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Atsushi Satsuma - One of the best experts on this subject based on the ideXlab platform.
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Enhancement of Alkaline Hydrogen Oxidation Reaction of Ru-Ir Alloy Nanoparticles through Bifunctional Mechanism on Ru-Ir Pair Site
ACS applied materials & interfaces, 2020Co-Authors: Kazutomo Ishikawa, Junya Ohyama, Keiichi Okubo, Kazumasa Murata, Atsushi SatsumaAbstract:Anion exchange membrane fuel cells (AEMFCs) are being developed for practical use. However, it is necessary to improve the Hydrogen Oxidation Reaction (HOR) under alkaline conditions to enhance the performance of AEMFCs. In this study, carbon-supported Ru-Ir alloy nanoparticle catalysts (Ru-Ir/C) were developed because they offer higher HOR activity compared with the Pt-based catalysts. The mechanism of HOR enhancement on Ru-Ir/C was studied to reveal the effect of the surface composition of Ru/Ir on the HOR activity. The results showed that the HOR activity is related to the surface pair probability of Ru-Ir, Ru-Ru, and Ir-Ir but not to the Hydrogen binding energy (HBE). In addition, the Ru-Ir pair site was found to be highly active, which can promote the HOR through a bifunctional mechanism that involves Ru-Ir pairs providing reactive OH- and H species, respectively.
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Surface modification of Pt nanoparticles with other metals boosting the alkaline Hydrogen Oxidation Reaction
Chemical communications (Cambridge England), 2019Co-Authors: Keiichi Okubo, Junya Ohyama, Atsushi SatsumaAbstract:To enhance the Hydrogen Oxidation Reaction (HOR) activity of Pt/C under alkaline conditions, the catalyst's surface was modified with fifteen metals. The surface modification enhanced the activity of Pt/C for the HOR beyond a change in Hydrogen binding energy (HBE), and this can be attributed to a change in the reactivity of surface oxygen species to adsorbed Hydrogen species.
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Improved Hydrogen Oxidation Reaction under alkaline conditions by ruthenium-iridium alloyed nanoparticles
Journal of Materials Chemistry A, 2016Co-Authors: Junya Ohyama, D. Kumada, Atsushi SatsumaAbstract:Carbon supported Ru–Ir (Ru–Ir/C) catalysts with their alloyed nanoparticles and those mainly having segregated Ru and Ir nanoparticles were prepared. The Ru–Ir alloyed nanoparticles improved the Hydrogen Oxidation Reaction (HOR) activity under alkaline conditions in comparison with the segregated Ru and Ir nanoparticles as well as Ru/C and Ir/C. Furthermore, the HOR activity of Ru–Ir alloyed nanoparticles was ca. four times higher than that of Pt/C. The cause of the enhanced HOR activity of Ru–Ir alloyed nanoparticles was investigated in terms of the Hydrogen-binding energy (HBE). It was found that the HOR activity increases with a decrease of the HBE, and Ru–Ir alloying lowers the HBE in comparison with the segregated Ru–Ir nanoparticles and Ir/C. Therefore, the lowered HBE by Ru–Ir alloying was considered to be responsible for the high HOR activity of Ru–Ir alloyed nanoparticles.
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size specifically high activity of ru nanoparticles for Hydrogen Oxidation Reaction in alkaline electrolyte
Journal of the American Chemical Society, 2013Co-Authors: Junya Ohyama, Yuta Yamamoto, Shigeo Arai, Takuma Sato, Atsushi SatsumaAbstract:The Hydrogen Oxidation Reaction (HOR) in alkaline electrolyte was conducted on carbon-supported Ru nanoparticles (Ru/C) of which size was controlled in the range from approximately 2 to 7 nm. The HOR activity of Ru/C normalized by the metal surface area showed volcano shaped dependence on the particle size with a maximum activity at approximately 3 nm. The HOR activity of approximately 3 nm Ru/C was higher than commercially available Pt nanoparticles (ca. 2 nm) supported on carbon. The structural analysis of Ru/C using Cs-corrected scanning transmission electron microscopy with atomic resolution revealed the unique structural change of Ru/C different from Pt/C: Ru nanoparticle structure changed from amorphous-like structure below 3 nm to metal nanocrystallite with roughened surface at approximately 3 nm and then to that with well-defined facets above 3 nm, although Pt/C kept well-defined facets even at approximately 2 nm. It is proposed that the generation of unique structure observed on approximately 3 n...
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Size Specifically High Activity of Ru Nanoparticles for Hydrogen Oxidation Reaction in Alkaline Electrolyte
Journal of the American Chemical Society, 2013Co-Authors: Junya Ohyama, Yuta Yamamoto, Shigeo Arai, Takuma Sato, Atsushi SatsumaAbstract:The Hydrogen Oxidation Reaction (HOR) in alkaline electrolyte was conducted on carbon-supported Ru nanoparticles (Ru/C) of which size was controlled in the range from approximately 2 to 7 nm. The HOR activity of Ru/C normalized by the metal surface area showed volcano shaped dependence on the particle size with a maximum activity at approximately 3 nm. The HOR activity of approximately 3 nm Ru/C was higher than commercially available Pt nanoparticles (ca. 2 nm) supported on carbon. The structural analysis of Ru/C using Cs-corrected scanning transmission electron microscopy with atomic resolution revealed the unique structural change of Ru/C different from Pt/C: Ru nanoparticle structure changed from amorphous-like structure below 3 nm to metal nanocrystallite with roughened surface at approximately 3 nm and then to that with well-defined facets above 3 nm, although Pt/C kept well-defined facets even at approximately 2 nm. It is proposed that the generation of unique structure observed on approximately 3 nm Ru nanoparticles, that is, long bridged coordinatively unsaturated Ru metal surface atoms on its nanocrystallite, is a key to achieve high HOR activity.
Young-uk Kwon - One of the best experts on this subject based on the ideXlab platform.
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Enhanced electrocatalytic performance for Hydrogen Oxidation Reaction on gold nanoparticles supported on tungsten oxide (VI) modified carbon
International Journal of Hydrogen Energy, 2012Co-Authors: Ji-hoon Jang, Eunjik Lee, Young-uk KwonAbstract:Abstract We report on a Hydrogen Oxidation Reaction (HOR) catalyst system composed of gold nanoparticles (Au NPs) and tungsten oxide (WO3). Previously, we reported that Au NPs could be activated for HOR by sonochemical heating and quenching. However, we also found that the activated Au NPs were poisoned by protons, the HOR product. In order to further improve the catalytic behavior of Au NPs, we employed tungsten oxide as a part of the support and a co-catalyst, by which proton spillover could be achieved. Au NPs supported on WO3/C were synthesized. The intermediates and final product were characterized by powder X-ray diffraction, energy dispersive X-ray spectroscopy, and transmission electron microscopy. Electrocatalytic activity of the samples for HOR was investigated by the linear sweep voltammetry with rotating disk electrode technique, which showed the disappearance of the proton poisoning of Au NPs in contact with WO3. Therefore, with sonication treatment, the Au NPs and WO3 composite showed a very high and stable activity for HOR.
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enhancement of electrocatalytic activity of platinum for Hydrogen Oxidation Reaction by sonochemically synthesized wc1 x nanoparticles
Journal of Power Sources, 2009Co-Authors: Juyeong Kim, Ji-hoon Jang, Yang-hee Lee, Young-uk KwonAbstract:Abstract Two types of composite materials composed of Pt and WC1−x nanoparticles supported on multiwalled carbon nanotubes (MWNT) are synthesized and evaluated in terms of their electrochemical properties, especially for the Hydrogen Oxidation Reaction (HOR). The Pt nanoparticles are prepared by reduction of H2PtCl6 with NaBH4, and the WC1−x nanoparticles by a sonochemical method with a W(CO)6 precursor. One of the composites is synthesized by forming WC1−x nanoparticles on Pt-loaded MWNT and the other by physically mixing Pt-loaded MWNT with WC1−x-loaded MWNT. The sonochemical synthesis of WC1−x on Pt-loaded MWNT forms WC1−x preferentially on Pt nanoparticles, which makes intimate contact between WC1−x and Pt nanoparticles. The cyclic voltammograms of these composite materials show evidences for H+-spill-over from Pt to WC1−x, thereby increasing the electrochemically active surface area (ECA). The composite in which WC1−x is deposited on Pt shows a remarkable increase in ECA probably because the intimate contact between WC1−x and Pt enhances the H+-spill-over. These materials exhibit enhanced HOR characteristics with Pt-specific mass activities about twice that of pure Pt nanoparticles.
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Sonochemical synthesis of tungsten carbide–palladium nanocomposites and their electrocatalytic activity for Hydrogen Oxidation Reaction
Electrochimica Acta, 2009Co-Authors: Ji-hoon Jang, Juyeong Kim, Yang-hee Lee, Chanho Pak, Young-uk KwonAbstract:Abstract Nanocomposites between β-WC and Pd nanoparticles supported on carbon are synthesized and their electrocatalytic properties for the Hydrogen Oxidation Reaction have been investigated. The Pd nanoparticles are obtained by a chemical reduction Reaction of PdCl 2 and the β-WC nanoparticles by a sonochemical decomposition of W(CO) 6 on Pd-loaded carbon followed by heat-treatment. Depending on the relative amounts of W to Pd, the Pd nanoparticles can be reacted with W to form Pd–W alloy nanoparticles. The Pd–W alloy, whose composition is estimated to have W less than 18 at.% based on its lattice parameter, lost most of the catalytic activity of Pd. On the other hand, the nanocomposite between β-WC and pure Pd shows an enhanced activity compared with that of Pd nanoparticles alone. This enhancement can be explained with the H + -spill-over to β-WC.
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Enhancement of electrocatalytic activity of platinum for Hydrogen Oxidation Reaction by sonochemically synthesized WC1−x nanoparticles
Journal of Power Sources, 2009Co-Authors: Juyeong Kim, Ji-hoon Jang, Yang-hee Lee, Young-uk KwonAbstract:Abstract Two types of composite materials composed of Pt and WC1−x nanoparticles supported on multiwalled carbon nanotubes (MWNT) are synthesized and evaluated in terms of their electrochemical properties, especially for the Hydrogen Oxidation Reaction (HOR). The Pt nanoparticles are prepared by reduction of H2PtCl6 with NaBH4, and the WC1−x nanoparticles by a sonochemical method with a W(CO)6 precursor. One of the composites is synthesized by forming WC1−x nanoparticles on Pt-loaded MWNT and the other by physically mixing Pt-loaded MWNT with WC1−x-loaded MWNT. The sonochemical synthesis of WC1−x on Pt-loaded MWNT forms WC1−x preferentially on Pt nanoparticles, which makes intimate contact between WC1−x and Pt nanoparticles. The cyclic voltammograms of these composite materials show evidences for H+-spill-over from Pt to WC1−x, thereby increasing the electrochemically active surface area (ECA). The composite in which WC1−x is deposited on Pt shows a remarkable increase in ECA probably because the intimate contact between WC1−x and Pt enhances the H+-spill-over. These materials exhibit enhanced HOR characteristics with Pt-specific mass activities about twice that of pure Pt nanoparticles.
Abel C. Chialvo - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of the kinetic parameters of the Hydrogen Oxidation Reaction on nanostructured iridium electrodes in alkaline solution
Journal of Electroanalytical Chemistry, 2016Co-Authors: María A. Montero, María R. Gennero De Chialvo, Abel C. ChialvoAbstract:Abstract The kinetic study of the Hydrogen Oxidation Reaction on a nanostructured iridium electrode was carried out in alkaline solution at different rotation rates. The electrode, prepared by sputtering on a glassy carbon substrate, was characterized by cyclic voltammetry, AFM and XPS techniques. Then, the experimental current density ( j ) vs. overpotential ( η ) curves were recorded in the range comprised between − 0.015 ≤ η /V ≤ 0.30. The correlation of the resulting curves was carried out considering the Tafel-Heyrovsky-Volmer mechanism, with a Frumkin type isotherm for the adsorption of the Reaction intermediate. The kinetic parameters (equilibrium Reaction rates of the elementary steps and surface coverage of the adsorbed Hydrogen) were evaluated. The results obtained indicate that, in the potential range evaluated, the Reaction takes place mainly through the Tafel-Volmer route with a small contribution of the Heyrovsky-Volmer route. Finally, an explanation for the lower electrocatalytic activity observed in alkaline solutions with respect to that in acid solutions was proposed, on the basis of the movement restrictions of the hydroxyl ion inside the superficial water network to make possible the electron transference in the Volmer and Heyrovsky steps.
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Kinetics of the Hydrogen Oxidation Reaction on nanostructured rhodium electrodes in alkaline solution
Journal of Power Sources, 2015Co-Authors: María A. Montero, María R. Gennero De Chialvo, Abel C. ChialvoAbstract:Abstract The Hydrogen Oxidation Reaction was studied on a nanostructured rhodium electrode at different rotation rates in alkaline solution. The electrode was prepared via sputtering on a glassy carbon disc support and it was characterized by atomic force microscopy and cyclic voltammetry. The real surface area was evaluated by CO stripping voltammetry. Experimental current density ( j ) – overpotential ( η ) curves of the Hydrogen Oxidation Reaction were obtained in the range −0.015 ≤ η /V ≤ 0.40 at different rotation rates (900 ≤ ω /rpm ≤ 4900). The resulting curves were correlated by kinetic expressions derived from the Tafel-Heyrovsky-Volmer mechanism with a Frumkin type adsorption of the Reaction intermediate and the kinetic parameters were evaluated. It was verified that over this overpotential region the Reaction in alkaline solution proceeds mainly through the Tafel-Volmer route. These results were compared with those previously obtained in acid solutions.
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Criteria for the selection of the scan rate in the evaluation of the kinetic parameters of the Hydrogen Oxidation Reaction by a potentiodynamic sweep
Journal of Electroanalytical Chemistry, 2015Co-Authors: C.a. Marozzi, María R. Gennero De Chialvo, Abel C. ChialvoAbstract:Abstract The use of the current density values obtained from a voltammetric sweep at a slow scan rate j vs ( η ) in place of those of a steady state polarization j ss ( η ) for the determination of the kinetic parameters of the Hydrogen Oxidation Reaction ( hor ) on a rotating disk electrode was analyzed. Three sets of kinetic parameters similar to those evaluated previously for the noble metals Pt, Ir and Rh, used as electrocatalysts for this Reaction, at three different rotation rates ω (100, 3600 and 10,000 rpm) and four different scan rates v s (10 −4 , 10 −3 , 10 −2 and 5 × 10 −2 V s −1 ) were selected for this study. The determination of the Hydrogen electrode Reaction (HER) polarization resistance, around the equilibrium condition, was also investigated. Finally, the conditions in which the approximation j vs ( η ) ≅ j ss ( η ) can be considered valid were established for both, the polarization plot and the polarization resistance and practical criteria were established.
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Characterization and kinetic study of a nanostructured rhodium electrode for the Hydrogen Oxidation Reaction
Journal of Power Sources, 2014Co-Authors: María A. Montero, María R. Gennero De Chialvo, José L. Fernández, Abel C. ChialvoAbstract:Abstract The Hydrogen Oxidation Reaction was studied on a nanostructured rhodium electrode at different rotation rates. The electrode was prepared via sputtering on a glassy carbon disc support and it was characterized by X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and cyclic voltammetry, which allowed verifying the nanostructured morphology and the absence of any phase other than metallic rhodium. The real surface area was evaluated by CO stripping voltammetry. Experimental current density ( j ) – overpotential ( η ) curves of the Hydrogen Oxidation Reaction were obtained in the range −0.015 V ≤ η ≤ 0.25 V at different rotation rates in sulphuric acid solution. They were correlated by kinetic expressions derived from the Tafel–Heyrovsky–Volmer mechanism and thus the kinetic parameters were evaluated. It was verified that over this overpotential region the Reaction proceeds through the simultaneous occurrence of the Tafel–Volmer and the Heyrovsky–Volmer route.
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Kinetic Study of the Hydrogen Oxidation Reaction on Nanostructured Iridium Electrodes in Acid Solutions
The Journal of Physical Chemistry C, 2013Co-Authors: M. Angeles Montero, José L. Fernández, M. Rosa Gennero De Chialvo, Abel C. ChialvoAbstract:The Hydrogen Oxidation Reaction was studied on a rotating disc electrode of nanostructured iridium supported on glassy carbon. The electrode was prepared via sputtering and further annealing at 400 °C under a Hydrogen atmosphere to avoid the presence of iridium oxide. The iridium film was analyzed by microscopic (scanning electron microscopy (SEM), atomic force microscopy (AFM)), spectroscopic (X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS)), and electrochemical (cyclic voltammetry) techniques, which allowed us to verify the nanostructured morphology and the absence of any phase other than metallic iridium. The real surface area was evaluated by adsorption of underpotential deposition (UDP) Hydrogen and CO stripping. Experimental current–overpotential (η) curves of the Hydrogen Oxidation Reaction were obtained in the range −0.03 V ≤ η ≤ 0.20 V at different rotation rates in sulfuric acid solution. They were correlated by kinetic expressions, and the corresponding values of the kinetic ...
Junya Ohyama - One of the best experts on this subject based on the ideXlab platform.
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Enhancement of Alkaline Hydrogen Oxidation Reaction of Ru-Ir Alloy Nanoparticles through Bifunctional Mechanism on Ru-Ir Pair Site
ACS applied materials & interfaces, 2020Co-Authors: Kazutomo Ishikawa, Junya Ohyama, Keiichi Okubo, Kazumasa Murata, Atsushi SatsumaAbstract:Anion exchange membrane fuel cells (AEMFCs) are being developed for practical use. However, it is necessary to improve the Hydrogen Oxidation Reaction (HOR) under alkaline conditions to enhance the performance of AEMFCs. In this study, carbon-supported Ru-Ir alloy nanoparticle catalysts (Ru-Ir/C) were developed because they offer higher HOR activity compared with the Pt-based catalysts. The mechanism of HOR enhancement on Ru-Ir/C was studied to reveal the effect of the surface composition of Ru/Ir on the HOR activity. The results showed that the HOR activity is related to the surface pair probability of Ru-Ir, Ru-Ru, and Ir-Ir but not to the Hydrogen binding energy (HBE). In addition, the Ru-Ir pair site was found to be highly active, which can promote the HOR through a bifunctional mechanism that involves Ru-Ir pairs providing reactive OH- and H species, respectively.
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Surface modification of Pt nanoparticles with other metals boosting the alkaline Hydrogen Oxidation Reaction
Chemical communications (Cambridge England), 2019Co-Authors: Keiichi Okubo, Junya Ohyama, Atsushi SatsumaAbstract:To enhance the Hydrogen Oxidation Reaction (HOR) activity of Pt/C under alkaline conditions, the catalyst's surface was modified with fifteen metals. The surface modification enhanced the activity of Pt/C for the HOR beyond a change in Hydrogen binding energy (HBE), and this can be attributed to a change in the reactivity of surface oxygen species to adsorbed Hydrogen species.
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Improved Hydrogen Oxidation Reaction under alkaline conditions by ruthenium-iridium alloyed nanoparticles
Journal of Materials Chemistry A, 2016Co-Authors: Junya Ohyama, D. Kumada, Atsushi SatsumaAbstract:Carbon supported Ru–Ir (Ru–Ir/C) catalysts with their alloyed nanoparticles and those mainly having segregated Ru and Ir nanoparticles were prepared. The Ru–Ir alloyed nanoparticles improved the Hydrogen Oxidation Reaction (HOR) activity under alkaline conditions in comparison with the segregated Ru and Ir nanoparticles as well as Ru/C and Ir/C. Furthermore, the HOR activity of Ru–Ir alloyed nanoparticles was ca. four times higher than that of Pt/C. The cause of the enhanced HOR activity of Ru–Ir alloyed nanoparticles was investigated in terms of the Hydrogen-binding energy (HBE). It was found that the HOR activity increases with a decrease of the HBE, and Ru–Ir alloying lowers the HBE in comparison with the segregated Ru–Ir nanoparticles and Ir/C. Therefore, the lowered HBE by Ru–Ir alloying was considered to be responsible for the high HOR activity of Ru–Ir alloyed nanoparticles.
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size specifically high activity of ru nanoparticles for Hydrogen Oxidation Reaction in alkaline electrolyte
Journal of the American Chemical Society, 2013Co-Authors: Junya Ohyama, Yuta Yamamoto, Shigeo Arai, Takuma Sato, Atsushi SatsumaAbstract:The Hydrogen Oxidation Reaction (HOR) in alkaline electrolyte was conducted on carbon-supported Ru nanoparticles (Ru/C) of which size was controlled in the range from approximately 2 to 7 nm. The HOR activity of Ru/C normalized by the metal surface area showed volcano shaped dependence on the particle size with a maximum activity at approximately 3 nm. The HOR activity of approximately 3 nm Ru/C was higher than commercially available Pt nanoparticles (ca. 2 nm) supported on carbon. The structural analysis of Ru/C using Cs-corrected scanning transmission electron microscopy with atomic resolution revealed the unique structural change of Ru/C different from Pt/C: Ru nanoparticle structure changed from amorphous-like structure below 3 nm to metal nanocrystallite with roughened surface at approximately 3 nm and then to that with well-defined facets above 3 nm, although Pt/C kept well-defined facets even at approximately 2 nm. It is proposed that the generation of unique structure observed on approximately 3 n...
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Size Specifically High Activity of Ru Nanoparticles for Hydrogen Oxidation Reaction in Alkaline Electrolyte
Journal of the American Chemical Society, 2013Co-Authors: Junya Ohyama, Yuta Yamamoto, Shigeo Arai, Takuma Sato, Atsushi SatsumaAbstract:The Hydrogen Oxidation Reaction (HOR) in alkaline electrolyte was conducted on carbon-supported Ru nanoparticles (Ru/C) of which size was controlled in the range from approximately 2 to 7 nm. The HOR activity of Ru/C normalized by the metal surface area showed volcano shaped dependence on the particle size with a maximum activity at approximately 3 nm. The HOR activity of approximately 3 nm Ru/C was higher than commercially available Pt nanoparticles (ca. 2 nm) supported on carbon. The structural analysis of Ru/C using Cs-corrected scanning transmission electron microscopy with atomic resolution revealed the unique structural change of Ru/C different from Pt/C: Ru nanoparticle structure changed from amorphous-like structure below 3 nm to metal nanocrystallite with roughened surface at approximately 3 nm and then to that with well-defined facets above 3 nm, although Pt/C kept well-defined facets even at approximately 2 nm. It is proposed that the generation of unique structure observed on approximately 3 nm Ru nanoparticles, that is, long bridged coordinatively unsaturated Ru metal surface atoms on its nanocrystallite, is a key to achieve high HOR activity.
Ji-hoon Jang - One of the best experts on this subject based on the ideXlab platform.
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Enhanced electrocatalytic performance for Hydrogen Oxidation Reaction on gold nanoparticles supported on tungsten oxide (VI) modified carbon
International Journal of Hydrogen Energy, 2012Co-Authors: Ji-hoon Jang, Eunjik Lee, Young-uk KwonAbstract:Abstract We report on a Hydrogen Oxidation Reaction (HOR) catalyst system composed of gold nanoparticles (Au NPs) and tungsten oxide (WO3). Previously, we reported that Au NPs could be activated for HOR by sonochemical heating and quenching. However, we also found that the activated Au NPs were poisoned by protons, the HOR product. In order to further improve the catalytic behavior of Au NPs, we employed tungsten oxide as a part of the support and a co-catalyst, by which proton spillover could be achieved. Au NPs supported on WO3/C were synthesized. The intermediates and final product were characterized by powder X-ray diffraction, energy dispersive X-ray spectroscopy, and transmission electron microscopy. Electrocatalytic activity of the samples for HOR was investigated by the linear sweep voltammetry with rotating disk electrode technique, which showed the disappearance of the proton poisoning of Au NPs in contact with WO3. Therefore, with sonication treatment, the Au NPs and WO3 composite showed a very high and stable activity for HOR.
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enhancement of electrocatalytic activity of platinum for Hydrogen Oxidation Reaction by sonochemically synthesized wc1 x nanoparticles
Journal of Power Sources, 2009Co-Authors: Juyeong Kim, Ji-hoon Jang, Yang-hee Lee, Young-uk KwonAbstract:Abstract Two types of composite materials composed of Pt and WC1−x nanoparticles supported on multiwalled carbon nanotubes (MWNT) are synthesized and evaluated in terms of their electrochemical properties, especially for the Hydrogen Oxidation Reaction (HOR). The Pt nanoparticles are prepared by reduction of H2PtCl6 with NaBH4, and the WC1−x nanoparticles by a sonochemical method with a W(CO)6 precursor. One of the composites is synthesized by forming WC1−x nanoparticles on Pt-loaded MWNT and the other by physically mixing Pt-loaded MWNT with WC1−x-loaded MWNT. The sonochemical synthesis of WC1−x on Pt-loaded MWNT forms WC1−x preferentially on Pt nanoparticles, which makes intimate contact between WC1−x and Pt nanoparticles. The cyclic voltammograms of these composite materials show evidences for H+-spill-over from Pt to WC1−x, thereby increasing the electrochemically active surface area (ECA). The composite in which WC1−x is deposited on Pt shows a remarkable increase in ECA probably because the intimate contact between WC1−x and Pt enhances the H+-spill-over. These materials exhibit enhanced HOR characteristics with Pt-specific mass activities about twice that of pure Pt nanoparticles.
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Sonochemical synthesis of tungsten carbide–palladium nanocomposites and their electrocatalytic activity for Hydrogen Oxidation Reaction
Electrochimica Acta, 2009Co-Authors: Ji-hoon Jang, Juyeong Kim, Yang-hee Lee, Chanho Pak, Young-uk KwonAbstract:Abstract Nanocomposites between β-WC and Pd nanoparticles supported on carbon are synthesized and their electrocatalytic properties for the Hydrogen Oxidation Reaction have been investigated. The Pd nanoparticles are obtained by a chemical reduction Reaction of PdCl 2 and the β-WC nanoparticles by a sonochemical decomposition of W(CO) 6 on Pd-loaded carbon followed by heat-treatment. Depending on the relative amounts of W to Pd, the Pd nanoparticles can be reacted with W to form Pd–W alloy nanoparticles. The Pd–W alloy, whose composition is estimated to have W less than 18 at.% based on its lattice parameter, lost most of the catalytic activity of Pd. On the other hand, the nanocomposite between β-WC and pure Pd shows an enhanced activity compared with that of Pd nanoparticles alone. This enhancement can be explained with the H + -spill-over to β-WC.
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Enhancement of electrocatalytic activity of platinum for Hydrogen Oxidation Reaction by sonochemically synthesized WC1−x nanoparticles
Journal of Power Sources, 2009Co-Authors: Juyeong Kim, Ji-hoon Jang, Yang-hee Lee, Young-uk KwonAbstract:Abstract Two types of composite materials composed of Pt and WC1−x nanoparticles supported on multiwalled carbon nanotubes (MWNT) are synthesized and evaluated in terms of their electrochemical properties, especially for the Hydrogen Oxidation Reaction (HOR). The Pt nanoparticles are prepared by reduction of H2PtCl6 with NaBH4, and the WC1−x nanoparticles by a sonochemical method with a W(CO)6 precursor. One of the composites is synthesized by forming WC1−x nanoparticles on Pt-loaded MWNT and the other by physically mixing Pt-loaded MWNT with WC1−x-loaded MWNT. The sonochemical synthesis of WC1−x on Pt-loaded MWNT forms WC1−x preferentially on Pt nanoparticles, which makes intimate contact between WC1−x and Pt nanoparticles. The cyclic voltammograms of these composite materials show evidences for H+-spill-over from Pt to WC1−x, thereby increasing the electrochemically active surface area (ECA). The composite in which WC1−x is deposited on Pt shows a remarkable increase in ECA probably because the intimate contact between WC1−x and Pt enhances the H+-spill-over. These materials exhibit enhanced HOR characteristics with Pt-specific mass activities about twice that of pure Pt nanoparticles.
