Pt/C-WO3 electrocatalysts for degradation mitigation 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 similar to 60% less hydrogen peroxide than baseline C and Pt/C-WO3 electrocatalysts produced similar to 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 degrees C and 30% relative humidity (RH) at open circuit with hydrogen as fuel and oxygen as oxidant. The fluoride emission rate (in mu mol F-/h-cm(2)) over 24 h was found to be reduced by similar to 70% at the anode and similar to 60% 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 degrees 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. (c) 2008 The Electrochemical Society.