Now showing 1 - 10 of 10
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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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    Facile synthesis of triangular shaped palladium nanoparticles decorated nitrogen doped graphene and their catalytic study for renewable energy applications
    (19-02-2013)
    Vinayan, B. P.
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    We report a novel method for the synthesis of triangular shaped palladium nanoparticles (Pd NPs) decorated nitrogen doped graphene. Nitrogen doped graphene (N-G) is synthesized by uniform coating of polyelectrolyte modified graphene surface with a nitrogen containing polymer followed by their pyrolysis. The triangular shaped Pd NPs are decorated over nitrogen doped graphene (Pd/N-G) by kinetically controlling the polyol reduction process. The kinetic control of the growth of the nanoparticles and nitrogen doping of the supporting material leads to the formation of highly dispersed anisotropic nanoparticles over the graphene support. Hydrogen storage study of N-G and Pd/N-G give a storage capacity of 1.1 wt% and 1.9 wt%, respectively at 25 °C and 2 MPa hydrogen equilibrium pressure. Electrocatalytic study of Pd/N-G shows that it is a very good electrocatalyst for oxygen reduction reaction and highly stable in acidic media due to the strong binding between Pd NPs and graphene support as a result of nitrogen doping besides has high methanol tolerance in acidic media. The present synthesis procedure highlights a new pathway for the highly dispersed and different morphological metal nanoparticles decorated graphene composites for energy related applications. Copyright © 2012, Hydrogen Energy Publications, LLC.
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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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    1D-2D integrated hybrid carbon nanostructure supported bimetallic alloy catalyst for ethanol oxidation and oxygen reduction reactions
    (22-02-2019)
    Chandran, Priji
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    Puthusseri, Divya
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    Herein, 1-D carbon nanotubes and 2-D graphene hybrid carbon hetero-structure is employed as the catalyst support material for low temperature fuel cell. Partial unraveling of carbon nanotubes results in 1D-2D hybrid hetero-structure with enhanced surface area, while the intact inner tubes result in good electrical conductivity. Platinum-tin alloy decorated on partially exfoliated carbon nanotubes (Pt–Sn/PCNT) were prepared by ethylene glycol reduction method and investigated its electrocatalytic activity towards ethanol oxidation reaction (EOR) for direct ethanol fuel cell (DEFC) and oxygen reduction reaction (ORR) for hydrogen fuelled polymer electrolyte membrane fuel cell (PEMFC). Along with the intrinsic properties of carbon nanotubes, PCNT provides more anchoring sites, thereby facilitates complete utilization of catalysts. The electrochemical EOR studies reveal that Pt–Sn/PCNT has better tolerance to the accumulation of intermediate species than Pt–Sn/CNT. Besides, as-synthesized electrocatalysts exhibit good ORR activity with four-electron pathway. The enhanced EOR and ORR activity of as prepared electrocatalysts is attributed to the high dispersion of catalyst nanoparticles on PCNT along with the inhibition of production of intermediate species on the Pt surface by alloying. Further, the practical suitability of PCNT supported Pt–Sn nanocatalysts as EOR and ORR electrocatalysts has been examined by performing the full fuel cell measurements.
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    Platinum decorated on partially exfoliated multiwalled carbon nanotubes as high performance cathode catalyst for PEMFC
    (10-08-2015)
    Sahoo, Madhumita
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    Scott, Keith
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    We report a significant increase in the performance of a hybrid carbon structure of one dimensional (1D) multi-walled carbon nanotubes (MWNTs) and 2D graphene sheets as the catalyst support material for proton exchange membrane fuel cells. A few upper layers of multiwalled carbon nanotubes were cut open in the longitudinal direction to achieve a hybrid structure of opened up MWNTs as graphene "wings" attached to the unaffected inner tubes by modifying the chemical oxidation method followed by hydrogen induced reduction technique. These partially exfoliated nanotubes (PENTs) were used as the support material for Pt deposition using chemical reduction with ethylene glycol. These PENTs supported Pt catalysts were used for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). An enhanced performance of 1000 mW/cm2 compared to a cell with a commercial Pt/C (418 mW/cm2) was achieved which was attributed to the specific structure of the support material giving an improved effectual surface area as well as higher conductivity.
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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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    Optimizing metal-support interphase for efficient fuel cell oxygen reduction reaction catalyst
    (01-03-2020)
    Nechiyil, Divya
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    Garapati, Meenakshi Seshadhri
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    Shende, Rashmi Chandrabhan
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    Joulié, Sébastien
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    Neumeyer, David
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    Bacsa, Revathi
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    Puech, Pascal
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    Bacsa, Wolfgang
    The development of cost-effective and highly-efficient electro-catalysts is essential for the advancement of proton exchange membrane fuel cells (PEMFC). We present a novel nitrogen-sulphur co-doped carbon nanotubes-few layer graphene1D-2D hybrid support formed by partially exfoliating multiwall carbon nanotubes (PECNT), to improve interface bonding to catalyst nanoparticles. Detailed Raman spectroscopy and STEM-EDS analyses demonstrate that active sites on the co-doped hybrid support ensure both uniform distribution and improved bonding of the catalyst nanoparticles to the support. Electrochemical studies show that Pt nanoparticles decorated on nitrogen-sulphur co-doped PECNT (Pt/NS-PECNT) have higher electrochemical active surface area and mass activity accompanied by low H2O2 formation and improved positive half-wave potential, as compared to those decorated on co-doped rGO-incorporated PECNT hybrid structure (Pt/NS-(rGO-PECNT)). Fuel cell measurements demonstrate a higher power density for our novel (Pt/NS-PECNT) electro-catalyst when compared to both Pt/NS-(rGO + PECNT), and commercial Pt/C electro-catalyst. We demonstrate in this work that the interconnectivity between Pt-nanoparticles and the dopant or defect sites on the support play a crucial role in enhancing the ORR activity, fuel cell performance, and durability of the catalyst.
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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 graphene prepared by hydrothermal and thermal solid state methods as catalyst supports for fuel cell
    (06-04-2015)
    Jafri, R. Imran
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    Rajalakshmi, N.
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    Dhathathreyan, K. S.
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    Nitrogen doped graphene has been synthesized using hydrothermal method and thermal solid state method with ammonia and melamine as nitrogen sources respectively. Platinum nanoparticles have been dispersed over these support materials using polyol method and these Pt loaded nitrogen doped graphene samples have been studied as electrocatalyst for oxygen reduction reaction (ORR) in a proton exchange membrane fuel cell and for methanol oxidation reaction (MOR). Also, the role of multiwalled carbon nanotubes as a spacer which avoids face to face agglomeration of graphene sheets has also been studied for both the samples. The morphology and structure of the graphene based powder samples have been studied using X-ray diffraction, Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Half cell and full cell measurements have been performed on the samples for ORR and MOR. With the use of functionalized multiwalled carbon nanotubes, a maximum power density of 704 mW cm-2 and 650 mW cm-2 has been obtained with Pt dispersed nitrogen doped graphenes prepared by hydrothermal and thermal solid state methods respectively. The results have been compared with commercial Pt/C catalyst.
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    Nitrogen and sulfur co-doped porous carbon – is an efficient electrocatalyst as platinum or a hoax for oxygen reduction reaction in acidic environment PEM fuel cell?
    (01-01-2017)
    Sahoo, Madhumita
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    Non-precious, heteroatom doped carbon is reported to replace commercial Pt/C in both alkaline and acidic half-cell rotating disc electrode study; however the real world full cell measurements with the metal-free electrocatalysts overcoming the practical troubles in acidic environment proton exchange membrane fuel cell (PEMFC) are almost negligible to confirm the claim. Nitrogen and sulfur co-doped porous carbon (DPC) was synthesized in a one step, high yield process from single source ionic liquid precursor using eutectic salt as porogens to achieve porosity. Structural characterization confirms 7.03% nitrogen and 1.68% sulfur doping into the high surface area, porous carbon structure. As the cathode oxygen reduction reaction (ORR) catalyst, metal-free DPC and Pt nanoparticles decorated DPC (Pt/DPC) shows stable and high exchange current density by four electron transfer pathway in acidic half–cell liquid environment due to the synergistic effect of nitrogen and sulfur doping and porous nature of DPC. In an actual solid state full cell measurement, Pt/DPC shows higher performance comparable to commercial Pt/C; however DPC failed to reciprocate the half-cell performance due to blockage of active sites in the membrane electrode assembly fabrication process.