastructure but also positioned them as pioneers in the banking sector’s adoption of graph technology.
Dr. Sean Tan, Head of Data Science, Changi Airport Group
Discover how Changi Airport Group (CAG) leverages graph technologies and generative AI to revolutionize their search capabilities. This session delves into the unique search needs of CAG’s diverse passengers and customers, showcasing how graph data structures enhance the accuracy and relevance of AI-generated search results, mitigating the risk of “hallucinations” and improving the overall customer journey.
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024Neo4j
Neha Bajwa, Vice President of Product Marketing, Neo4j
Join us as we explore breakthrough innovations enabled by interconnected data and AI. Discover firsthand how organizations use relationships in data to uncover contextual insights and solve our most pressing challenges – from optimizing supply chains, detecting fraud, and improving customer experiences to accelerating drug discoveries.
GraphRAG for Life Science to increase LLM accuracyTomaz Bratanic
GraphRAG for life science domain, where you retriever information from biomedical knowledge graphs using LLMs to increase the accuracy and performance of generated answers
Communications Mining Series - Zero to Hero - Session 1DianaGray10
This session provides introduction to UiPath Communication Mining, importance and platform overview. You will acquire a good understand of the phases in Communication Mining as we go over the platform with you. Topics covered:
• Communication Mining Overview
• Why is it important?
• How can it help today’s business and the benefits
• Phases in Communication Mining
• Demo on Platform overview
• Q/A
In the rapidly evolving landscape of technologies, XML continues to play a vital role in structuring, storing, and transporting data across diverse systems. The recent advancements in artificial intelligence (AI) present new methodologies for enhancing XML development workflows, introducing efficiency, automation, and intelligent capabilities. This presentation will outline the scope and perspective of utilizing AI in XML development. The potential benefits and the possible pitfalls will be highlighted, providing a balanced view of the subject.
We will explore the capabilities of AI in understanding XML markup languages and autonomously creating structured XML content. Additionally, we will examine the capacity of AI to enrich plain text with appropriate XML markup. Practical examples and methodological guidelines will be provided to elucidate how AI can be effectively prompted to interpret and generate accurate XML markup.
Further emphasis will be placed on the role of AI in developing XSLT, or schemas such as XSD and Schematron. We will address the techniques and strategies adopted to create prompts for generating code, explaining code, or refactoring the code, and the results achieved.
The discussion will extend to how AI can be used to transform XML content. In particular, the focus will be on the use of AI XPath extension functions in XSLT, Schematron, Schematron Quick Fixes, or for XML content refactoring.
The presentation aims to deliver a comprehensive overview of AI usage in XML development, providing attendees with the necessary knowledge to make informed decisions. Whether you’re at the early stages of adopting AI or considering integrating it in advanced XML development, this presentation will cover all levels of expertise.
By highlighting the potential advantages and challenges of integrating AI with XML development tools and languages, the presentation seeks to inspire thoughtful conversation around the future of XML development. We’ll not only delve into the technical aspects of AI-powered XML development but also discuss practical implications and possible future directions.
Threats to mobile devices are more prevalent and increasing in scope and complexity. Users of mobile devices desire to take full advantage of the features
available on those devices, but many of the features provide convenience and capability but sacrifice security. This best practices guide outlines steps the users can take to better protect personal devices and information.
TrustArc Webinar - 2024 Global Privacy SurveyTrustArc
How does your privacy program stack up against your peers? What challenges are privacy teams tackling and prioritizing in 2024?
In the fifth annual Global Privacy Benchmarks Survey, we asked over 1,800 global privacy professionals and business executives to share their perspectives on the current state of privacy inside and outside of their organizations. This year’s report focused on emerging areas of importance for privacy and compliance professionals, including considerations and implications of Artificial Intelligence (AI) technologies, building brand trust, and different approaches for achieving higher privacy competence scores.
See how organizational priorities and strategic approaches to data security and privacy are evolving around the globe.
This webinar will review:
- The top 10 privacy insights from the fifth annual Global Privacy Benchmarks Survey
- The top challenges for privacy leaders, practitioners, and organizations in 2024
- Key themes to consider in developing and maintaining your privacy program
Goodbye Windows 11: Make Way for Nitrux Linux 3.5.0!SOFTTECHHUB
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2. ACS Catalysis
Review
Table 1. Nitrogen-Doping Methods and Nitrogen Concentration on Graphene
no.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
synthesis
method
CVD
CVD
CVD
CVD
CVD
segregation
growth
solvothermal
arc discharge
thermal
treatment
thermal
treatment
thermal
treatment
thermal
treatment
thermal
treatment
thermal
treatment
plasma
treatment
plasma
treatment
plasma
treatment
plasma
treatment
plasma
treatment
N2H4
treatment
N2H4
treatment
precursors
application/
reference
N content, at. %
Cu film on Si substrate as catalyst, CH4/NH3
Cu foil as catalyst, NH3/He
Ni film on SiO2/Si substrate as catalyst, NH3/CH4/H2/Ar (10:50:65:200)
Cu foil as catalyst, acetonitrile
Cu foil as catalyst, pyridine
carbon-contained Ni layer on nitrogen-contained boron layer
1.2−8.9
1.6−16
4
∼9
∼2.4
0.3−2.9
FET30
ORR40
ORR41
lithium battery43
FET44
FET50
Li3N/CCl4 (NG1) or N3C3Cl3/Li3N/CCl4 (NG2)
graphite/H2/He/pyridine (NG1) graphite/H2/He/NH3 (NG2) transformation of
nanodiamond/He/pyridine (NG3)
N+ ion-irradiated graphene, NH3
4.5 (NG1) or 16.4 (NG2)
0.6 (NG1), 1 (NG2), 1.4
(NG3)
1.1
ORR52
56, 57
graphite oxide after thermal expansion, NH3/Ar
2.0−2.8
ORR60
FET59
FET31
GNR, NH3
GO, NH3/Ar (10% NH3)
∼3−5
FET63
GO, NH3
6.7−10.78
GO, melamine
7.1−10.1
methanol
oxidation73
ORR62
graphite oxide after thermal expansion, N2 plasma
8.5
ORR23
graphite oxide after thermal expansion, N2 plasma
3
ORR67
chemically synthesized graphene, N2 plasma
∼1.3
biosensors68
GO, treat with H2 plasma first, then treat with N2 plasma
1.68−2.51
ultracapacitor69
FET70
mechanically exfoliated graphene or bilayer graphene grown by CVD, NH3 plasma
GO, N2H4, NH3
4.01−5.21
71
graphite oxide after thermal expansion, N2H4
1.04
electrochemical
sensor72
have the potential to create a homogeneous doping throughout
the bulk material, the results reported so far fail to indicate so.
Specifically, direct synthesis includes chemical vapor deposition
(CVD), segregation growth, solvothermal, and arc-discharge
approaches. Post treatment includes thermal treatment, plasma
treatment, and N2H4 treatment. Table 1 gives a summary of
various methods used for the synthesis of N-graphene. Detailed
discussion on these methods is elaborated below.
2.1. Direct Synthesis. 2.1.1. CVD Approach. CVD is a
widely used method to synthesize various carbon nanomaterials, such as graphene,36 CNTs,37 carbon nanofibers,38 and Ndoped CNTs.39 Recently, it was successfully applied to prepare
N-graphene. Typically,30,40,41 a metal catalyst (Cu or Ni) is
used as the substrate, then at high temperature, a carbon source
gas mixed with a nitrogen-containing gas is introduced. These
precursors dissociate and recombine into N-graphene by means
of precipitation on the surface of the catalyst.30,42
Apart from the gas mixture, liquid organic precursors
(acetonitrile, pyridine) have also been used to form Ngraphene.43,44 Theoretical study about different precursors45
shows that proper skeletal bonds of liquid precursors are crucial
for the formation of N-graphene. Acrylonitrile containing the
C−C single bond, CC double bond, and CN triple bond
cannot form N-graphene, but pyridine with only the double
bond forms N-graphene. The proposed reason is that the single
bond is easy to break, even at low temperature, leaving CC
and CN bonds at the catalyst surface. Then CN bond is
reduction reaction (ORR), or anchor the metal nanoparticles
used in the catalytic reaction. Moreover, after nitrogen doping
in the monolayer graphene, the Fermi level shifts above the
Dirac point,27,28 and the density of state near the Fermi level is
suppressed;29,30 thus, the band gap between the conduction
band and the valence band will be opened. For GNRs, the band
gap is still kept after doping.31 The band gap in N-graphene
makes it a candidate to be used in semiconductor devices. Apart
from these, N-graphene can also be used in batteries, sensors,
and ultracapacitors. The nitrogen doping of graphene greatly
broadens its applications.
Previously, several reviews on graphene have mentioned Ngraphene,32−35 especially the review of Liu et al.,35 which
focused on two chemical doping approaches and band gap
tuning; however, there is still no systematical study of Ngraphene synthesized by substitutional doping. Therefore, in
this review, we summarize different synthesis and characterization methods of nitrogen-substituted graphene; the
application of N-graphene is also reviewed on the basis of
experimental and theoretical studies.
2. SYNTHESIS OF N-GRAPHENE
Similar to the synthesis of N-CNT, N-graphene can be
obtained through two different ways: direct synthesis and
post treatment. Most postsynthesis treatments may lead to
surface doping only. Although in principle, direct synthesis may
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Figure 2. Schematic illustration of the segregation technique for growing N-doped graphene.50
2.1.3. Solvothermal Approach. The solvothermal approach
was first employed for gram-scale production of graphene.51
Recently, gram-scale production of N-graphene has been
achieved by applying this approach at ∼300 °C. By mixing
lithium nitride (Li3N) with tetrachloromethane (CCl4) (Figure
3) or cyanuric chloride (N3C3Cl3) with Li3N and CCl4, N-
preferentially removed from the surface by forming volatile
molecules when the temperature is higher than 400 °C; thus,
only CC will be left to form nondoped graphene above 500
°C. In contrast, the skeletal bonds in pyridine have similar bond
energies, which induces the formation of N-graphene.
The layer distribution of N-graphene is varied in different
studies. Although the N-graphene synthesized from the gas
mixture C2H4/NH3 is claimed to be monolayer through the
analysis of Raman spectroscopy,40 N-graphene synthesized
from a gas mixture, CH4/NH3,30,41 shows that the few-layer
graphene is predominant after high-resolution transmission
electron microscope (HRTEM) characterization. In other
studies, monolayer N-graphene is also obtained when
acetonitrile43 or pyridine44 is used as precursors. Furthermore,
the layer of N-graphene can be adjusted by the flowing time if
acetonitrile is used as the precursor.43
In the CVD approach, the nitrogen content can be controlled
by changing the flow rate40 and the ratio between carbon
source and nitrogen source.30 It has been reported30 that the
doping level decreased from 8.9 to 3.2 or 1.2 at. % if the NH3/
CH4 ratio was lowered from 1:1 to 1:2 or 1:4, respectively.
Moreover, although high nitrogen content (∼16 at. %) has
been reported,40 the nitrogen content in this method is
normally around 4−9 at. %.
The bonding configuration of nitrogen within N-graphene
varies with different studies. By using Cu as the catalyst and
CH4/NH3 (1:1) as the precursor, the nitrogen type in Ngraphene is mainly quaternary N;30 however, when Ni is used
as the catalyst and CH4/NH3 (5:1) is used as the precursor, the
obtained N-graphene consists of mainly pyridinic N and
pyrrolic N.41 If C2H4/NH3 is used as the precursor while
keeping Cu as the catalyst, the pyridinic N becomes the
predominant type.40 Notably, the syntheses of other nitrogendoped carbon materials have revealed that the doping
environment is also influenced by the flow rate, catalyst, and
growth temperature,46−49 so further research is required to
clarify the relationship between the bonding configuration of
nitrogen and the parameters of CVD.
2.1.2. Segregation Growth Approach. In this approach, a
nitrogen-containing boron layers and carbon-containing nickel
layers are sequentially deposited on the SiO2/Si substrate by
electron beam evaporation, then during the vacuum annealing
process, the boron atoms are trapped by nickel, and the carbon
atoms will segregate out onto the nickel surface and combine to
form N-graphene (Figure 2).50 Although sporadic multilayer
areas are observed, the N-graphene generally shows a largescale, uniform, and few-layer structure. The nitrogen content
(0.3−2.9 at. %) can be controlled by adjusting the thickness of
the boron and nickel films. The pyridinic and pyrrolic N are
dominant in N-graphene. Interestingly, the graphene can be
doped in a specific area by embedding nitrogen species into the
selective area of the substrate.
Figure 3. Schematic illustration for N-graphene synthesized from the
reaction of CCl4 and Li3N.52
graphene with different nitrogen contents was obtained
(denoted as NG1 and NG2, respectively).52 The HRTEM
images of N-graphene show that it mainly consists of 1−6 layer
graphene. Because of the introduction of N3C3Cl3, NG2 has a
higher nitrogen content (16.4 at. %) compared with NG1(4.5
at. %). The proportion of doped nitrogen species also changes
with different reactant mixtures. The quaternary N dominates
in NG1, and pyridinic and pyrrolic N dominates in NG2.
2.1.4. Arc-Discharge Approach. An arc-discharge approach
has been applied to obtain CNTs and doped CNTs by
evaporating the carbon source, normally graphite,53−55 at high
temperature. Rao et al.56,57 successfully obtained N-graphene
by applying this method in the presence of pyridine vapor or
NH3. The N-graphene synthesized from transformation of
nanodiamond shows higher nitrogen content than that
synthesized from graphite. The nitrogen content of the assynthesized N-graphene is around 0.5−1.5 at. %. Moreover,
although single layer N-graphene is occasionally observed, most
of the N-graphene possesses two or three layers. The scale of
graphene and N-graphene produced by this method normally is
below 1 μm.56,58
2.2. Postsynthesis Treatment. 2.2.1. Thermal Treatment. Thermal treatment refers to the method using high
temperature to produce N-graphene. It has been shown that
heating graphene in NH3 at high temperature (≥800 °C) can
produce N-graphene.59,60 Electrical annealing, which produces
high temperature, has also been applied to obtain N-GNRs.31
The nitrogen content in the N-graphene synthesized by this
method is relatively low. Guo et al.59 obtained N-graphene with
1.1 at. % doping level at 1100 °C; Geng et al.60 reported that
the highest nitrogen content was 2.8 at. % at 800 and 900 °C.
The low doping level may be attributed to two reasons: one is
the insufficient defect number in the high quality graphene, and
the other is the high annealing temperature, which will break
the C−N bonds in N-graphene.61 Moreover, the nitrogen
doping is more likely to occur at the defects and edge of
graphene in the thermal treatment method. Geng et al.60 found
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temperature is 80 °C; however, the absorbed N2H4 takes a nonnegligible proportion in the total nitrogen content. If the
reaction temperature rises to 160 °C or higher, the N2H4 will
be desorbed and the nitrogen content decreases to ∼4 at. %.
Interestingly, the morphology of N-graphene also changes with
the temperature. The relative flat N-graphene is generated if
GO is reduced at low temperature (≤120 °C), whereas the
obvious agglomeration in N-graphene will occur if the
temperature is higher.
By using ultrasonication,72 N-graphene can be synthesized
from graphene in the presence of N2H4. The agglomerated
regions are also observed after doping. The nitrogen content is
around 1 at. %. In addition to these, the nitrogen species in the
N-graphene contains only pyridinic and pyrrolic nitrogen. The
content and bonding configuration of nitrogen indicates the
nitrogen atoms can be introduced only to the graphene edges
and defects in this method.
pyridinic and pyrrolic N dominated in the N-graphene. Wang
et al.31 claimed that nitrogen atoms preferred functionalizing
the edge of GNRs. Interestingly, unlike NH3, annealing N+ ion
irradiated graphene in N2 at high temperature cannot introduce
nitrogen into the graphene,59 which suggests that the inertness
of N2 makes it difficult to react with the reactive carbon atoms
on the defect sites in graphene.
Apart from graphene, graphene oxide can also be used to
synthesize N-graphene by thermal treatment in the presence of
various nitrogen precursors. Sheng et al.62 reported that
annealing GO in the presence of melamine at high temperature
(700−1000 °C) could produce N-graphene. The layer
distribution of N-graphene depends on the synthesis procedure.
Few-layer N-graphene is obtained if annealing the mixture of
GO and melamine at high temperature, and single layer Ngraphene can be produced if heating single-layer GO covered
with melamine. The nitrogen content is affected by both the
temperature and the mass ratio between GO and melamine.
The largest nitrogen content (10.1 at. %) is obtained under 700
°C when the mass ratio of GO to melamine is 0.2. Li et al.63
showed that placing GO in an NH3 atmosphere through
thermal annealing (500 °C) could reduce GO and get Ngraphene with a 5 at. % nitrogen doping level. Notably, both of
these works report that the temperature has the major influence
on the nitrogen content of N-graphene. Li et al.63 ascribed the
reason to the decreased content of oxygen functional groups at
higher temperature. Because these oxygen functional groups are
responsible for the formation of a C−N bond, the reactivity
between GO and nitrogen atoms will decrease after these
groups decompose at higher temperature, resulting in the lower
nitrogen content. Moreover, it has been claimed that lowering
the mass ratio between GO and melamine at 800 °C induced
higher nitrogen doping level, which may suggest the
competitive doping between oxygen and melamine.62
2.2.2. Plasma Treatment. When carbon material is placed in
the nitrogen plasma atmosphere, carbon atoms will be partly
replaced by nitrogen atoms; therefore, this method was applied
to synthesize N-CNTs.64−66 Recently, it has been reported that
N-graphene could be prepared from graphene23,67,68 or GO69
by exposing it to the nitrogen plasma. NH3 plasma has also
been used to obtain N-graphene from mechanically exfoliated
graphene .70 The nitrogen content, which can be controlled by
the plasma strength and exposure time, varies from 3 to 8.5 at.
% in different works. During the plasma exposure process,
defects and oxygen-containing groups are created.23,68 Shao et
al.23 showed that graphene contains 3.5 at. % oxygen species
while the N-graphene contains 8.6 at. % oxygen species, Wang
et al.68 reported that the content of oxygen species increased
from about 15 to 26−28 at. % after doping. These results
indicate the plasma treatment introduces a significant amount
of oxygen species into graphene. The reason may be ascribed to
the reactive carbon atoms at the edge of defects that are created
by the plasma treatment.23 Notably, in the N2 plasma
treatment, overexposure may decrease the electrocatalytic
activity of N-graphene.68 It has been reported that if graphene
was exposed to the N2 plasma over 40 min, the reduction
current of H2O2 would decrease because of the destruction and
split of the graphene plane.
2.2.3. Hydrazine Hydrate (N2H4) Treatment. Using
hydrazine hydrate to prepare graphene from GO is a widely
used method. Recently, N-graphene has been obtained by
reducing GO in the NH3 and N2H4 mixed solution.71 The
nitrogen content reaches up to 5 at. % when the reduction
3. CHARACTERIZATION TECHNIQUES FOR STUDYING
NITROGEN-DOPED GRAPHENE
3.1. X-ray Photoelectron Spectroscopy (XPS) Technique. XPS is the standard technique to study the nitrogendoping effect in graphene. In the XPS spectrum of N-graphene,
the peaks appearing at about 400 and 284 eV correspond to the
N1s and C1s, respectively. The ratio of peak intensity between
N1s and C1s is used to determine the nitrogen content in Ngraphene. Moreover, the N1s spectrum is used to determine
the nitrogen configurations. In the research about N-graphene,
the N1s spectrum usually can be deconvoluted to several
individual peaks that are assigned to pyridinic N (398.1−399.3
eV), pyrrolic N (399.8−401.2 eV), and quaternary N (401.1−
402.7 eV) (Figure 4). The peak position of these nitrogen types
Figure 4. High-resolution N1s XPS spectra of graphene and Ngraphene. N1 represents pyridinic N, N2 represents pyrrolic N, N3
represents quaternary N, and N4 represents the N oxides of pyridinic
N.23
varies in a relatively wide range in different studies. Reddy et
al.43 reported the pyrrolic N appeared at 401.2 eV, whereas Li
et al.63 showed the quaternary N appeared at about 401.1 eV.
The large difference of the peak positions of nitrogen
configurations may be due to the different environments of
nitrogen.19 The charge of nitrogen and its neighbor atoms and
the electron redistribution after ionization will all influence the
precise position of different nitrogen types. Apart from these
three nitrogen types, peak corresponding to N-oxides of
pyridinic N is observed at ∼402.8 eV in several studies.23,62
When nitrogen atoms are doped into graphene, peaks at the
C1s spectrum will change accordingly.50,62,63,70,71 In the C1s
spectrum of GO (Figure 5a), the sharp peak at around 284.5 eV
corresponds to the sp2 carbon with CC bonds. Another
strong peak at higher energy corresponds to the sp3 carbon
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Figure 5. High-resolution C1 spectra of the (a) GO, (b) graphene prepared by annealing GO in Ar at 800 °C, and (c) N-graphene prepared by
annealing GO/melamine (1:5) at 800 °C for 30 min.62
and one defect for the D mode. Different from the D band
which requires defects to activate it, the 2D band does not
require the activation of defects. Thus, the 2D band is always
seen in the Raman spectra of graphene and N-graphene, even
when the D band cannot be observed. For the D′ band, it arises
from the intravalley, defect-induced, double-resonance process.
Previous studies77,79 have revealed that the intensity ratio of
the D and G bands (ID/IG) was inversely proportional to the inplane crystallite sizes La. The crystallite size can be determined
according to the Tuinstra−Koenig (TK) relation, La(nm) =
(2.4 × 10−10) λ4(ID/IG)−1 (λ is the Raman excitation
wavelength). For nitrogen doping, the substitution of nitrogen
atoms usually is accompanied by the introduction of defects
into the graphene surface. Considering La as the average
interdefect distance, more defects undoubtedly means a smaller
La; thus, La can be used to study defects introduced by nitrogen
doping. Comparing the crystallite size of pristine graphene with
N-graphene, Zhang et al.50 reported that the ID/IG of graphene
and N-graphene with lower (NG1) and higher (NG2) nitrogen
doping level are 0.26, 0.8 and 2.1, which corresponds to
crystallite sizes of 65, 21, and 8 nm, respectively (Figure 7).
with several different C−O bonding configurations. These
configurations include the C−O bonds, carbonyls (CO), and
carboxylates (OC−O) at about 286.2, 287.8, and 289.2 eV,
respectively. After GO is annealed in Ar, the intensity of the
peak ascribed to the C−O bonding configurations decreases to
a much lower value (Figure 5b).62 This indicates that most of
the oxygen groups in GO are removed after annealing. If GO is
doped with nitrogen atoms (Figure 5c), peaks ascribed to C−O
bonding configurations disappear, and new small peaks appear
after peak fitting.50,62,70,71 In the work of Sheng et al.,62 new
peaks appearing at 285.8 and 287.5 eV were assigned to the sp2
and sp3 carbon atoms, respectively. In other works,50,70 a new
small peak at ∼289 eV was observed. This peak is ascribed to
the physisorbed oxygen on the graphene. Generally speaking,
the peak change at higher energy in the C1s spectrum suggests
the nitrogen doping occurs in the graphene.
3.2. Raman Spectroscopy. Raman spectroscopy is another
very useful method to characterize N-graphene. The D, G, and
2D bands are the predominant features in the spectrum of Ngraphene. They are represented by peaks at around 1320−
1350, 1570−1585, and 2640−2680 cm−1, respectively (Figure
6.) In some studies,40,52 the peak called D′ will appear at
Figure 7. Raman spectra of pristine graphene and N-graphene with 0.6
(NG1) and 2.9 (NG2) at. % doping level. The insert shows the
enlarged 2D band of NG2. The laser excitation wavelength is 514.5
nm.50
This suggests the crystallite size decreases remarkably with an
increase in the nitrogen doping level because of the defects.
Apart from ID/IG, the intensity ratio of the 2D and G bands
(I2D/IG) has been used to characterize N-graphene. It has been
reported that I2D/IG depends on the electron concentration
(Figure 8).80 The G band always stiffens, and the 2D band
responds differently to hole and electron doping; thus, I2D/IG
has been used to estimate the nitrogen doping level.50,70
Through calculating the I2D/IG, which was <0.6 in N-graphene,
it was concluded that the doping level was higher than 4 × 1013
cm−2.50 Notably, some studies also presented that the G band
increased almost linearly, corresponding to the increment of
Figure 6. Typical Raman spectrum of N-graphene transferred onto a
SiO2/Si substrate. The laser excitation wavelength is 514.5 nm.44
∼1602−1625 cm−1. These bands already have been studied
intensively in former studies.74−78 Specifically, the G band
corresponds to the doubly degenerate E2g phonons at the
Brillouin zone. It originates from the first-order Raman
scattering process. The 2D and D bands are all induced by
the second-order, double-resonance process and related to
zone-boundary phonons. The scattering process involves two
zone-boundary phonons for 2D mode; it involves one phonon
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indicates the purple paths are related to the local dopant
concentration.
Some studies reported a shift of the G band after nitrogen
doping. Because the variation of charge density in pristine
graphene will cause the different G band positions and I2D/IG in
the different spots of graphene,85 Li et al. made a gold marker
in the vicinity of graphene to accurately monitor the evolution
of the nitrogen doping.70 An upshift of the G band in the
Raman spectra of the monolayer graphene was observed. In the
work of Zhao et al.,84 a similar trend of the G band was also
observed by using the frequency histogram collected from
Raman spectral mapping (Figure 9d). However, the observed
position of the G band can also be affected by the
inhomogeneous layer distribution82,86 and defects due to
nitrogen doping,87 which may induce the downshift of G
band in N-graphene in some studies.52,63 Thus, comprehensive
consideration should be taken if discussing this phenomenon.
3.3. Scanning Tunneling Microscopy (STM). STM is a
very powerful technique to investigate the electronic properties
of a sample. It can probe the charge density at the Fermi level.
When the bias voltage (Vbias) applied between the tip and
sample is positive, electrons tunnel from the tip into the
specimen, then the lowest unoccupied states of the specimen
are probed. When a negative Vbias is applied, electrons tunnel
from the specimen into the tip, and the highest occupied states
of specimen are probed.88 Due to the sharp tip, the STM
images can show atomic resolution. Recently, both theoretical
and experimental studies on the electronic properties of Ngraphene have been carried out.52,84,89
Compared with the pristine graphene, N-graphene shows
some brighter sections that are distinct from the main graphene
network in the STM image (Figure 10c).52,84 Different bright
features correspond to different nitrogen doping types. Because
these bright sections are only a few atoms across (<1 nm), they
cannot be defects induced by nitrogen doping.52 Through the
STM line scan over the bright section and graphene lattice
(Figure 10a), an out-of-plane height of 0.6 ± 0.2 Å is observed.
This indicates the substitution of nitrogen atoms in graphene.
The calculated STM image shows that the C atoms neighboring
Figure 8. The influence of hole and electron doping on the I2D/IG.80
graphene layers,81 and IG/I2D was related to the thickness of the
graphene.82,83 Thus, for N-graphene with inhomogeneous
layers, the I2D/IG cannot reflect the nitrogen doping level.
I2D/IG can be used only when N-graphene has homogeneous
layers.
Before using ID/IG and I2D/IG to characterize N-graphene,
inhomogeneous nitrogen doping should be considered. It has
been reported that some spots showed high ID/IG and some
showed very low ID/IG within the N-graphene,40 which suggests
the nonuniform defect distribution induced by inhomogeneous
nitrogen incorporation. Thus, the ID/IG and I2D/IG derived
from the Raman spectra at discrete spots cannot fully reflect the
doping situation. In practice, Raman spectral mapping can be
used to avoid this problem. This technique records the Raman
spectra on a large scale; thus, the comparison of different Ngraphenes is more convincing for inhomogeneous doping. In
the maps of I2D/IG over a 80 × 80 μm2 area (Figure 9b),84 the
pristine graphene shows a higher I2D/IG, which means a lower
carrier concentration. The more area of low I2D/IG in Ngraphene grown under higher NH3 ratio corresponds to a
higher carrier concentration. Moreover, it is observed that the
size of the purple paths depends on the doping level, which
Figure 9. (a) Raman spectra taken at different positions over N-graphene grown under 0.1 Torr NH3 (NG10). (b) Maps of I2D/IG for pristine
graphene, NG10, and N-graphene grown under 0.13 Torr NH3 (NG13). (c) Maps of the G band frequency for PG, NG10, and NG13 samples. (d)
G band frequency histogram of PG, NG10, and NG13 from the maps in part c.84
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Figure 10. (a) STM image of the most common doping form in N-graphene. The inset is the line profile across the dopant (Vbias = 0.8 V, Iset = 0.8
nA). (b) Simulated STM image of quaternary N dopant based on density functional theory calculations (Vbias = 0.5 V). (c) STM image of Ngraphene showing ∼14 quaternary N dopants. The inset is the FFT of topography (Vbias = 0.8 V, Iset = 0.8 nA). (d) Spatial distribution of N−N
distances from eight samples with different nitrogen concentrations. (e) dI/dV curves taken from an N atom and other nearby bright topographic
features (Vbias = 0.8 V, Iset = 1.0 nA).84
4. APPLICATIONS
4.1. Electrocatalyst for Fuel Cell Application. A fuel cell
is an electrochemical energy conversion device that oxidizes
fuel at the anode and reduces oxygen from air at the cathode to
produce electricity.90 Commonly, Pt is used as the catalyst for
the oxidation reaction on the anode and reduction reaction on
cathode. However, the commercial application of Pt catalysts is
limited by its scarcity, time-dependent drift, and CO poisoning.90 Thus, Pt-based catalysts91,92 and other metal catalysts,
such as Au and Pd,93,94 have been developed. Recently, Ngraphene has been used in fuel cells as either the catalysts
directly or carbon support to anchor metal catalysts.
4.1.1. Theoretical Part. The oxygen reduction reaction of Ngraphene on the cathode of a fuel cell has been discussed in
many studies. Through studying the ORR behavior of model
graphenes C45NH20 and C45NH18 in acidic environment, Zhang
et al.25 showed that the spin density and charge density of
atoms were the major factors that determined the catalytic
active sites in ORR. The substitution of N atoms, which
introduces the unpaired electron, will change the atomic charge
distribution. The active sites in N-graphene usually are carbon
atoms that possess high spin density. If the spin density is
negative and small, the atom with a higher charge density will
be the active sites. Although in a previous study,95 it was shown
that the energy gap between highest occupied molecular orbital
(HOMO) and lowest unoccupied molecular orbital (LUMO)
could be used as an index of kinetic stability, it is unnecessarily
related to the catalytic capacity of graphene and N-graphene.
The ORR mechanism on N-graphene also has been studied.
Earlier studies have shown that O2 could be reduced following
two pathways. One is a direct four-electron pathway in which
O2 is reduced to water in an acidic environment or OH− in an
alkaline environment. Another is a two-electron pathway in
which O2 is partly reduced to H2O2 in an acidic environment or
OOH− in an alkaline environment. Both mechanisms have
been proposed by theoretical studies based on different Ngraphene models. Kurak et al.96 showed a two-electron ORR
pathway based on the graphene model possessing two neighbor
N atoms exhibit the brightest feature because of the increased
charge density of state induced by the neighbor N atoms
(Figure 10b).52,84
Apart from the local structure around dopants, some long
“tails” arising from the intervalley electron scattering are
observed in the STM image (Figure 10c). This kind of
scattering is verified by the inner hexagon in the fast Fourier
transform (FFT). STM is also used to study the possibility of
dopant clustering. The dopant distribution in the N−N
distance is quadratic even when the distance is down to few
lattice constants (Figure 10d); it indicates that the dopants
distribute randomly. Furthermore, the study reveals that nearby
dopants prefer to substitute into the same sublattice of
graphene. The charge-carrier density of N-graphene can be
measured from a STM study. From the curves of dI/dV
(derivative of current with respect to the voltage), the Dirac
point of N-graphene is calculated (Figure 10e). Then the
charge-carrier density can be calculated from the relation n =
ED2/π(h̅vF)2 (n is the charge-carrier density, h̅ is the Plank’s
constant over 2π, νF is the Fermi velocity).
3.4. Other Characterization Techniques. In addition to
the above techniques, scanning electron microscope (SEM),
HRTEM, atomic force microscope (AFM), selected area
electron diffraction (SAED) and thermogravimetric analysis
(TGA) have also been used to study N-graphene. Specifically,
SEM is commonly employed to study the morphology of Ngraphene. HRTEM is the most commonly used technique to
determine the number of graphene layers on the basis of the
cross section or edge images of N-graphene. AFM can also be
used to estimate the number of graphene layers on the basis of
the interlayer distance. SAED can provide information about
the crystalline structure of N-graphene on the basis of
diffraction pattern. The hexagonal diffraction spots indicate
that the N-graphene still keeps a well-ordered crystalline
structure,44,62 and the ringlike diffraction pattern of spots
means structure distortion occurs after doping.41
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N atoms in the zigzag edge. However, it was found that two
nitrogen atoms were very unlikely to be doped at two
neighboring zigzag sites by checking the interaction energy
between two nitrogen atoms.97
Zhang et al.25 proposed a four-electron ORR pathway on Ngraphene in an acidic environment. Furthermore, after taking
the solvent, surface coverage, and adsorbates into consideration,
Yu et al.98 obtained the overall energy profile of the ORR
pathway on N-graphene in an alkaline environment. The study
shows that water molecules are essential for the reaction. The
O2 adsorption is greatly enhanced due to the O2 polarization
induced by the hydrogen bonding with water. Through
investigating two ORR mechanisms, dissociative and associative
(Figure 11), study shows that the associative mechanism is
Figure 11. Scheme of the ORR reaction on N-graphene in an alkaline
environment where 1 is the associative mechanism and 2 is the
dissociative mechanism.98
Figure 12. (a) RRDE voltammograms for ORR in air-saturated 0.1 M
KOH on the electrodes graphene (red), Pt/C (green), and Ngraphene (blue) with a scan rate of 0.01 V s−1. Electrode rotating rate:
1000 rpm. (b) Current−time chronoamperometric response of Pt/C
and NG to CO. The arrow indicates the addition of 10% (v/v) CO at
−0.4 V.41
more energetically favored in ORR because of the lower O2
dissociation barrier. In the associative mechanism, the
desorption barrier of OOH(ads) into OOH− is high, so the
energetically favored reaction OOH(ads) → O(ads) + OH− is
more likely to happen, which suggests the four-electron ORR
pathway of N-graphene. The reaction rate is determined by the
removal of O(ads) on the surface of N-graphene.
Apart from N-graphene, the interaction between Pt atom and
N-graphene has been investigated.26 In N-graphene, the
nitrogen atoms do not bond with Pt atom directly; instead,
they direct a Pt atom to bond with the carbon atom, which is
more energetically favored. This is helpful to prevent Pt
nanoclusters from migrating and forming larger particles.
Because the introduction of nitrogen atoms disrupts the
delocalized double bond in the graphene system, the Pt/C
bond will focus on the 6s/2s orbitals rather than 5d/2p orbitals.
This doubles the binding energy between Pt and carbon atoms.
In general, the binding of Pt to N-graphene improves the
catalytic durability of Pt.
4.1.2. Experimental Part. Several groups have recently
reported studies on metal-free N-graphene with enhanced
catalytic activity toward ORR.23,40,41,52,60,62 The efficiency of
ORR can be evaluated through two ways.99 One way is to
calculate the transfer number of electrons through the
Koutecky−Levich (K−L) equation by using a rotating disk
electrode (RDE). Another way is to measure the proportion of
H2O2 formed during the ORR process by using a rotating ringdisk electrode. Qu et al.41 reported that N-graphene exhibited a
typical one-step, four-electron ORR pathway, which is similar
to the ORR pathway of a Pt catalyst (Figure 12a). In contrast,
pristine graphene showed a two-step, two-electron ORR
pathway with a lower onset potential. In another work,60 the
H2O2 formed in the ORR process was about 10% at −0.5 V in
the diffusion-controlled region. The low proportion of H2O2
indicated the four electron reduction process dominated in
ORR. All these studies show that N-graphene can be a very
effective catalyst for ORR.
Furthermore, the ORR activity of N-graphene is also studied
through diffusion limited current and kinetic current. Some
studies showed the diffusion-limited current density of Ngraphene was higher than commercial 20% or 40% Pt/C (ETEK) catalyst,41,52 but another study showed that N-graphene
had a similar diffusion-limited current density.60 Although the
reported activity of N-graphene varies from different studies,
there is consensus that N-graphene has excellent stability
compared with the Pt catalyst. Shao et al.23 reported that the
20% Pt/C (E-TEK) showed higher electrocatalytic activity than
N-graphene before an accelerated degradation test (ADT), but
after the ADT, the N-graphene exhibited higher kinetic current
compared with the Pt/C catalyst because of the degradation of
Pt/C. In addition, studies also showed the activity of Ngraphene would not be influenced by the addition of methanol
or CO (Figure 12b).23,41 These two advantages make Ngraphene a promising material toward ORR in fuel cells.
Notably, in the above studies in which the four-electron ORR
pathway was observed, these N-graphene catalysts consist of
two or three nitrogen types.23,41,52,60,62 For N-graphene
possessing only the pyridinic N, a two-electron reduction
process was observed in the ORR process.40 This may indicate
a less efficient ORR performance of pyridinic N. In another
study, the N-graphene with higher pyridinic and quaternary N
content exhibited a higher onset potential than N-graphene that
possessed the same nitrogen content. This suggests the
pyridinic and quaternary N may play a more important role
for ORR activity.60 However, because of the scarcity of study in
this field and variation in experimental conditions, the
relationship between the catalytic activity and the nitrogen
species is still unclear. In the former study of N-CNTs, both
quaternary100,101 and pyridinic21,24 nitrogen have been
observed to have the dominant effect for the ORR activity.
Thus, further research work on the nitrogen catalytic site is still
required.
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Figure 13. (a) Cyclic voltammetry (CV) of Co3O4/rmGO, Co3O4/N-rmGO and Pt/C in O2- (solid line) or Ar-saturated (dashed line) 0.1 M KOH
solution. RDE voltammograms of Co3O4/rmGO (b) and Co3O4/N-rmGO (c) for ORR in O2-saturated 0.1 M KOH at different rotation rates with a
scan rate of 5 mV s−1. The inset figure is the corresponding Koutecky−Levich plots at different potentials. (d) Tafel plots of Co3O4/rmGO and
Co3O4/N-rmGO derived by the mass-transport correction.104
impregnating N-graphene into a mixture of iron acetate and
1,10-phenanthroline, then the FexC species formed in the
sintering process would anchor the FeCN nanoparticles on Ngraphene surface. The as-synthesized FeCN/N-graphene shows
an enhanced ORR activity compared with the N-graphene
because of the additional ORR activity of FeCN nanoparticles.
In another notable study,104 Liang et al. grew Co3O4 on mildly
oxidized graphene oxide (rmGO) with or without the presence
of NH4OH, then catalyst Co3O4/rmGO and Co3O4/N-rmGO
were obtained. The latter catalyst has ∼4 at. % nitrogen
content. Through the ORR study of the Co3O4/rmGO and
Co3O4/N-rmGO, it has been revealed that these two catalysts
exhibit high ORR activity that is different from the Co3O4
nanocrystals (Figure 13a). Also different from the two-electron
ORR pathway of N-rmGO obtained in the study, these two
catalysts show the obvious four-electron ORR pathway (Figure
13b, c). Comparing the kinetic current of Co3O4/N-rmGO
with Co3O4/rmGO, the former exhibits the apparent higher
current density than the latter (Figure 13d). The higher ORR
activity of Co3O4/N-rmGO is ascribed to the synergistic
coupling between Co3O4 and N-graphene. Because Co3O4/NrmGO shows both the high ORR activity similar to Pt catalyst
and excellent stability, this kind of hybrid catalyst is also
promising for ORR catalysis.
4.2. Field-Effect Transistor (FET). For semiconductors,
the flow of electricity needs some kind of activation (for
example, heat or light absorption) to get over the gap between
the valence band and conduction band.105 If the semiconductor
is activated by the external electric field to switch “on” and “off”,
then it is called FET. Generally speaking, the large-scale and
Apart from the nitrogen types, the nitrogen content is also
related to the ORR activity of N-graphene. However, because
N-graphene usually consists of two or three nitrogen types and
the content of different nitrogen types usually varies with
different nitrogen doping levels, different studies have produced
contradictory results in previous studies.52,62 In a more direct
study in which N-graphene contains only pyridinic N,40 the Ngraphene possessing the higher nitrogen content (16 at. %)
exhibited poorer ORR activity than that possessing the lower
nitrogen content (2.2 at. %). In a theoretical study, it has been
reported that model graphene with a higher nitrogen content
was more easily poisoned by O(ads) because of the stronger
affinity.102 These results mean an optimal nitrogen content
might be critical to achieving a high ORR activity.
Several studies also have studied the performance of Pt/Ngraphene in both oxidation and reduction reactions.67,73 For
Pt/N-graphene used for an oxidation reaction,73 it has been
reported that Pt nanoparticles could disperse better on the
surface of N-graphene with the existence of N atoms in a
carbon lattice. Moreover, the conductivity of N-graphene was
improved at high temperature (800 °C). These two factors
made Pt/N-graphene exhibit a 3 times higher oxidation current
than 20% Pt/carbon black catalyst. For Pt/N-graphene used for
the oxygen reduction reaction,67 it also showed an improved
performance compared with Pt/graphene because of the better
dispersion of Pt nanoparticles and stronger interaction between
Pt and C atoms stated in the theoretical part.26
Apart from the Pt catalyst, other nonprecious metal catalysts
supported on N-graphene toward ORR have been studied.103,104 Tsai et al.103 synthesized FeCN/N-graphene by
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Kubo-Greenwood approach.27 When the nitrogen concentration (Cd) is over or equal to 2% (2% ≤ Cd ≤ 4%), the decay
of the diffusion coefficient D is clearly observed. This indicates
the onset of quantum interference effects. However, this effect
is still weak and can only marginally affect the conduction when
the nitrogen content is low. This study suggests that the
nitrogen doping may modulate the graphene property while
maintaining good mobility and conductivity. However, the
conduction is also influenced by many other factors. In
experimental study, it has been shown that both defects and
nitrogen atoms will be introduced into graphene. Defects can
serve as the scattering center, which will affect the mobility of
N-graphene. Moreover, when the nitrogen concentration rises
over 5%, a stronger localization effect might occur, which will
largely decrease the mobility in N-graphene.27
GNR can be obtained by constraining large-scale graphene to
one dimension. Former studies have revealed that Hterminated GNRs with either armchair or zigzag-shaped
edges have nonzero band gaps.7,9,108 Through theoretical
studies of zigzag GNR (ZGNR),109,110 it was revealed that the
nitrogen atom and defects energetically preferred to dope at the
edge of GNR. Depending on doping sites and various GNRs,
the introduction of nitrogen atoms will induce very different
electronic properties. For example, Yu et al.109 showed different
nitrogen doping sites would make the impurity state lie below
or above the Fermi level. Li et al.110 found one edge-doped
nitrogen made ZGNR spin a gapless semiconductor while two
opposite edge-doped nitrogens made ZGNR nonmagnetic
metals. Biel et al.111 reported that the full suppression of
impurity backscattering would occur if the doped GNR was
armchair and mirror-symmetrical.
4.2.2. Experimental Part. After the preparation of bottomgated N-graphene FET by using a Si substrate with a 500 nm
thick SiO2 layer (Figure 15a), pristine graphene exhibits p-type
behavior because of the adsorption of oxygen or water in air
(Figure 15b). In contrast, N-graphene with a 8.9 at. % nitrogen
bilayer graphene do not possess a band gap; however,
constraining large-scale graphene in one dimension (GNRs)
or applying an electric field perpendicularly on the bilayer
graphene can induce the band gap (Figure 14).106 Recently,
both theoretical and experimental works have studied the
semiconductor properties of N-graphene.
Figure 14. Band structure around the k point of (i) large-area
graphene, (ii) graphene nanoribbons, (iii) unbiased bilayer graphene,
and (iv) bilayer graphene with an applied perpendicular field.106
4.2.1. Theoretical Part. Nitrogen doping can effectively
modulate the electrical properties of graphene. On the basis of
the investigation of C3N4 and C6N9H3 graphene,29 it has been
revealed that the band gap of N-graphene with a high N/C
ratio reached ∼5 eV. The band gap can be tuned by the
presence of external stress or adatoms. In another theoretical
work based on the study of delta-doping graphene,107 it has
been reported that the band gap could be opened only when
the nitrogen content was over ∼25%. However, delta-doping
may be unlikely to occur in practice. In the experimental study,
an obvious band gap has been observed on N-graphene with a
lower nitrogen content.70 Apart from the band gap, the
mobility and conductivity of N-graphene has also been
discussed theoretically by using the quantum-mechanical
Figure 15. (a) Schematic illustration of the N-graphene FET device. (b, c) Ids/Vds characteristics at various Vg's for the pristine graphene and NG
FET device. (d) Transfer characteristics of the pristine graphene and the NG.30
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Figure 16. Galvanostatic charge−discharge profile of N-graphene at a low current rate of 50 mA/g (a) and a higher current rate from 0.5 to 25 A/g
(c), (b) cycle performance and Coulombic efficiency of N-graphene at low current rate of 50 mA/g, (d) cycle performance and rate capabilities of Ngraphene at higher current rate from 0.5 to 25 A/g.115
graphene have reported a band gap in their works. Zhang et al.
showed the band gap in N-graphene with 2.9 at. % nitrogen
content was about 0.16 eV,50 which is still too low. Considering
the mobility and band gap of N-graphene obtained up to the
present, synthesization of N-graphene for practical applications
is still far off.
4.3. Lithium Ion Batteries. In recently years, graphene has
attracted great attention as a potential anode material in lithium
ion batteries (LIBs) because of its fascinating properties, such
as high electrical electronic properties, high surface area, and
excellent mechanical flexibility. Although graphene-based
materials can reach a high reversible capacity (1013−1054
mA h/g) at a low charge rate,114 it is still rate-limited at a high
charge/discharge rate (≥500 mA/g).115 Thus, a N-graphenebased device is proposed with the intent to achieve a high
reversible capacity at the high charge/discharge rate.
In earlier work, Reddy et al.43 obtained N-doped graphene
under the control of a CVD method. The reversible discharge
capacity of N-graphene was almost double compared with
pristine graphene because of the enhanced Li ion intercalation
with the introduction of nitrogen atoms. In another more
recent work,116 N-GNS with 2 at. % nitrogen content (57.4%
pyridinic, 35.0% pyrrolic, and 7.6% quaternary N) was
synthesized by heat treatment of GO in an NH3 atmosphere.
The N-graphene possessed a reversible capacity of around 900
mA h/g at a current density of 42 mA/g and a capacity of ∼250
mA h g−1 at a high current density of 2.1 A/g. In another work
in which N-graphene was synthesized by a similar heat
treatment method,115 N-graphene with 3.13 at. % nitrogen
content exhibited reversible capacities of 1043 mAh/g and 872
mAh/g in the first and 31st cycles at a low current rate of 50
doping level exhibits typical n-type semiconductor behavior
(Figure 15c, d).30 Compared with the mobility of pristine
graphene (300−1200 cm2 V−1 s−1), the mobility of N-graphene
reduces to 200−450 cm2 V−1 s−1. Using different precursors in
the CVD method, Jin et al.44 reported the mobility of Ngraphene with 2.4 at. % nitrogen content reduced by 2 orders of
magnitude compared with that of pristine graphene. In other
methods,50,59,63 such as N-graphene obtained through NH3
annealing after N+ ion irradiation,59 a much lower hole and
electron conductivity was observed compared with the pristine
graphene.
In the study of nitrogen-doped GNR (N-GNR), it has been
reported the N-GNR fabricated by high power electrical
annealing in NH3 showed typical n-type semiconductor
behavior, and the mobility was similar with the GNR annealed
in vacuum.31 The reason is that nitrogen atoms incorporate
mainly into the edge of GNR, and few charged impurities are
introduced, which will not degrade the mobility of GNR.
As discussed above, the electron mobility of graphene
decreases with the increment of band gap in most cases, which
is similar to the trend in studies of CNTs.106,112,113 Although
several theoretical studies27,111 and the recent work about NGNR31 have shown the mobility of N-graphene might be
maintained by controlling the nitrogen at a low doping level
and specific doping site, the scattering center induced by the
defects will drastically decrease the mobility of N-graphene in
practice. In addition, it is claimed that the grain boundaries in
N-graphene may also contribute to a decrement of mobility.36
Other than the mobility, a sizable band gap, preferably 0.4 eV
or higher, is also required in conventional FET (the band gap of
silicon is 1.1 eV).106 Until now, only a few studies of N791
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and pure CdS, which can be attributed to the hampering of the
radiative recombination of the electron−hole pairs induced by
enhanced electron transportation from CdS to N-graphene.
Moreover, CdS anchored on N-graphene with 2 wt % nitrogen
content showed the best catalytic activity. It reveals that a
proper junction structure is required for the highest photocatalytic activity.
mA/g, respectively (Figure 16 a, b). At a higher current rate of
25 A/g, the reversible capacities of N-graphene still reached 199
mAh/g (Figure 16 c, d).
The excellent performance of N-graphene can be ascribed to
many factors, such as the introduction of nitrogen atoms, the
defects and disordered surface morphology induced by doping,
increased electrode/electrolyte wettability, and improved
electrochemical performance. Notably, in the above studies,
the types of pyridinic and pyrrolic N are predominant in the Ngraphene. Through the study of nitrogen-doped graphite, it has
been revealed that both the pyridinic and quaternary N played
an effective role in lithium intercalation and extraction.117 Thus,
graphene with a large quaternary N content might also be used
in LIBs.
4.4. Devices in Other Fields. N-Graphene has been
applied in the field of ultracapacitors.69 The ultracapacitor
based on N-graphene has shown a long cycle life (Figure 17a).
5. CONCLUSION
In summary, many research works on N-graphene have
emerged in recent years. Various synthesis approaches and
characterization techniques have been explored to obtain and
characterize N-graphene. The N doping offers an effective way
to tailor the properties of graphene, thus making N-graphene a
promising material for use in many fields. However, the method
for the production of large-scale N-graphene is still lacking;
thus, new methods are required. Moreover, synthesizing Ngraphene meets problems similar to those encountered during
fabricating N-CNT. First, controlling the nitrogen type and
distribution is unresolved. Second, to achieve nitrogen doping
at specific positions and with precise control of doping content
is still a challenge. For FET application, the doping location and
doping content is critical not to decrease the electron mobility
drastically while opening a suitable band gap. For electrocatalysis, the correlation between the activity and nitrogen type
needs to be identified, and controlling the specific nitrogen type
in N-graphene is required for high performance catalysts. For
other applications, such as LIBs and ultracapacitors, a specific
nitrogen type may also be required. Another issue to be
considered is defects and distortion. Defects are inevitable
during the synthesis process of N-graphene. They will decrease
the mobility of N-graphene; however, their presence will
benefit the catalytic reaction for ORR and LIBs. Depending on
the application, choosing or finding an appropriate approach is
required.
Figure 17. (a) The cycling tests for the ultracapacitors based on Ni
and paper substrates up to 10 000 cycles. (b) The specific capacitances
measured in 6 M KOH and organic electrolytes.69
Moreover, a N-graphene-based device showed a much higher
capacitance than a device based on pristine graphene in both
KOH and organic electrolyte (Figure 17b). By calculating the
binding energy between the potassium ion and nitrogen
configurations at different positions of N-graphene, it has been
revealed that the basal-plane pyridinic N exhibited the largest
binding energy. Thus, basal-plane pyridinic N was claimed to
have a dominant role in the capacitance enhancement. Pyrrolic
N also showed a large binding energy with ion, but the negative
charge of pyrrolic N would cause too strong binding for the
reversible charging/discharging process, which was reflected by
the lower Coulombic efficiencies of N-graphene with a large
proportion of pyrrolic N. Therefore, controlling the appropriate
nitrogen configuration can greatly promote the capacitance of
N-graphene.
Study has shown that N-graphene has a better electron
transfer efficiency than pristine graphene,68,72 rendering its
potential use for electrochemical sensing. Because glucose
oxidase (GOx) could oxidize glucose with oxygen and produce
gluconic acid and H2O2, Wang et al.68 fabricated the glucose
sensor by immobilizing GOx on the biocompatible N-graphene
surface. It was observed that the GOx redox peak current on Ndoped graphene was greatly improved over that on graphene,
which demonstrated the enhanced electron transfer efficiency
of N-graphene. This kind of biosensor shows a good response
for glucose concentrations ranging from 0.01 to 0.5 mM in the
presence of other molecules.
Apart from the above applications, N-graphene also has been
used as a support to anchor quantum dots toward highperformance photocatalysts.118 N-Graphene/CdS nanocomposites have a higher photocatalytic activity than graphene/CdS
■
AUTHOR INFORMATION
Corresponding Author
*Phone: (65) 6316 8866. Fax: (65) 6794 7553. E-mail:
WangXin@ntu.edu.sg.
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS
This work is supported by the academic research fund AcRF
tier 2 (MOE2009-T2-2-024), Ministry of Education, Singapore,
and competitive research program (2009 NRF-CRP 001-032),
National Research Foundation, Singapore.
■
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