Preparation of Electrocatalysts for Polymer Electrolyte Fuel Cell Cathodes From Au Pt Core Shell Nanoparticles Synthesized by Simultaneous Aqueous Phase Reduction

Abstract

Electrocatalysts for polymer electrolyte fuel cell (PEFC) cathodes were prepared using AuPt coreshell nanoparticles. Polyvinylpyrrolidone (PVP)protected coreshell nanoparticles were synthesized by simultaneous aqueousphase reduction of Au and Pt, and they were deposited on carbon black support material. The catalyst powder was thermally processed in air to remove PVP, since the protecting polymers prevent nanoparticles from directly contacting the support material as well as reactant molecules. To avoid sintering during the thermal treatment, the effects of temperature and processing time on sintering were carefully examined. It was found that PVP was selectively oxidized and removed at 170 آ°C in air without notable damages to the other components of the catalyst. Stability of the coreshell catalyst in water was improved after the removal of PVP. The oxidation state of the Pt shell was found to be very close to zero. The thusprepared AuPt coreshell catalyst for a PEFC cathode exhibited mass activity that was 20% higher than that of pure Pt catalyst.