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Fujii K.,JX Nippon Oil and Energy Co. | Sato Y.,JX Nippon Oil and Energy Co. | Takase S.,Kyushu Institute of Technology | Shimizu Y.,Kyushu Institute of Technology
Journal of the Electrochemical Society | Year: 2014

A series of pyrochlore-type lead-ruthenium oxide (Pb2Ru2O7-δ) containing various amounts of oxygen vacancies was prepared by varying the heat-treatment temperature, and the oxygen reduction reaction (ORR) activity as well as the electrochemical redox property in acid and alkaline solution was evaluated using rotating disk electrode. The specific ORR activity was increased with increasing the amount of oxygen vacancies, and linearly correlated to the charge amount of electrochemical redox of Pb2Ru2O7-δ both in acid and alkaline solution. We concluded that the surface oxygen vacancy participates in the electrochemical redox of Pb2Ru2O7-δ, and at the same time, behaves as the active site for ORR. The ORR activity in alkaline solution was much higher than that in acid solution, possibly because of the difference of the facility of electrochemical desorption of adsorbed oxygen species in the ORR process. Additionally, the effect of humidity on the ORR activity was investigated by single cell test. It was revealed that Pb2Ru2O7-δ shows absolutely high ORR activity in dry condition. © The Author(s) 2014. Source


Fujii K.,JX Nippon Oil and Energy Co. | Ito M.,JX Nippon Oil and Energy Co. | Sato Y.,JX Nippon Oil and Energy Co. | Takenaka S.,Kyushu University | Kishida M.,Kyushu University
Journal of Power Sources | Year: 2014

Pd metal particles supported on a high surface area carbon black (Pd/CB) were covered with silica layers to improve the durability under severe cathode condition of proton exchange membrane fuel cells (PEMFCs). The performance and the durability of the silica-coated Pd/CB (SiO2/Pd/CB) were investigated by rotating disk electrode (RDE) in aqueous HClO4 and single cell test of the membrane-electrode assemblies (MEAs). SiO2/Pd/CB showed excellent durability exceeding Pt/CB during potential cycle in single cell test as well as in RDE measurement while Pd/CB significantly degraded. Furthermore, the MEA using SiO2/Pd/CB as the cathode catalyst showed higher performance than that using Pd/CB even in the initial state. The catalytic activity of SiO2/Pd/CB was higher than that of Pd/CB, and the drop of the cell performances due to the inhibition of electron conduction, proton conduction, and oxygen diffusion by the silica layer was not significant. It has been shown that the silica-coating is a very practical technique that can stabilize metal species originally unstable in the cathode condition of PEMFCs without a decrease in the cell performance. © 2015 Elsevier B.V. All rights reserved. Source

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