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Takeo Ohsaka - One of the best experts on this subject based on the ideXlab platform.
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Electrocatalytic oxidation of methanol at tantalum oxide-modified Pt Electrodes
Journal of Power Sources, 2012Co-Authors: Jahangir Masud, Muhammad Tanzirul Alam, Takeyoshi Okajima, Mohamed S. El-deab, Zaenal Awaludin, Takeo OhsakaAbstract:Abstract The current study addresses the electrocatalytic activity of tantalum oxide (TaOx)-modified Pt Electrode as a novel catalyst for methanol oxidation in acidic media. The modified Pt Electrode is shown to support a larger oxidation current of methanol compared to that obtained at the unmodified Pt Electrode concurrently with a favorable significant shift of the onset potential of methanol oxidation. Tafel plots, with a slope close to 0.118 V decade −1 , were obtained for methanol oxidation at the unmodified and TaOx-modified Pt Electrodes, reflecting that the methanol oxidation proceeds with the first electron transfer as the rate-determining step. The observed enhancement was attributed to a favorable d–d metal–metal oxide interaction which changes the electronic property of Pt and hence enhances the oxidation of the adsorbed reaction intermediates (e.g., CO ads ). Moreover, a possible contribution of the OH spillover via a so-called “bifunctional mechanism” is proposed. The influence of the temperature on the oxidation current of methanol at the TaOx-modified Pt Electrode is investigated and apparent activation energy, E a , for methanol oxidation is calculated as 39 kJ mol −1 at a specific potential. The proposed catalyst showed a good enhancement for methanol oxidation for a prolonged time of continuous potentiostatic electrolysis.
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Enhanced electrooxidation of formic acid at Ta2O5-modified Pt Electrode
Electrochemistry Communications, 2011Co-Authors: Jahangir Masud, Muhammad Tanzirul Alam, Rezwan Miah, Takeyoshi Okajima, Takeo OhsakaAbstract:A novel electrocatalyst, Ta2O5-modified Pt, for the oxidation of formic acid (HCOOH) was prepared by Electrodeposition of Ta on Pt Electrode from ionic liquid and the subsequent calcination. The modified Electrode shows an excellent electrocatalytic activity toward the direct oxidation of formic acid to CO2. The enhancement is attributed to the strong metal–oxide interaction between Pt and Ta2O5 as well as the OH− spillover effect of the Ta2O5-modified Pt Electrode, which greatly accelerates the electrooxidation of formic acid. The possible reaction mechanism is proposed.
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Temperature effect on the recovery of SO2-Poisoned GC/Nano-Pt Electrode towards oxygen reduction
Journal of Solid State Electrochemistry, 2010Co-Authors: Aboubakr M. Abdullah, Takeyoshi Okajima, Mahmoud M. Saleh, Mohamed I. Awad, Fusao Kitamura, Takeo OhsakaAbstract:The SO2 poisoning of Pt nanoparticle (n-Pt) modified glassy carbon (GC/n-Pt) Electrode and the recovery of its activity for the oxygen reduction reaction (ORR) were studied using cyclic voltammetry at ambient (25 °C) and elevated (70 °C) temperatures. Recovery of the GC/n-Pt Electrode by cycling the potential within the ORR range (1.0 to 0.2 V (standard hydrogen Electrode)) in 0.1 M H2SO4 was not effective at 25 °C, but at 70 °C the onset potential of the ORR was almost the same as that at the fresh GC/n-Pt Electrode. For the two different temperatures used here, the recovery on cycling the potential between 0.4 and 1.7 V was efficient. However, the number of cycles and the amount of charge required for the recovery at 70 °C were the smallest, which is of great interest for the proton exchange membrane fuel cell performance. The recovery using such a wide potential range at 70 °C resulted in an enhancement of the electrocatalytic activity of the GC/n-Pt Electrode over a non-poisoned (bare) GC/n-Pt Electrode.
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Hydrogen spillover phenomenon: Enhanced reversible hydrogen adsorPtion/desorPtion at Ta2O5-coated Pt Electrode in acidic media
Electrochimica Acta, 2010Co-Authors: Shunsuke Sata, Takeyoshi Okajima, Mohamed I. Awad, Mohamed S. El-deab, Takeo OhsakaAbstract:Abstract The current study is concerned with the preparation and characterization of tantalum oxide-loaded Pt (TaO x /Pt) Electrodes for hydrogen spillover application. XPS, SEM, EDX and XRD techniques are used to characterize the TaO x /Pt surfaces. TaO x /Pt Electrodes were prepared by galvanostatic Electrodeposition of Ta on Pt from LiF–NaF (60:40 mol%) molten salts containing K 2 TaF 7 (20 wt%) at 800 °C and then by annealing in air at various temperatures (200, 400 and 600 °C). The thus-fabricated TaO x /Pt Electrodes were compared with the non-annealed Ta/Pt and the unmodified Pt Electrodes for the hydrogen adsorPtion/desorPtion (H ads /H des ) reaction. The oxidation of Ta to the stoichiometric oxide (Ta 2 O 5 ) increases with increasing the annealing temperature as revealed from XPS and X-ray diffraction (XRD) measurements. The higher the annealing temperature the larger is the enhancement in the H ads /H des reaction at TaO x /Pt Electrode. The extraordinary increase in the hydrogen adsorPtion/desorPtion at the Electrode annealed at 600 °C is explained on the basis of a hydrogen spillover–reverse spillover mechanism. The hydrogen adsorPtion at the TaO x /Pt Electrode is a diffusion-controlled process.
Pei Kang Shen - One of the best experts on this subject based on the ideXlab platform.
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Methanol Electrochemical Oxidation on Au/Pt Electrode Enhanced by Phosphomolybdic Acid
The Journal of Physical Chemistry C, 2008Co-Authors: Yu Wang, Zidong Wei, Pei Kang Shen, Junpei Zhang, Hui ZhangAbstract:Methanol electro-oxidation was investigated on a Au-modified Pt (Au/Pt) Electrode together with phosphomolybdic acid (H3PMo12O40, PMo12). Au/Pt Electrode was prepared by chemically replacing underpotentially deposited Cu on Pt surface in HAuCl4 solution. The morphology of a Au/Pt Electrode was characterized by field emission scanning electron microscope. The results showed that Au particles with a mean size of 10 nm were uniformly dispersed on the Pt surface. The methanol electro-oxidation on the Pt Electrode was markedly enhanced not only by the phosphomolybdic acid solution but also by adatom Au. The onset potential of methanol oxidation shifts 400 mV toward the negative direction on the Au/Pt Electrode with phosphomolybdic acid in comparison with a Pt Electrode with phosphomolybdic acid. It is supposed that adsorbed hydrogen and intermediate CO from the methanol dehydrogenation and oxidation were electrocatalytically oxidized by the oxidant state of phosphomolybdic acid with the aid of Au catalysis.
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Electrooxidation of Methanol on upd-Ru and upd-Sn Modified Pt Electrodes
The journal of physical chemistry. B, 2006Co-Authors: Zidong Wei, Yi Luo, Chenglin Yan, C. X. Sun, G. Z. Yin, Pei Kang ShenAbstract:The electrochemical oxidation of methanol has been investigated on underpotentially deposited-ruthenium-modified platinum Electrode (upd-Ru/Pt) and on underpotentially deposited-tin-modified platinum Electrode (upd-Sn/Pt). The submonolayers of upd-Ru and upd-Sn on a Pt Electrode increased the rate of methanol electrooxidation several times as large as that on a pure Pt Electrode. The best performance for methanol electrooxidation was obtained on a ternary platinum based catalyst modified by upd-Ru and upd-Sn simultaneously. The influence of the submonolayers of upd-Ru adatoms and upd-Sn adatoms on the oxidation of methanol in acid has been investigated. The effect of Ru on methanol electrooxidation lies on the distribution of Ru adatoms on a Pt surface. It has been shown that as long as the amount of upd-Ru deposits were controlled in a proper range, upd-Ru deposits would enhance the methanol oxidation obtained on a Pt Electrode at whichever deposition potential the upd-Ru deposits were obtained. The effe...
Masatoshi Osawa - One of the best experts on this subject based on the ideXlab platform.
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hydrogen adsorPtion and hydrogen evolution reaction on a polycrystalline Pt Electrode studied by surface enhanced infrared absorPtion spectroscopy
Electrochimica Acta, 2007Co-Authors: Keiji Kunimatsu, Takahiro Senzaki, Gabor Samjeske, Minoru Tsushima, Masatoshi OsawaAbstract:Abstract Hydrogen evolution reaction (HER) on a polycrystalline Pt Electrode has been investigated in Ar-purged acids by surface-enhanced infrared absorPtion spectroscopy and electrochemical kinetic analysis (Tafel plot). A vibrational mode characteristic to H atom adsorbed at atop sites (terminal H) was observed at 2080–2095 cm−1. This band appears at 0.1 V (RHE) and grows at more negative potentials in parallel to the increase in hydrogen evolution current. Good signal-to-noise ratio of the spectra enabled us to establish the quantitative relation between the band intensity (equivalently, coverage) of terminal H and the kinetics of HER, from which we conclude that terminal H atom is the reaction intermediate in HER and the recombination of two terminal H atoms is the rate-determining step. The quantitative analysis of the infrared data also revealed that the adsorPtion of terminal H follows the Frumkin isotherm with repulsive interaction.
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in situ infrared spectroscopic and electrochemical study of hydrogen electro oxidation on Pt Electrode in sulfuric acid
Journal of Electroanalytical Chemistry, 2006Co-Authors: Keiji Kunimatsu, Masatoshi Osawa, Hiroyuki Uchida, Masahiro WatanabeAbstract:Abstract Intermediate and mechanism of electro-oxidation of hydrogen (HOR) on Pt Electrode was investigated in sulfuric acid solution under hydrogen atmosphere by in situ infrared spectroscopic method utilizing the ATR-SEIRAS (Surface Enhanced Infrared AbsorPtion Spectroscopy) mode. Adsorbed hydrogen species giving rise to infrared absorPtion band around 2090 cm −1 appears at ca. 0.1 V vs. RHE, developing its intensity at lower potentials. Dependence of its band intensity on overvoltage and H 2 partial pressure was analyzed based on the Volmer–Tafel mechanism of HOR with the rate determining dissociation of H 2 . Frumkin isotherm with a positive interaction parameter reproduced the observed dependence reasonably well assuming proportionality between coverage and band intensity of the adsorbed hydrogen. Further, the band intensity was found to be independent of sulfuric acid electrolyte concentration for a given overvoltage and hydrogen partial pressure, in agreement with the above mechanism. These results showed that the adsorbed hydrogen species detected is the intermediate of hydrogen evolution and oxidation on Pt, which is called overpotentially deposited hydrogen, H OPD .
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formate an active intermediate for direct oxidation of methanol on Pt Electrode
Journal of the American Chemical Society, 2003Co-Authors: Yanxia Chen, Atsushi Miki, Shen Ye, Hidetada Sakai, Masatoshi OsawaAbstract:The electro-oxidation of methanol on a Pt thin film Electrode in acidic solution has been investigated by in situ surface-enhanced IR absorPtion spectroscopy. A new IR peak is observed at around 1320 cm-1 when the Electrode potential is more positive than 0.5 V, where the bulk oxidation of MeOH occurs. This peak has been assigned to the symmetric stretching of formate species adsorbed on the Pt Electrode surface. It is the first observation of formate adsorPtion during the electro-oxidation of methanol on a Pt surface. A near proportional relationship between the intensity of the IR band of the formate species and MeOH electro-oxidation current is observed. A new reaction scheme via non-CO pathway with formate as the active intermediate is proposed for the methanol electro-oxidation process.
Kwang-yong Jee - One of the best experts on this subject based on the ideXlab platform.
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Sn Stability of Sn-Modified Pt Electrode for Reduction of Nitrate
Journal of The Electrochemical Society, 2007Co-Authors: Kwang-wook Kim, Seong Min Kim, Yeon-hwa Kim, Eil-hee Lee, Kwang-yong JeeAbstract:This work investigated the stability of a Sn-modified Pt Electrode for the reduction of nitrate using two type Electrodes prepared by adsorPtion or Electrodeposition of Sn onto Pt. In order to find the causes for the instability of the Electrode, the effects of the condition of the solutions in which the Electrode was used and the potential applied to the Electrode on the electrochemical and metallurgical behaviors of the Sn on the Pt Electrode were investigated. The Sn of the Sn-modified Pt Electrode existed as a Sn hydroxide form, which brought about an easy loss of the electroactivity of the Electrode in solution. During the reduction of nitrate, the electroactivity of the Electrode was affected by the potential applied to the Electrode. When a more negative potential than the redox potential between Sn(OH) 2 and Sn was applied, the Sn hydroxide was converted to Sn metal that was diffused into Pt, which led to a loss of electroactivity of the Electrode as well. The solid diffusion of Sn increased linearly with the applied potential. The Sn-Electrodeposited Pt Electrode was more favorable for maintaining the integrity of the Electrode during the electrolysis than the Sn-adsorbed Pt Electrode.
Takeyoshi Okajima - One of the best experts on this subject based on the ideXlab platform.
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Electrocatalytic oxidation of methanol at tantalum oxide-modified Pt Electrodes
Journal of Power Sources, 2012Co-Authors: Jahangir Masud, Muhammad Tanzirul Alam, Takeyoshi Okajima, Mohamed S. El-deab, Zaenal Awaludin, Takeo OhsakaAbstract:Abstract The current study addresses the electrocatalytic activity of tantalum oxide (TaOx)-modified Pt Electrode as a novel catalyst for methanol oxidation in acidic media. The modified Pt Electrode is shown to support a larger oxidation current of methanol compared to that obtained at the unmodified Pt Electrode concurrently with a favorable significant shift of the onset potential of methanol oxidation. Tafel plots, with a slope close to 0.118 V decade −1 , were obtained for methanol oxidation at the unmodified and TaOx-modified Pt Electrodes, reflecting that the methanol oxidation proceeds with the first electron transfer as the rate-determining step. The observed enhancement was attributed to a favorable d–d metal–metal oxide interaction which changes the electronic property of Pt and hence enhances the oxidation of the adsorbed reaction intermediates (e.g., CO ads ). Moreover, a possible contribution of the OH spillover via a so-called “bifunctional mechanism” is proposed. The influence of the temperature on the oxidation current of methanol at the TaOx-modified Pt Electrode is investigated and apparent activation energy, E a , for methanol oxidation is calculated as 39 kJ mol −1 at a specific potential. The proposed catalyst showed a good enhancement for methanol oxidation for a prolonged time of continuous potentiostatic electrolysis.
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Enhanced electrooxidation of formic acid at Ta2O5-modified Pt Electrode
Electrochemistry Communications, 2011Co-Authors: Jahangir Masud, Muhammad Tanzirul Alam, Rezwan Miah, Takeyoshi Okajima, Takeo OhsakaAbstract:A novel electrocatalyst, Ta2O5-modified Pt, for the oxidation of formic acid (HCOOH) was prepared by Electrodeposition of Ta on Pt Electrode from ionic liquid and the subsequent calcination. The modified Electrode shows an excellent electrocatalytic activity toward the direct oxidation of formic acid to CO2. The enhancement is attributed to the strong metal–oxide interaction between Pt and Ta2O5 as well as the OH− spillover effect of the Ta2O5-modified Pt Electrode, which greatly accelerates the electrooxidation of formic acid. The possible reaction mechanism is proposed.
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Temperature effect on the recovery of SO2-Poisoned GC/Nano-Pt Electrode towards oxygen reduction
Journal of Solid State Electrochemistry, 2010Co-Authors: Aboubakr M. Abdullah, Takeyoshi Okajima, Mahmoud M. Saleh, Mohamed I. Awad, Fusao Kitamura, Takeo OhsakaAbstract:The SO2 poisoning of Pt nanoparticle (n-Pt) modified glassy carbon (GC/n-Pt) Electrode and the recovery of its activity for the oxygen reduction reaction (ORR) were studied using cyclic voltammetry at ambient (25 °C) and elevated (70 °C) temperatures. Recovery of the GC/n-Pt Electrode by cycling the potential within the ORR range (1.0 to 0.2 V (standard hydrogen Electrode)) in 0.1 M H2SO4 was not effective at 25 °C, but at 70 °C the onset potential of the ORR was almost the same as that at the fresh GC/n-Pt Electrode. For the two different temperatures used here, the recovery on cycling the potential between 0.4 and 1.7 V was efficient. However, the number of cycles and the amount of charge required for the recovery at 70 °C were the smallest, which is of great interest for the proton exchange membrane fuel cell performance. The recovery using such a wide potential range at 70 °C resulted in an enhancement of the electrocatalytic activity of the GC/n-Pt Electrode over a non-poisoned (bare) GC/n-Pt Electrode.
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Hydrogen spillover phenomenon: Enhanced reversible hydrogen adsorPtion/desorPtion at Ta2O5-coated Pt Electrode in acidic media
Electrochimica Acta, 2010Co-Authors: Shunsuke Sata, Takeyoshi Okajima, Mohamed I. Awad, Mohamed S. El-deab, Takeo OhsakaAbstract:Abstract The current study is concerned with the preparation and characterization of tantalum oxide-loaded Pt (TaO x /Pt) Electrodes for hydrogen spillover application. XPS, SEM, EDX and XRD techniques are used to characterize the TaO x /Pt surfaces. TaO x /Pt Electrodes were prepared by galvanostatic Electrodeposition of Ta on Pt from LiF–NaF (60:40 mol%) molten salts containing K 2 TaF 7 (20 wt%) at 800 °C and then by annealing in air at various temperatures (200, 400 and 600 °C). The thus-fabricated TaO x /Pt Electrodes were compared with the non-annealed Ta/Pt and the unmodified Pt Electrodes for the hydrogen adsorPtion/desorPtion (H ads /H des ) reaction. The oxidation of Ta to the stoichiometric oxide (Ta 2 O 5 ) increases with increasing the annealing temperature as revealed from XPS and X-ray diffraction (XRD) measurements. The higher the annealing temperature the larger is the enhancement in the H ads /H des reaction at TaO x /Pt Electrode. The extraordinary increase in the hydrogen adsorPtion/desorPtion at the Electrode annealed at 600 °C is explained on the basis of a hydrogen spillover–reverse spillover mechanism. The hydrogen adsorPtion at the TaO x /Pt Electrode is a diffusion-controlled process.
