The Roles of Surface Hydrogen and Hydroxyl in Alkaline Hydrogen Oxidation on Ni-Based Electrocatalysts

One important target for anion exchange membrane fuel cells (AEMFCs) is to enable the application of anode non-precious metal hydrogen oxidation reaction (HOR) catalyst. Nickel presents a promising candidate for alkaline HOR; yet, its practical application is hampered by the intrinsically sluggish activity and poor stability. Herein, a series of Ni-based metals (Ni₅Mo, Ni₂₅Co, Ni₁₄W and Ni) are electrodeposited as model catalysts to systematically explore the alkaline HOR by considering the role of adsorbed hydroxyl (OH_ad). Spectroscopic studies together with density functional theory calculations shed light on the beneficial effect of transition metal M (M=Mo, Co, W) alloying/doping on HOR by introducing the charge transfer from M to Ni and down shifting Ni 3d band center. The HOR specific activities on Ni-based catalysts reveal a volcano-type relationship with the hydrogen binding energy (HBE). The strongly adsorbed OH_ad is proven to induce deactivation for Ni active sites, and the deactivation potential is OH_ad binding energy (OHBE) dependent. This study adds new insight into the HOR mechanism and stability of Ni-based electrocatalysts, providing a new avenue for the rational design of highly efficient and robust alkaline HOR catalysts.