Effects of tungsten oxide addition on the electrochemical performance of nanoscale tantalum oxide-based electrocatalysts for proton exchange membrane (PEM) fuel cells

► To improve the electrochemical performance of nanoscale tantalum oxide/carbon composite catalysts which are non-PGM catalysts for PEM fuel cells, tungsten was doped to alter the defect structure of tantalum oxide. ► Addition of tungsten to tantalum oxide led to the improvement in catalytic performance of tantalum oxide for oxygen reduction reaction, while maintaining high oxygen reduction onset potential comparable to Pt. ► The best catalysts with 32 mol% W showed specific current density up to 7% at 0.6 V and 35% at maximum current density at 2400 rpm compared to a commercial Pt/C catalyst. ► XPS analysis revealed that tungsten exists as 6+ in the Ta oxide (5+), indicating the creation of excess oxygen in tantalum oxide structure, which is possibly related to the improvement of catalytic performance of tantalum oxide mainly due to the reduction in resistance polarization. ► When loaded ∼5 times, the composite catalyst with 32 mol% W tested at 0.6 V reached ∼35% at 2400 rpm compared to the commercial Pt/C catalyst.