Pt/C-WO3 Electrocatalysts for Degradation Mitigation 1 in Polymer Electrolyte Fuel Cells.

Carbon-tungsten oxide (C-WO₃) and platinum/carbon-tungsten oxide (Pt/C-WO₃) catalysts were prepared by chemical methods. The WO₃ loading in the catalyst was 15 wt %. C-WO₃ catalysts produced ∼60% less hydrogen peroxide than baseline C and Pt/C-WO₃ electrocatalysts produced ∼30% less hydrogen peroxide formation than baseline Pt/C. Membrane electrode assemblies (MEAs) were prepared using Pt/C and Pt/C-WO₃ electrocatalysts and subjected to accelerated durability tests at 90°C and 30% relative humidity (RH) at open circuit with hydrogen as fuel and oxygen as oxidant. The fluoride emission rate (in μmol F^-/h-cm²) over 24 h was found to be reduced by ∼70% at the anode and ²60% at the cathode condensate when Pt/C-WO₃ replaced Pt/C in the electrode. Fuel cell polarization data was obtained using Pt/C and Pt/C-WO₃ in the cathode at 80°C and 75, 50, and 25% RH, with air and oxygen as oxidants and hydrogen as fuel. For all the test conditions, the performance of MEAs with Pt/C-WO₃ was found to be lower than that of MEAs with Pt/C. Through electrochemical impedance spectroscopy experiments and polarization data analysis, the lower performance was attributed to (i) lower catalytic activity, and (ii) higher ionic and transport resistances in the electrodes. [ABSTRACT FROM AUTHOR]