Constructing Built‐in Electric Field in Heterogeneous Nanowire Arrays for Efficient Overall Water Electrolysis

Efficient bifunctional electrocatalysts for hydrogen and oxygen evolution reactions are key to water electrolysis. Herein, we report built-in electric field (BEF) strategy to fabricate a heterogeneous nickel phosphide-cobalt nanowire arrays grown on carbon fiber paper (Ni2P-CoCH/CFP) with large work function difference (ΔΦ) as bifunctional electrocatalysts for overall splitting. Impressively, Ni2P-CoCH/CFP exhibits a remarkable catalytic activity for hydrogen and oxygen reactions to obtain 10 mA cm-2, respectively. Moreover, the fabricated lab-scale electrolyzer driven by an AAA battery delivers excellent stability after 50 h electrocatalysis with a 100% faradic efficiency. Computational calculations combining with experiments reveal the interface-induced electric field effect facilitates asymmetrical charge distributions, thereby regulating the adsorption/desorption of the intermediates during reactions. This work offers an avenue to rationally design high-performance heterogeneous electrocatalysts.