WO₃-Assisted Synergetic Effect Catalyzes Efficient and CO-Tolerant Hydrogen Oxidation for PEMFCs

Developing anode catalysts with substantially enhanced activity for hydrogen oxidation reaction (HOR) and CO tolerance performance is of great importance for the commercial applications of proton exchange membrane fuel cells (PEMFCs). Herein, an excellent CO-tolerant catalyst (Pd-WO₃/C) has been fabricated by loading Pd nanoparticles on WO₃ via an immersion-reduction route. A remarkably high power density of 1.33 W cm⁻² at 80 °C is obtained by using the optimized 3Pd-WO₃/C as the anode catalyst of PEMFCs, and the moderately reduced power density (73% remained) in CO/H₂ mixed gas can quickly recover after removal of CO-contamination from hydrogen fuel, which is not possible by using Pt/C or Pd/C as anode catalyst. The prominent HOR activity of 3Pd-WO₃/C is attributed to the optimized interfacial electron interaction, in which the activated H* adsorbed on Pd species can be effectively transferred to WO₃ species through hydrogen spillover effect and then oxidized through the H species insert/output effect during the formation of H_xWO₃ in acid electrolyte. More importantly, a novel synergetic catalytic mechanism about excellent CO tolerance is proposed, in which Pd and WO₃ respectively absorbs/activates CO and H₂O, thus achieving the CO electrooxidation and re-exposure of Pd active sites for CO-tolerant HOR.