Discrepant roles of adsorbed OH* species on IrWO_x for boosting alkaline hydrogen electrocatalysis

Improving the slow kinetics of alkaline hydrogen electrode reactions, involving hydrogen oxidation and evolution reactions (HOR/HER) is highly desirable for accelerating the commercialization of alkaline exchange membrane-based fuel cells (AEMFCs) and water electrolyzers (AEMWEs). However, fundamental understanding of the mechanism for HOR/HER catalysis under alkaline media is still debatable. Here we develop an amorphous tungsten oxide clusters modified iridium-tungsten nanocrystallines (IrWO_x) which exhibited by far the highest exchange current density and mass activity, about three times higher than the commercial Pt/C toward alkaline HOR/HER. Density functional theory (DFT) calculations reveal the WO_x clusters act as a pivotal role to boost reversible hydrogen electrode reactions in alkaline condition but via different mechanisms, which are, hydrogen binding energy (HBE) mechanism for HOR and bi-functional mechanism for HER. This work is expected to promote our fundamental understanding about the alkaline HOR/HER catalysis and provide a new avenue for rational design of highly efficient electrocatalysts toward HOR/HER under alkaline electrolytes.