湿式素材プロセッシング（2）

[PY-64] Chemical reduction control of copper and platinum

○Tatsuichiro Nakamoto¹, Shuzo Tsuchida², Ryohei Seki², Yasuhiro Ueyama², Shun Yokoyama¹, Hideyuki Takahashi¹, Kazuyuki Tohji¹ (1. Tohoku University, 2. Panasonic Corporation)

Keywords:polymer electrolyte fuel cell, catalysts, Cu-Pt core-shell nanoparticles, chemical wet synthesis

Polymer electrolyte fuel cell (PEFC), which can provide clean electricity with high efficiency, is essential for improving the sustainability of our society. Since the oxygen reduction reaction (ORR) limits the performance of PEFC, precious platinum catalyst is crucial in the cathode electrode. Recently, Cu-Pt core-shell nanoparticles (NPs) have been synthesized to reduce the amount of Pt loading. Cu-Pt core-shell NPs are composed of inexpensive Cu for core and catalytically active Pt for shell. However, because oxidation-reduction potential (ORP) of Pt is usually much higher than that of Cu, Pt ions are easier to be reduced into metal and form the core, and the outer Cu will never show ORR activities. Therefore, in order to synthesize Cu-Pt core-shell NPs, it is necessary to control precipitation behavior of Cu and Pt. In this study, we developed an ORP calculation method to deduce a proper synthesis condition. However, ORP inversion of Cu and Pt was revealed to be effectively impossible, and controlling of chemical stabilities in aqueous solution was found to be insufficient to synthesize Cu-Pt core-shell NPs. Then, we examined solid Pt compound as starting material to delay the reduction reaction of Pt. Cu ions and Pt precipitates were injected as metal sources and chemically reduced together. Morphology of the sample was determined and ORR catalytic activities were evaluated.