Now showing 1 - 10 of 10
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    Performance of polymer electrolyte membrane fuel cells with carbon nanotubes as oxygen reduction catalyst support material
    (02-02-2005)
    Rajalakshmi, N.
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    Ryu, Hojin
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    Shaijumon, M. M.
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    Platinum/carbon nanotubes (Pt/CNT) electrocatalysts are prepared. The CNTs are pre-treated in order to obtain reactive sites for the adherence of Pt metal particles. The electrocatalysts are characterized by scanning electron micrograph (SEM), transmission electron micrograph (TEM) and X-ray photoelectron spectrum (XPS) measurements. It is found that the catalysts contain both Pt(0) and Pt(IV) species. A high Pt loading of 32.5% on CNTs is obtained when the catalysts are prepared with ethylene glycol and Pt salt. The electrocatalysts are used for the oxygen reduction reaction in polymer electrolyte membrane fuel cells (PEMFCs) and the performance of PEMFC is analyzed with respect to catalyst synthesis and Pt loading. Cyclic voltammetric studies show that the Pt utilization in the fuel-cell electrodes is around 44%. Catalysts obtained with mild nitric acid-treated CNTs give a better performance of 680 mV at 500 mA cm-2 and 600 mV at 800 mA cm-2 than catalysts prepared with ethylene glycol and Pt salt. © 2004 Elsevier B.V. All rights reserved.
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    Functionalized 2D graphene sheets as catalyst support for proton exchange membrane fuel cell electrodes
    (31-05-2012)
    Karthika, P.
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    Rajalakshmi, N.
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    Imran Jaffri, R.
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    Dhathathreyan, K. S.
    Functionalized graphene sheets have been investigated as catalyst supports for platinum electrocatalysts for use in PEMFC electrodes. Well-dispersed Pt nanoparticles with small particle size were impregnated on graphene sheets. The electrochemical tests showed that the Pt nanoparticles supported on graphene shows good electrochemical activity and much higher Electrochemical Surface Area (ECSA) of 24 m 2/g. The maximum current density was found to be 700 mA/cm 2 for electrodes having Pt/G catalysts on both electrodes, compared to electrodes where Pt/C is being used at the anode. This study reveals that Pt/G can be a good electro catalyst not only for oxygen reduction but also for hydrogen oxidation. The dispersion of the electrocatalyst on graphene has been found to be useful for achieving relatively better performance in fuel cells. Electrochemical experiments show that the Pt supported on graphene oxide have superior catalytic performance indicating that the graphene may have a splendid future as catalyst carrier in electrocatalyst and fuel cell. © 2012 American Scientific Publishers All rights reserved.
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    Platinum on boron doped graphene as cathode electrocatalyst for proton exchange membrane fuel cells
    (24-08-2015)
    Pullamsetty, Ashok
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    Subbiah, Maheswari
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    Boron doped graphene (BG) has been prepared using a facile technique and platinum (Pt) nanoparticles has been deposited on BG using different methods like sodium borohydride, polyol and modified polyol reduction method and used as oxygen reduction reaction (ORR) electrocatalyst in hydrogen fuel cell. The identification of crystal phases through X-ray diffraction (XRD) and the dispersion of the electrocatalyst by the Transmission Electronic Microscopy (TEM) have been studied. The electrochemically active surface area has been investigated by Cyclic Voltammetry (CV). The ORR activity has been evaluated by polarization studies using fuel cell fixture. Stability test also conducted in fuel cell mode for 50 h. This study revealed the superior ORR activity and stability of platinum nanoparticles decorated BG, which is synthesized by modified polyol reduction technique. Hence it can be considered as the alternative electrocatalyst for replacing contemporary electrocatalysts.
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    Investigation of catalytic activity towards oxygen reduction reaction of Pt dispersed on boron doped graphene in acid medium
    (01-10-2016)
    Pullamsetty, Ashok
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    Boron doped graphene was prepared by a facile method and platinum (Pt) decoration over boron doped graphene was done in various chemical reduction methods such as sodium borohydride (NaBH4), polyol and modified polyol. X-ray diffraction analysis indicates that the synthesized catalyst particles are present in a nanocrystalline structure and transmission and scanning electron microscopy were employed to investigate the morphology and particle distribution. The electrochemical properties were investigated with the help of the rotating disk electrode (RDE) technique and cyclic voltammetry. The results show that the oxygen reduction reaction (ORR) takes place by a four-electron process. The kinetics of the ORR was evaluated using K-L and Tafel plots. The electrocatalyst obtained in modified polyol reduction method has shown the better catalytic activity compared to other two electrocatalysts.
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    Pt-Ru/multi-walled carbon nanotubes as electrocatalysts for direct methanol fuel cell
    (01-01-2008)
    Jha, Neetu
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    Leela Mohana Reddy, A.
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    Shaijumon, M. M.
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    Rajalakshmi, N.
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    Multi-walled carbon nanotubes (MWNTs) have been synthesized by hemical vapour deposition technique using AB3 alloy hydride catalyst and platinum supported MWNT (Pt/MWNT) and platinum-ruthenium supported MWNT (Pt-Ru/MWNT) electrocatalysts have been prepared by chemical reduction method. MWNT and electrocatalysts have been characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and energy dispersive X-ray analysis (EDX). The anode and cathode electrodes of direct methanol fuel cells (DMFC) have been fabricated using Pt-Ru/MWNT and 1:1 Pt / MWNT + Pt / C electrocatalyst, respectively. Performances of DMFC with these electrodes have been studied at different temperatures and the results have been discussed. A maximum power density of 39.3 mW / cm2 at a current density of 130 mA / cm2 has been obtained, which could be attributed to dispersion and accessibility of MWNT support and Pt-Ru in the electrocatalyst mixture for methanol oxidation reaction. © 2008 International Association for Hydrogen Energy.
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    Investigation of oxygen reduction and methanol oxidation reaction activity of PtAu nano-alloy on surface modified porous hybrid nanocarbon supports
    (01-09-2016)
    Vinayan, Bhaghavathi Parambath
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    Nagar, Rupali
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    Weinvestigate the electrocatalytic activity of PtAu alloy nanoparticles supported on various chemically modified carbon morphologies towards oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). The surface-modification of graphene nanosheets ( f-G), multi-walled carbon nanotubes ( f-MWNTs) and (graphene nanosheets-carbon nanotubes) hybrid support ( f-GMWNTs) were carried out by soft functionalization method using a cationic polyelectrolyte poly-(diallyldimethyl ammonium chloride). The Pt and PtAu alloy nanoparticles were dispersed over chemically modified carbon supports by sodium-borohydride assisted modified polyol reduction method. The electrochemical performance of all electrocatalysts were studied by half-and full-cell proton exchange membrane fuel cell (PEMFC) measurements and PtAu/f-G-MWNTs catalyst comparatively yielded the best catalytic performance. PEMFC full cell measurements of PtAu/f-GMWNTscathode electrocatalyst yield a maximum power density of 319mWcm2 at 60 °Cwithout any back pressure,which is 2.1 times higher than that of cathode electrocatalyst Pt on graphene support. The highORR andMORactivity of PtAu/f-G-MWNTs electrocatalyst is due to the alloying effect and inherent beneficial properties of porous hybrid nanocarbon support.
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    Oxygen reduction reaction activity of platinum nanoparticles decorated nitrogen doped carbon in proton exchange membrane fuel cell under real operating conditions
    (10-08-2016)
    Puthusseri, Divya
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    Nitrogen doping significantly improves the electrocatalytic activity of metal decorated carbon nanomaterials. Herein, nitrogen doped carbon (NC) is prepared by a facile method and platinum nanoparticles – decorated NC (Pt/NC) is prepared by polyol reduction technique. Pt/NC is applied as an efficient oxygen reduction reaction electrocatalyst in proton exchange membrane fuel cell. Membrane electrode assembly is fabricated with platinum decorated carbon as the anode electrocatalyst and Pt/NC as the cathode electrocatalyst. Both single cell measurement and stability study under fuel cell operating conditions reveal that Pt/NC is an alternative for replacing the conventional platinum–carbon composites.
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    Catalytic activity of platinum-cobalt alloy nanoparticles decorated functionalized multiwalled carbon nanotubes for oxygen reduction reaction in PEMFC
    (01-01-2012)
    Vinayan, B. P.
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    Jafri, R. Imran
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    Nagar, Rupali
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    Rajalakshmi, N.
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    The role of functionalized multiwalled carbon nanotubes (MWNTs) decorated with platinum nanoparticles (Pt/f-MWNTs) and platinum-cobalt alloy nanoparticles (Pt 3Co/f-MWNTs) has been investigated for oxygen reduction reaction (ORR) in a proton exchange membrane fuel cell. The electrocatalysts are synthesized by a conventional sodium borohydride reduction method and modified polyol reduction method. The modified polyol reduction method yields better uniform dispersion, higher loading and optimum particle size of Pt and Pt 3Co alloy nanoparticles over the MWNTs compared to the conventional sodium borohydride reduction method. The electrochemical surface area of the electrocatalysts is calculated using cyclic voltammetry. Pt 3Co/f- MWNTs synthesized via modified polyol reduction method yield the highest performance with a maximum power density of 798 mW cm -2 at 60 °C without any back pressure. The enhanced catalytic activity of Pt 3Co/f-MWNTs toward ORR is attributed to uniform dispersion and optimum particle size of Pt 3Co alloy nanoparticles over the surface of f-MWNTs. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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    Nitrogen-doped multi-walled carbon nanocoils as catalyst support for oxygen reduction reaction in proton exchange membrane fuel cell
    (03-08-2010)
    Jafri, R. Imran
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    Rajalakshmi, N.
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    Multi-walled carbon nanocoils (MWNCs) are synthesized by chemical vapour deposition and nitrogen-doped MWNCs (N-MWNCs) are obtained by nitrogen plasma treatment. MWNCs and N-MWNCs are used as catalyst supports for platinum nanoparticles. Pt nanoparticles are dispersed over these support materials using the conventional chemical reduction technique and then used for the oxygen reduction reaction in proton-exchange membrane fuel cells. The morphology and structure of the MWNC-based powder samples are studied by means of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Full cells are constructed with Pt-loaded MWNC/N-MWNC and the results are discussed. A maximum power density of 550 and 490 mW cm -2 is obtained with Pt/N-MWNC and Pt/MWNC as the ORR catalyst, respectively. The improved performance of a fuel cell with a N-MWNC catalyst support can be attributed to the creation of pyrrolic nitrogen defects due to the nitrogen plasma treatment. These defects act as good anchoring sites for the deposition of Pt nanoparticles and to the increased electrical conductivity and improved carbon-catalyst binding. © 2010 Elsevier B.V. All rights reserved.
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    Investigation of electrocatalytic activity of pt-y alloy nanoparticles dispersed on nitrogen doped graphene for proton exchange membrane fuel cell
    (01-09-2016)
    Ashok, P.
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    Divya, P.
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    Reduced graphene oxide (rGO) and nitrogen doped graphene (NG) have been used as a support for decorating the platinum (Pt) and yttrium (Y) alloy (Pt3Y) nanoparticles. Pt3Y nanoparticles decorated graphene (Pt3Y/G) and Pt3Y nanoparticles decorated nitrogen doped graphene (Pt3Y/NG) have been applied as oxygen reduction reaction (ORR) electrocatalysts in proton exchange membrane fuel cells. The electrochemically active surface area has been measured by Cyclic Voltammetry (CV). The ORR activity has been investigated by polarization studies using fuel cell fixture. The enhanced catalytic activity of Pt3Y/NG towards ORR is due to homogeneous dispersion and optimum particle size of Pt3Y alloy nanoparticles over the surface of NG. This study revealed that, Pt3Y/NG is more ORR active than Pt3Y/G.