This document summarizes research on using nitrogen-containing carbon nanotubes as supports for platinum nanoparticles as an alternative anode catalyst for direct methanol fuel cells. Key points:
1. Nitrogen-containing carbon nanotubes were synthesized using an alumina membrane template and pyrolysis of polyvinylpyrrolidone polymer.
2. Highly dispersed platinum nanoparticles around 3nm in size were uniformly deposited on the nitrogen-containing carbon nanotubes.
3. Electrochemical testing found the platinum catalyst supported on nitrogen-containing carbon nanotubes had over 10 times higher catalytic activity for methanol oxidation compared to a commercial platinum on carbon catalyst.
Maiyalagan, Synthesis and electro catalytic activity of methanol oxidation on...kutty79
Template synthesis of various nitrogen containing carbon nanotubes using different nitrogen containing polymers and the variation of nitrogen
content in carbon nanotube (CNT) on the behaviour of supported Pt electrodes in the anodic oxidation of methanol in direct methanol fuel cells was
investigated. Characterizations of the as-prepared catalysts are investigated by electron microscopy and electrochemical analysis. The catalyst with
N-containing CNT as a support exhibits a higher catalytic activity than that carbon supported platinum electrode and CNT supported electrodes.
The N-containing CNT supported electrodes with 10.5% nitrogen content show a higher catalytic activity compared to other N-CNT supported
electrodes. This could be due to the existence of additional active sites on the surface of the N-containing CNT supported electrodes, which favours
better dispersion of Pt particles. Also, the strong metal-support interaction plays a major role in enhancing the catalytic activity for methanol
oxidation.
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
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
Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 ...Pawan Kumar
We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2.
Asymmetric Multipole Plasmon-Mediated Catalysis Shifts the Product Selectivit...Pawan Kumar
Cu/TiO2 is a well-known photocatalyst for the photocatalytic transformation of CO2 into methane. The formation of C2+ products such as ethane and ethanol rather than methane is more interesting due to their higher energy density and economic value, but the formation of C–C bonds is currently a major challenge in CO2 photoreduction. In this context, we report the dominant formation of a C2 product, namely, ethane, from the gas-phase photoreduction of CO2 using TiO2 nanotube arrays (TNTAs) decorated with large-sized (80–200 nm) Ag and Cu nanoparticles without the use of a sacrificial agent or hole scavenger. Isotope-labeled mass spectrometry was used to verify the origin and identity of the reaction products. Under 2 h AM1.5G 1-sun illumination, the total rate of hydrocarbon production (methane + ethane) was highest for AgCu-TNTA with a total CxH2x+2 rate of 23.88 μmol g–1 h–1. Under identical conditions, the CxH2x+2 production rates for Ag-TNTA and Cu-TNTA were 6.54 and 1.39 μmol g–1 h–1, respectively. The ethane selectivity was the highest for AgCu-TNTA with 60.7%, while the ethane selectivity was found to be 15.9 and 10% for the Ag-TNTA and Cu-TNTA, respectively. Adjacent adsorption sites in our photocatalyst develop an asymmetric charge distribution due to quadrupole resonances in large metal nanoparticles and multipole resonances in Ag–Cu heterodimers. Such an asymmetric charge distribution decreases adsorbate–adsorbate repulsion and facilitates C–C coupling of reaction intermediates, which otherwise occurs poorly in TNTAs decorated with small metal nanoparticles.
Maiyalagan,Electro oxidation of methanol on ti o2 nanotube supported platinum...kutty79
TiO2 nanotubes have been synthesized using anodic alumina membrane as template. Highly dispersed
platinum nanoparticles have been supported on the TiO2 nanotube. The supported system
has been characterized by electron microscopy and electrochemical analysis. SEM image shows
that the nanotubes are well aligned and the TEM image shows that the Pt particles are uniformly
distributed over the TiO2 nanotube support. A homogeneous structure in the composite nanomaterials
is indicated by XRD analysis. The electrocatalytic activity ofthe platinum catalyst supported on
TiO2 nanotubes for methanol oxidation is found to be better than that of the standard commercial
E-TEK catalyst.
Maiyalagan,Template synthesis and characterization of well aligned nitrogen c...kutty79
The synthesis of well-aligned nitrogen containing carbon nanotubes by pyrolysis of polyvinyl pyrrolidone (PVP) on alumina membrane
template is described. The nanotubes were characterized by elemental analysis, electron microscopic analyses, Raman, IR and X-ray photoelectron
(XPS) spectroscopic techniques. SEM, transmission electron microscopy (TEM) and AFM images reveal the hollow structures and
vertically aligned features of the nanotubes. Raman spectrum shows the characteristic bands at 1290 cm−1 (D-band) and 1590 cm−1 (G-band).
IR spectral bands indicated the characteristic C–N bonds in carbon nanotubes. This confirms the presence of nitrogen atoms in the carbon
framework. The XPS and elemental analyses further indicate significant amount of nitrogen in the nanotubes. IR, elemental and XPS analyses
clearly provide evidence for the presence of nitrogen in carbon nanotubes.
Maiyalagan, Synthesis and electro catalytic activity of methanol oxidation on...kutty79
Template synthesis of various nitrogen containing carbon nanotubes using different nitrogen containing polymers and the variation of nitrogen
content in carbon nanotube (CNT) on the behaviour of supported Pt electrodes in the anodic oxidation of methanol in direct methanol fuel cells was
investigated. Characterizations of the as-prepared catalysts are investigated by electron microscopy and electrochemical analysis. The catalyst with
N-containing CNT as a support exhibits a higher catalytic activity than that carbon supported platinum electrode and CNT supported electrodes.
The N-containing CNT supported electrodes with 10.5% nitrogen content show a higher catalytic activity compared to other N-CNT supported
electrodes. This could be due to the existence of additional active sites on the surface of the N-containing CNT supported electrodes, which favours
better dispersion of Pt particles. Also, the strong metal-support interaction plays a major role in enhancing the catalytic activity for methanol
oxidation.
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
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
Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 ...Pawan Kumar
We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2.
Asymmetric Multipole Plasmon-Mediated Catalysis Shifts the Product Selectivit...Pawan Kumar
Cu/TiO2 is a well-known photocatalyst for the photocatalytic transformation of CO2 into methane. The formation of C2+ products such as ethane and ethanol rather than methane is more interesting due to their higher energy density and economic value, but the formation of C–C bonds is currently a major challenge in CO2 photoreduction. In this context, we report the dominant formation of a C2 product, namely, ethane, from the gas-phase photoreduction of CO2 using TiO2 nanotube arrays (TNTAs) decorated with large-sized (80–200 nm) Ag and Cu nanoparticles without the use of a sacrificial agent or hole scavenger. Isotope-labeled mass spectrometry was used to verify the origin and identity of the reaction products. Under 2 h AM1.5G 1-sun illumination, the total rate of hydrocarbon production (methane + ethane) was highest for AgCu-TNTA with a total CxH2x+2 rate of 23.88 μmol g–1 h–1. Under identical conditions, the CxH2x+2 production rates for Ag-TNTA and Cu-TNTA were 6.54 and 1.39 μmol g–1 h–1, respectively. The ethane selectivity was the highest for AgCu-TNTA with 60.7%, while the ethane selectivity was found to be 15.9 and 10% for the Ag-TNTA and Cu-TNTA, respectively. Adjacent adsorption sites in our photocatalyst develop an asymmetric charge distribution due to quadrupole resonances in large metal nanoparticles and multipole resonances in Ag–Cu heterodimers. Such an asymmetric charge distribution decreases adsorbate–adsorbate repulsion and facilitates C–C coupling of reaction intermediates, which otherwise occurs poorly in TNTAs decorated with small metal nanoparticles.
Maiyalagan,Electro oxidation of methanol on ti o2 nanotube supported platinum...kutty79
TiO2 nanotubes have been synthesized using anodic alumina membrane as template. Highly dispersed
platinum nanoparticles have been supported on the TiO2 nanotube. The supported system
has been characterized by electron microscopy and electrochemical analysis. SEM image shows
that the nanotubes are well aligned and the TEM image shows that the Pt particles are uniformly
distributed over the TiO2 nanotube support. A homogeneous structure in the composite nanomaterials
is indicated by XRD analysis. The electrocatalytic activity ofthe platinum catalyst supported on
TiO2 nanotubes for methanol oxidation is found to be better than that of the standard commercial
E-TEK catalyst.
Maiyalagan,Template synthesis and characterization of well aligned nitrogen c...kutty79
The synthesis of well-aligned nitrogen containing carbon nanotubes by pyrolysis of polyvinyl pyrrolidone (PVP) on alumina membrane
template is described. The nanotubes were characterized by elemental analysis, electron microscopic analyses, Raman, IR and X-ray photoelectron
(XPS) spectroscopic techniques. SEM, transmission electron microscopy (TEM) and AFM images reveal the hollow structures and
vertically aligned features of the nanotubes. Raman spectrum shows the characteristic bands at 1290 cm−1 (D-band) and 1590 cm−1 (G-band).
IR spectral bands indicated the characteristic C–N bonds in carbon nanotubes. This confirms the presence of nitrogen atoms in the carbon
framework. The XPS and elemental analyses further indicate significant amount of nitrogen in the nanotubes. IR, elemental and XPS analyses
clearly provide evidence for the presence of nitrogen in carbon nanotubes.
Mixed-Valence Single-Atom Catalyst Derived from Functionalized GraphenePawan Kumar
Single-atom catalysts (SACs) aim at bridging the gap between homogeneous and heterogeneous catalysis. The challenge is the development of materials with ligands enabling coordination of metal atoms in different valence states, and preventing leaching or nanoparticle formation. Graphene functionalized with nitrile groups (cyanographene) is herein employed for the robust coordination of Cu(II) ions, which are partially reduced to Cu(I) due to graphene-induced charge transfer. Inspired by nature's selection of Cu(I) in enzymes for oxygen activation, this 2D mixed-valence SAC performs flawlessly in two O2-mediated reactions: the oxidative coupling of amines and the oxidation of benzylic CH bonds toward high-value pharmaceutical synthons. High conversions (up to 98%), selectivities (up to 99%), and recyclability are attained with very low metal loadings in the reaction. The synergistic effect of Cu(II) and Cu(I) is the essential part in the reaction mechanism. The developed strategy opens the door to a broad portfolio of other SACs via their coordination to various functional groups of graphene, as demonstrated by successful entrapment of FeIII/FeII single atoms to carboxy-graphene.
Maiyalagan,Electrochemical oxidation of methanol on pt v2 o5–c composite cata...kutty79
Platinum nanoparticles have been supported on V2O5–C composite through the reduction of chloroplatinic
acid with formaldehyde. The catalyst was characterized by X-ray diffraction and transmission electron
microscopy. Catalytic activity and stability for the oxidation of methanol were studied by using
cyclic voltammetry and chronoamperometry. Pt/V2O5–C composite anode catalyst on glassy carbon electrode
show higher electro-catalytic activity for the oxidation of methanol. High electro-catalytic activities
and good stabilities could be attributed to the synergistic effect between Pt and V2O5, avoiding the electrodes
being poisoned.
Consistently High Voc Values in p-i-n Type Perovskite Solar Cells Using Ni3+-...Pawan Kumar
Leading edge p-i-n type halide perovskite solar cells (PSCs) severely underperform n-i-p PSCs. p-i-n type PSCs that use PEDOT:PSS hole transport layers (HTLs) struggle to generate open-circuit photovoltage values higher than 1 V. NiO HTLs have shown greater promise in achieving high Voc values albeit inconsistently. In this report, a NiO nanomesh with Ni3+ defect grown by the hydrothermal method was used to obtain PSCs with Voc values that consistently exceeded 1.10 V (champion Voc = 1.14 V). A champion device photoconversion efficiency of 17.75% was observed. Density functional theory modeling was used to understand the interfacial properties of the NiO/perovskite interface. The PCE of PSCs constructed using the Ni3+-doped NiO nanomesh HTL was ∼34% higher than that of conventional compact NiO-based perovskite solar cells. A suite of characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy, intensity-modulated photocurrent spectroscopy, intensity-modulated photovoltage spectroscopy, time-resolved photoluminescence, steady-state photoluminescence, and Kelvin probe force microscopy provided evidence of better film quality, enhanced charge transfer, and suppressed charge recombination in PSCs based on hydrothermally grown NiO nanostructures.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after 24 h irradiation was 9934 μmol g−1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride 145 μmol g−1cat under identical conditions. The presence of triethylamine was found to be vital for the higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for subsequent six runs without significant loss in photo activity.
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 down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C3N5 blended with MAxFA1–xPb(I0.85Br0.15)3 perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intra sheet cavity make it an attractive supramolecular adsorbent for environmental applications.
Synthesis, characterization and electrocatalytic activity of silver nanorods ...kutty79
This paper describes a simple method of synthesizing silver nanorods using the polyol process, where propylene glycol serves both as a reducing
agent and as a solvent in the presence of a capping reagent such as polyvinylpyrrolidone (PVP). The diameter and length of silver nanorods could be
controlled by changing the AgNO3/PVP ratio. The end-to-end assembly of the silver nanorods was found. The silver nanorods were characterized by
using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and absorption spectroscopy. The catalytic activity of a
glassy carbon electrode with Ag nanorods exhibits extraordinary electrocatalytic activities towards the electro-reduction of benzyl chloride.
Maiyalagan, Fabrication and characterization of uniform ti o2 nanotube arrays...kutty79
TiO2 nanotubes have been synthesized by sol–gel template method using alumina membrane.
Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, UV absorption
spectrum and X-ray diffraction techniques have been used to investigate the structure, morphology
and optical properties of TiO2 nanotubes. SEM image showed that TiO2 nanotubes obtained were ordered and
uniform. The diameter and length of the nanotubes were decided by the pore size and thickness of alumina
template. Raman and XRD measurements confirmed the crystallinity and anatase phase of the TiO2 nanotubes.
The optical absorption measurement of TiO2 nanotubes exhibits a blue shift with respect to that of the
bulk TiO2 owing to the quantum size effect.
In promotional activities, the firm gets its chance to communicate with potential customers, “To beat the drum” about its product.
We will discuss every aspect of this “P” of Marketing Mix in detail one by one:
Meaning and Importance
The Communication Process
Determination of Promotional Mix
Determination of total promotional Appropriation
The Campaign Concept
Over the years, many different methods have been used by individual companies to establish base prices for their products.
Most of these approaches are variations of following methods:
Prices are based on total cost plus a desired profit
Prices based on market demand and supply
Prices based on competitive market conditions
Mixed-Valence Single-Atom Catalyst Derived from Functionalized GraphenePawan Kumar
Single-atom catalysts (SACs) aim at bridging the gap between homogeneous and heterogeneous catalysis. The challenge is the development of materials with ligands enabling coordination of metal atoms in different valence states, and preventing leaching or nanoparticle formation. Graphene functionalized with nitrile groups (cyanographene) is herein employed for the robust coordination of Cu(II) ions, which are partially reduced to Cu(I) due to graphene-induced charge transfer. Inspired by nature's selection of Cu(I) in enzymes for oxygen activation, this 2D mixed-valence SAC performs flawlessly in two O2-mediated reactions: the oxidative coupling of amines and the oxidation of benzylic CH bonds toward high-value pharmaceutical synthons. High conversions (up to 98%), selectivities (up to 99%), and recyclability are attained with very low metal loadings in the reaction. The synergistic effect of Cu(II) and Cu(I) is the essential part in the reaction mechanism. The developed strategy opens the door to a broad portfolio of other SACs via their coordination to various functional groups of graphene, as demonstrated by successful entrapment of FeIII/FeII single atoms to carboxy-graphene.
Maiyalagan,Electrochemical oxidation of methanol on pt v2 o5–c composite cata...kutty79
Platinum nanoparticles have been supported on V2O5–C composite through the reduction of chloroplatinic
acid with formaldehyde. The catalyst was characterized by X-ray diffraction and transmission electron
microscopy. Catalytic activity and stability for the oxidation of methanol were studied by using
cyclic voltammetry and chronoamperometry. Pt/V2O5–C composite anode catalyst on glassy carbon electrode
show higher electro-catalytic activity for the oxidation of methanol. High electro-catalytic activities
and good stabilities could be attributed to the synergistic effect between Pt and V2O5, avoiding the electrodes
being poisoned.
Consistently High Voc Values in p-i-n Type Perovskite Solar Cells Using Ni3+-...Pawan Kumar
Leading edge p-i-n type halide perovskite solar cells (PSCs) severely underperform n-i-p PSCs. p-i-n type PSCs that use PEDOT:PSS hole transport layers (HTLs) struggle to generate open-circuit photovoltage values higher than 1 V. NiO HTLs have shown greater promise in achieving high Voc values albeit inconsistently. In this report, a NiO nanomesh with Ni3+ defect grown by the hydrothermal method was used to obtain PSCs with Voc values that consistently exceeded 1.10 V (champion Voc = 1.14 V). A champion device photoconversion efficiency of 17.75% was observed. Density functional theory modeling was used to understand the interfacial properties of the NiO/perovskite interface. The PCE of PSCs constructed using the Ni3+-doped NiO nanomesh HTL was ∼34% higher than that of conventional compact NiO-based perovskite solar cells. A suite of characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy, intensity-modulated photocurrent spectroscopy, intensity-modulated photovoltage spectroscopy, time-resolved photoluminescence, steady-state photoluminescence, and Kelvin probe force microscopy provided evidence of better film quality, enhanced charge transfer, and suppressed charge recombination in PSCs based on hydrothermally grown NiO nanostructures.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after 24 h irradiation was 9934 μmol g−1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride 145 μmol g−1cat under identical conditions. The presence of triethylamine was found to be vital for the higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for subsequent six runs without significant loss in photo activity.
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 down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C3N5 blended with MAxFA1–xPb(I0.85Br0.15)3 perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intra sheet cavity make it an attractive supramolecular adsorbent for environmental applications.
Synthesis, characterization and electrocatalytic activity of silver nanorods ...kutty79
This paper describes a simple method of synthesizing silver nanorods using the polyol process, where propylene glycol serves both as a reducing
agent and as a solvent in the presence of a capping reagent such as polyvinylpyrrolidone (PVP). The diameter and length of silver nanorods could be
controlled by changing the AgNO3/PVP ratio. The end-to-end assembly of the silver nanorods was found. The silver nanorods were characterized by
using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and absorption spectroscopy. The catalytic activity of a
glassy carbon electrode with Ag nanorods exhibits extraordinary electrocatalytic activities towards the electro-reduction of benzyl chloride.
Maiyalagan, Fabrication and characterization of uniform ti o2 nanotube arrays...kutty79
TiO2 nanotubes have been synthesized by sol–gel template method using alumina membrane.
Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, UV absorption
spectrum and X-ray diffraction techniques have been used to investigate the structure, morphology
and optical properties of TiO2 nanotubes. SEM image showed that TiO2 nanotubes obtained were ordered and
uniform. The diameter and length of the nanotubes were decided by the pore size and thickness of alumina
template. Raman and XRD measurements confirmed the crystallinity and anatase phase of the TiO2 nanotubes.
The optical absorption measurement of TiO2 nanotubes exhibits a blue shift with respect to that of the
bulk TiO2 owing to the quantum size effect.
In promotional activities, the firm gets its chance to communicate with potential customers, “To beat the drum” about its product.
We will discuss every aspect of this “P” of Marketing Mix in detail one by one:
Meaning and Importance
The Communication Process
Determination of Promotional Mix
Determination of total promotional Appropriation
The Campaign Concept
Over the years, many different methods have been used by individual companies to establish base prices for their products.
Most of these approaches are variations of following methods:
Prices are based on total cost plus a desired profit
Prices based on market demand and supply
Prices based on competitive market conditions
Performance of carbon nanofiber supported pd–ni catalysts for electro oxidati...suresh899
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.
Performance of carbon nanofiber supported pd–ni catalysts for electro oxidati...sunilove
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.
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Nitrogen containing carbon nanotubes as supports for pt – alternate anodes for fuel cell applications
1. Electrochemistry Communications 7 (2005) 905–912
www.elsevier.com/locate/elecom
Nitrogen containing carbon nanotubes as supports for
Pt – Alternate anodes for fuel cell applications
T. Maiyalagan, B. Viswanathan *, U.V. Varadaraju
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India
Received 7 June 2005; accepted 7 July 2005
Available online 8 August 2005
Abstract
Aligned nitrogen containing carbon nanotubes have been synthesized using Anodisc alumina membrane as template. Highly dis-
persed platinum nanoparticles have been supported on the nitrogen containing carbon nanotubes. Nitrogen containing carbon
nanotubes as platinum catalyst supports were characterized by electron microscopic technique and electrochemical analysis. The
EDX patterns show the presence of Pt and the micrograph of TEM shows that the Pt particles are uniformly distributed on the
surface of the nitrogen containing carbon nanotube with an average particle size of 3 nm. Cyclic voltammetry studies revealed a
higher catalytic activity of the nitrogen containing carbon nanotube supported Pt catalysts.
Ó 2005 Elsevier B.V. All rights reserved.
Keywords: Nitrogen containing carbon nanotubes; Template synthesis; Alumina template; Catalyst support; Methanol oxidation
1. Introduction Pt based catalysts. High noble metal loadings on the
electrode [4,5] and the use of perfluorosulfonic acid
Since the last decade, fuel cells have been receiving an membranes significantly contribute to the cost of the de-
increased attention due to the depletion of fossil fuels vices. An efficient way to decrease the loadings of pre-
and rising environmental pollution. Fuel cells have been cious platinum metal catalysts and higher utilization of
demonstrated as interesting and very promising alterna- Pt particles is by better dispersion of the desired metal
tives to solve the problem of clean electric power gener- on the suitable support [6]. In general, small particle size
ation with high efficiency. Among the different types of and high dispersion of platinum on the support will re-
fuel cells, direct methanol fuel cells (DMFCs) are excel- sult in high electrocatalytic activity. Carbon materials
lent power sources for portable applications owing to its possess suitable properties for the design of electrodes
high energy density, ease of handling liquid fuel, low in electrochemical devices. Carbon is an ideal material
operating temperatures (60–100 °C) and quick start up for supporting nano-sized metallic particles in the elec-
[1,2]. Furthermore, methanol fuel cell seems to be highly trode for fuel cell applications. No other material except
promising for large-scale commercialization in contrast carbon material has the essential properties of electronic
to hydrogen-fed cells, especially in transportation [3]. conductivity, corrosion resistance, surface properties,
The limitation of methanol fuel cell system is due to and the low cost required for the commercialization of
low catalytic activity of the electrodes, especially the an- fuel cells. In general, the conventional supports namely
odes and at present, there is no practical alternative to carbon black is used for the dispersion of Pt particles [7].
The appearance of novel carbon support materials,
*
Corresponding author. Tel.: +91 044 22574200; fax: +91 44
such as graphite nanofibers (GNFs) [8,9], carbon nano-
22574202. tubes (CNTs) [10–17], carbon nanohorns [18], and car-
E-mail address: bvnathan@iitm.ac.in (B. Viswanathan). bon nanocoils [19–22], provides new opportunities of
1388-2481/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.elecom.2005.07.007
2. 906 T. Maiyalagan et al. / Electrochemistry Communications 7 (2005) 905–912
carbon supports for fuel cell applications. Bessel et al. [8] alumina template by wetting method [28]. After
and Steigerwalt et al. [9] used GNFs as supports for Pt complete solvent evaporation, the membrane was placed
and Pt–Ru alloy electrocatalysts and observed better in a quartz tube (30 cm length, 3.0 cm diameter), kept in
activity for methanol oxidation. The high electronic a tubular furnace and carbonized at 1173 K under Ar
conductivity of GNFs and the specific crystallographic gas flow. After 3 h of carbonization, the quartz tube
orientation of the metal particles resulting from well- was cooled to room temperature. The resulting template
ordered GNF support were believed to be the important with carbon–nitrogen composite was immersed in 48%
factors for the observed enhanced electrocatalytic activ- HF at room temperature for 24 h to remove the alumina
ity. The morphology and the nature of the functional template and the nitrogen containing CNTs were
groups of the support influence the activity of fuel cell obtained as an insoluble fraction. The nanotubes were
electrocatalyts [23–26]. Carbon with sulphur or nitrogen then washed with distilled water to remove the residual
based functionality [25], can influence the activity of the HF and dried at 393 K.
catalyst.
The present report focuses on the efforts undertaken 2.3. Loading of Pt catalyst inside nanotube
to develop unconventional supports based platinum
catalysts for methanol oxidation. Nitrogen containing Platinum nanoclusters were loaded inside the N-CNT
carbon nanotubes were used to disperse the platinum as follows; the C/alumina composite obtained (before
particles effectively without sintering and to increase the dissolution of template membrane) was immersed
the catalytic activity for methanol oxidation. The tubu- in 73 mM H2PtCl6 (aq) for 12 h. After immersion, the
lar morphology and the nitrogen functionality of the membrane was dried in air and the ions were reduced
support have influence on the dispersion as well as to the corresponding metal(s) by a 3 h exposure to flow-
the stability of the electrode. In this communication ing H2 gas at 823 K. The underlying alumina was then
the preparation of highly dispersed platinum supported dissolved by immersing the composite in 48% HF for
on nitrogen containing carbon nanotubes, the evalua- 24 h. This procedure resulted in the formation of Pt
tion of the activity for the methanol oxidation of these nanocluster loaded N-CNT and the complete removal
electrodes and comparison with the activity of conven- of fluorine and aluminum was confirmed by EDX
tional electrodes are reported. analysis.
2.4. Preparation of working electrode
2. Experimental
Glassy carbon (GC) (Bas electrode, 0.07 cm2) was
2.1. Materials polished to a mirror finish with 0.05 m alumina suspen-
sions before each experiment and served as an underly-
All the chemicals used were of analytical grade. Poly- ing substrate of the working electrode. In order to
vinyl pyrrolidone (Sisco Research Laboratories, India), prepare the composite electrode, the nanotubes were
dichloromethane and concentrated HF (both from dispersed ultrasonically in water at a concentration of
Merck) were used. Hexachloroplatinic acid was ob- 1 mg mlÀ1 and 20 ll aliquot was transferred on to a
tained from Aldrich. 20 wt% Pt/Vulcan carbons were polished glassy carbon substrate. After the evaporation
procured from E-TEK. Methanol and sulphuric acid of water, the resulting thin catalyst film was covered
were obtained from Fischer chemicals. The alumina with 5 wt% Nafion solution. Then the electrode was
template membranes (Anodisc 47) with 200 nm diameter dried at 353 K and used as the working electrode.
pores were obtained from Whatman Corp. Nafion
5 wt% solution was obtained from Dupont and was used 2.5. Characterization methods
as received.
The chemical composition of the nanotubes was
2.2. Synthesis of nitrogen containing carbon nanotubes determined by elemental analysis using Hereaus CHN
analyzer after the removal of alumina template. The
Pyrolysis of nitrogen containing polymers is a facile scanning electron micrographs were obtained using
method for the preparation of carbon nanotube materi- JEOL JSM-840 model, working at 15 keV. The nano-
als containing nitrogen substitution in the carbon frame- tubes were sonicated in acetone for 20 min and then
work. Nitrogen containing carbon nanotubes were were dropped on the cleaned Si substrates. The AFM
synthesized by impregnating polyvinylpyrrolidone imaging was performed in air using the Nanoscope IIIA
(PVP) inside the alumina membrane template and subse- atomic force microscope (Digital Instruments, St. Bar-
quent carbonization of the polymer [27]. Polyvinylpyr- bara, CA) operated in contact mode. For transmission
rolidone (PVP – 5 g) was dissolved in dichloromethane electron microscopic studies, the nanotubes dispersed
(20 ml) and impregnated directly in the pores of the in ethanol were placed on the copper grid and the
3. T. Maiyalagan et al. / Electrochemistry Communications 7 (2005) 905–912 907
images were obtained using Phillips 420 model, operat- nanotubes is shown in Fig. 1(a). Fig. 1(b) shows lateral
ing at 120 keV. view of the nitrogen containing carbon nanotubes with
low magnification and Fig. 1(c) shows lateral view of
2.6. Electrochemical measurements the nitrogen containing carbon nanotubes with high
magnification. The hollow structure and well alignment
All electrochemical studies were carried out using a of the nitrogen containing carbon nanotubes have been
BAS 100 electrochemical analyzer. A conventional identified by SEM.
three-electrode cell consisting of the GC (0.07 cm2) AFM images of the nitrogen containing carbon nano-
working electrode, Pt plate (5 cm2) as counter electrode tubes deposited on a silicon substrate are shown in
and Ag/AgCl reference electrode were used for the cyclic Fig. 2. The AFM tip was carefully scanned across the
voltammetry (CV) studies. The CV experiments were tube surface in a direction perpendicular to the tube
performed using 1 M H2SO4 solution in the absence axis. From the AFM images, it is inferred that a part
and presence of 1 M CH3OH at a scan rate of of the long nanotube is appearing to be cylindrical in
50 mV sÀ1. All the solutions were prepared by using ul- shape and is found to be terminated by a symmetric
tra pure water (Millipore, 18 MX). The electrolytes were hemispherical cap. Because of the finite size of the
degassed with nitrogen gas before the electrochemical AFM tip, convolution between the blunt AFM tip and
measurements. the tube body will be giving rise to an apparently greater
lateral dimension than the actual diameter of the tube
[29].
3. Results and discussion The TEM images are shown in Fig. 3(a)–(c). The
open end of the tubes observed by TEM shows that
Elemental analysis was conducted to examine the nanotubes are hollow and the outer diameter of
whether nitrogen has really entered the carbon nanotube the nanotube closely match with the pore diameter of
framework. It has been found that the samples prepared template used, with a diameter of 200 nm and a length
contained about 87.2% carbon and 6.6% nitrogen (w/w). of approx. 40–50 lm. It is evident from the micrographs
The SEM images of the nitrogen containing carbon that there is no amorphous material present in the nano-
nanotubes support are shown in Fig. 1(a)–(c). Top view tube. Fig. 3(c) shows the TEM image of Pt nanoparticles
of the vertically aligned nitrogen containing carbon filled carbon nanotubes. TEM pictures reveal that the Pt
Fig. 1. SEM images of the nitrogen containing carbon nanotubes: (a) the top view of the nanotubes; (b) side view of the vertically aligned nanotubes
and (c) high magnification lateral view of the nanotubes.
4. 908 T. Maiyalagan et al. / Electrochemistry Communications 7 (2005) 905–912
Fig. 2. AFM image of the nitrogen containing carbon nanotubes.
Fig. 3. TEM images of the nitrogen containing carbon nanotubes: (a) at lower magnification; (b) at higher magnification image of the individual
nanotube (an arrow indicating the open end of the tube) and (c) Pt filled nitrogen containing carbon nanotubes.
5. T. Maiyalagan et al. / Electrochemistry Communications 7 (2005) 905–912 909
particles have been homogeneously dispersed on the the current increases quickly due to dehydrogenation
nanotubes and particle sizes were found to be around of methanol followed by the oxidation of absorbed
3 nm. The optimal Pt particle size for reactions in the methanol residues and reaches a maximum in the poten-
H2/O2 fuel cell is 3 nm [30]. The importance of the Pt tial range between 0.8 and 1.0 V vs. Ag/AgCl. In the
particle size on the activity for methanol oxidation is cathodic scan, the re-oxidation of methanol is clearly
due to the structure sensitive nature of the reaction observed due to the reduction of oxide of platinum.
and the fact that particles with different sizes will Electrocatalytic activity of methanol oxidation has been
have different dominant crystal planes and hence the dif- found to be strongly influenced by the metal dispersion.
ferent intercrystallite distances, which might influence Pure Pt electrode shows an activity of 0.167 mA cmÀ2.
methanol adsorption. The commercial Pt/C has a very The Pt/N-CNT shows a higher activity of 13.3 mA cmÀ2
high specific surface area but contributed mostly by where as conventional 20% Pt/Vulcan (E-TEK)
micropores less than 1 nm and are therefore more diffi- electrode shows less activity of 1.3 mA cmÀ2 compared
cult to be fully accessible. It has been reported that the to nitrogen containing carbon nanotube supported
mean value of particle size for 20% Pt/Vulcan electrode. The nitrogen containing carbon nanotube
(E-TEK) catalyst was 2.6 nm [31]. The EDX pattern of supported electrodes shows a ten fold increase in the
the as synthesized catalyst shows the presence of Pt catalytic activity compared to the E-TEK electrode.
particles in the carbon nanotubes and also the complete The Pt/N-CNT electrode showed higher electrocatalytic
removal of fluorine and aluminum has also been activity for methanol oxidation than commercial
confirmed in Fig. 4. It has been reported that the Pt/Vulcan (E-TEK) electrode. The anodic current
electronic and physical structures of a Pt particle density of Pt/N-CNT electrode is found to be higher
deposited on carbon differ from those of the bulk Pt. than that of Pt/Vulcan (E-TEK) electrode, which indi-
The electronic change in Pt/C is considered as a result cates that the catalyst prepared with nitrogen containing
of functional groups of the carbon support that might carbon nanotubes as the support has excellent catalytic
influence the electronic structure of Pt particulate activity on methanol electrooxidation.
[32–36]. The nitrogen functional group on the carbon The onset potential and the forward-scan peak current
nanotubes surface intensifies the electron withdrawing density for the different electrodes are given in Table 1.
effect against Pt and the decreased electron density of The onset potential of methanol oxidation at nitrogen
platinum facilitate oxidation of methanol. containing carbon nanotube supported catalysts occurs
Fig. 5(a)–(c) shows the cyclic voltammogram of at 0.22 V, which is relatively more negative to that of
methanol oxidation. Fig. 5(c) shows the cyclic voltam- the other catalysts. This may be attributed to the high dis-
mogram of Pt/N-CNT electrode in 1 M H2SO4/1 M persion of platinum catalysts and the nitrogen functional
CH3OH run at a scan rate of 50 mV sÀ1. The electrocat- groups on its surface. The higher electrocatalytic activity
alytic activity of methanol oxidation at the Pt/N-CNT of the nitrogen containing carbon nanotube supported
electrodes was evaluated and compared with that of electrode is due to higher dispersion and a good interac-
the conventional electrodes. During the anodic scan, tion between the support and the Pt particles The Vulcan
Fig. 4. EDX pattern of Pt/N-CNT electrode.
6. 910 T. Maiyalagan et al. / Electrochemistry Communications 7 (2005) 905–912
Fig. 5. Cyclic voltammograms of (a) pure Pt; (b) Pt/Vulcan (E-TEK) and (c) Pt/N-CNT in 1 M H2SO4/1 M CH3OH run at 50 mV sÀ1.
Table 1 also been reported [38]. All these results indicate that
Electrochemical parameters for methanol oxidation on the various the nitrogen functionality on CNT influences the
electrodes
catalytic activity of the catalyst. The enhanced electrocat-
Electrocatalyst Methanol oxidation Forward peak current alytic effect of the nitrogen containing carbon nanotube
onset potential (V) density (mA cmÀ2)
vs. Ag/AgCl
supported electrodes could also be partly due to the
following factors which require further investigation:
Bulk Pt 0.4 0.167
20% Pt/C (E-TEK) 0.45 1.3
(1) higher dispersion on the nitrogen containing carbon
Pt/N-CNT 0.22 13.3 nanotube support increases the availability of an
enhanced electrochemically active surface area, (2)
appearance of the specific active sites at the metal–
support boundary and, (3) strong metal–support
carbon support has randomly distributed pores of vary- interaction.
ing sizes which may make fuel and product diffusion Long-term stability is important for practical applica-
difficult whereas the tubular three-dimensional morphol- tions. Fig. 6 shows the current density–time plots of var-
ogy of the nitrogen containing carbon nanotubes makes ious electrodes in 1 M H2SO4 and 1 M CH3OH at 0.6 V.
the fuel diffusion easier. The Vulcan carbon contains high The performance of Pt electrodes was found to be poor
levels of sulfur (ca. 5000 ppm or greater), which could compared to the E-TEK and Pt/N-CNT electrode. The
potentially poison the fuel-cell electrocatalysts [37]. nitrogen containing carbon nanotube electrodes are the
Nitrogen containing carbon nanotubes used in this study most stable for direct methanol oxidation. The increas-
contains heterocyclic nitrogen so that it preferentially at- ing order of stability of various electrodes is; Pt < Pt/
taches the Pt particles. The selective attachment of Au Vulcan (E-TEK) < Pt/N-CNT. We are currently investi-
nanoparticles on nitrogen doped carbon nanotubes has gating whether nitrogen has a catalytic role that contrib-
7. T. Maiyalagan et al. / Electrochemistry Communications 7 (2005) 905–912 911
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