Polymer Electrolyte Fuel Cells Employing Heteropolyacids as Redox Mediators for Oxygen Reduction Reactions: Pt-Free Cathode Systems

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• 作者：Toshiaki Matsui ; Eri Morikawa ; Shintaro Nakada ; Takeou Okanishi ; Hiroki Muroyama ; Yoshifumi Hirao ; Tsuyoshi Takahashi ; Koichi Eguchi
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：July 20, 2016
• 年：2016
• 卷：8
• 期：28
• 页码：18119-18125
• 全文大小：467K
• 年卷期：0
• ISSN：1944-8252

文摘

In this study, the heteropolyacids of H_3+xPV_xMO_12–xO₄₀ (x = 0, 2, and 3) were applied as redox mediators for the oxygen reduction reaction in polymer electrolyte fuel cells, of which the cathode is free from the usage of noble metals such as Pt/C. In this system, the electrochemical reduction of heteropolyacid over the carbon cathode and the subsequent reoxidation of the partially reduced heteropolyacid by exposure to the dissolved oxygen in the regenerator are important processes for continuous power generation. Thus, the redox properties of catholytes containing these heteropolyacids were investigated in detail. The substitution quantity of V in the heteropolyacid affected the onset reduction potential as well as the reduction current density, resulting in a difference in cell performance. The chemical composition of heteropolyacid also had a significant impact on the reoxidation property. Among the three compounds, H₆PV₃Mo₉O₄₀ was the most suitable redox mediator. Furthermore, the pH of the catholyte was found to be the crucial factor in determining the reoxidation rate of partially reduced heteropolyacid as well as cell performance.