Enabling Internal Electric Field in Heterogeneous Nanosheets to Significantly Accelerate Alkaline Hydrogen Electrocatalysis.

Efficient bifunctional hydrogen electrocatalysis, encompassing both hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR), is of paramount significance in advancing hydrogen-based societies. While non-precious-metal-based catalysts, particularly those based on nickel (Ni), are essential for alkaline HER/HOR, their intrinsic catalytic activity often falls short of expectations. Herein, an internal electric field (IEF) strategy is introduced for the engineering of heterogeneous nickel-vanadium oxide nanosheet arrays grown on porous nickel foam (Ni-V 2 O 3 /PNF) as bifunctional electrocatalysts for hydrogen electrocatalysis. Strikingly, the Ni-V 2 O 3 /PNF delivers 10 mA cm -2 at an overpotential of 54 mV for HER and a mass-specific kinetic current of 19.3 A g -1 at an overpotential of 50 mV for HOR, placing it on par with the benchmark 20% Pt/C, while exhibiting enhanced stability in alkaline electrolytes. Density functional theory calculations, in conjunction with experimental characterizations, unveil that the interface IEF effect fosters asymmetrical charge distributions, which results in more thermoneutral hydrogen adsorption Gibbs free energy on the electron-deficient Ni side, thus elevating the overall efficiency of both HER and HOR. The discoveries reported herein guidance are provided for further understanding and designing efficient non-precious-metal-based electrocatalysts through the IEF strategy.