Pt/C catalyst impregnated with tungsten-oxide – Hydrogen oxidation reaction vs. CO tolerance

Abstract

Hydrogen Oxidation Reaction (HOR) is anode reaction in Proton exchange membrane fuel cells (PEMFCs) and it has very fast kinetics. However, the purity of fuel (H2) is very important and can slow down HOR kinetics, affecting the overall PEMFC performance. The performance of commercial Pt/C catalyst impregnated with WOx, as a catalyst for HOR, was investigated using a set of electrochemical methods (cyclic voltammetry, linear scan voltammetry and rotating disk electrode voltammetry). In order to deepen the understanding how WOx species can contribute CO tolerance of Pt/C, a particular attention was paid to CO poisoning. In the absence of CO, HOR is under diffusion limitations and HOR kinetics is not affected by WOx species. Appreciable HOR current on the electrodes pre-saturated with COads at potentials above 0.3 V vs. RHE, which is not observed for pure Pt/C, was discussed in details. HOR liming diffusion currents for higher concentrations of W are reached at high anodic potentials. The obtained results were explained by donation of OHads by WOx phase for COads removal in the mid potential region and reduced reactivity of Pt surface sites in the vicinity of the Pt|WOx interface. The obtained results can provide guidelines for development of novel CO tolerant PEMFC anode catalysts.