Enhancement of the Catalytic Activity and Load Cycle Durability of a PtCo Alloy Cathode Catalyst Supported on Ta-Doped SnO₂ with a Unique Fused Aggregated Network Microstructure for Polymer Electrolyte Fuel Cells

We succeeded in the synthesis of two types of PtCo alloy catalysts supported on Ta-doped SnO2 without using carbon black additives. The PtCo disordered alloy supported on Ta–SnO2 (BET surface area, 37 m2 g–1) with a unique fused-aggregate network microstructure was confirmed to show 3 times higher oxygen reduction reaction activity compared to that of a commercial Pt catalyst supported on carbon black (TEC10E50E, Tanaka Kikinzoku Co.) from the results of rotating disk electrode (RDE) measurements. PtCo alloy catalysts supported on Ta-doped SnO2 (PtCo/Ta–SnO2) that were heat-treated under reducing conditions for longer times formed a Pt-rich phase on the surface of the alloy catalyst. These PtCo/Ta–SnO2 catalysts with a Pt-rich surface phase exhibited more than 4 times higher kinetically controlled current density for the oxygen reduction reaction as well as a higher load cycle durability, in comparison with those of a commercial PtCo alloy catalyst supported on graphitized carbon black. PtCo/Ta–SnO2 catalysts with a Pt-rich surface phase are attractive candidates for polymer electrolyte fuel cell cathodes for fuel cell vehicles.