PtC- WO₃ electrocatalysts for degradation mitigation in polymer electrolyte fuel cells

Carbon-tungsten oxide (C- WO₃) and platinum/carbon-tungsten oxide (PtC- 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 PtC- WO₃ electrocatalysts produced ∼30% less hydrogen peroxide formation than baseline PtC. Membrane electrode assemblies (MEAs) were prepared using PtC and PtC- 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 ∼60% at the cathode condensate when PtC- WO₃ replaced PtC in the electrode. Fuel cell polarization data was obtained using PtC and PtC- 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 PtC- WO₃ was found to be lower than that of MEAs with PtC. 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.