Carbon-Free Pt Electrocatalysts Supported on SnO2 for Polymer Electrolyte Fuel Cells: Electrocatalytic Activity and Durability

The use of SnO2 as an alternative electrocatalyst support improves durability against voltage cycling up to a high potential, corresponding to the start-up and shut-down situation of polymer electrolyte fuel cell (PEFC) systems. Electrochemical surface area (ECSA) and oxygen reduction reaction (ORR) activity of Pt electrocatalysts as well as electrical conductivity of the electrocatalyst layers increase by doping of SnO2 with Nb or Sb. The durability tests with voltage cycles between 0.9 and 1.3 V versus reversible hydrogen electrode (RHE) potential have revealed that the Pt electrocatalyst supported on SnO2 (Pt/SnO2) withstands 60,000 voltage cycles while maintaining its ECSA, which corresponds to a lifetime of more than 20 years with respect to the durability against voltage cycling. These results indicate that SnO2-supported carbon-free electrocatalysts can be alternatives to the conventional Pt/C electrocatalyst, as a fundamental solution against carbon support corrosion, to improve PEFC durability.