W-doping regulated the microenvironment of Ni2P@W-MoO2 composite electrocatalyst for driving ampere-level alkaline seawater splitting

Abstract

The rational construction of highly efficient electrocatalysts toward the hydrogen evolution reaction (HER) in alkaline electrolytes is critical for renewable energy technologies, but still challenging in seawater electrolysis at ampere-level current density. Herein, we design a nanoarray composite catalyst Ni₂P@W-MoO₂ through one-step hydrothermal and post-phosphidation, which shows excellent catalytic activity for hydrogen evolution in all alkaline, simulated seawater and seawater electrolytes at ampere-level current density, with low overpotentials of 328, 352 and 364 mV, respectively. Furthermore, an overall urea-assisted water splitting electrolyzer obtained by using Ni₂P@W-MoO₂ as the bifunctional catalyst can deliver a current density of 10 mA cm⁻² at a cell voltage of 1.36 V and operate stably for 100 h. In situ ATR-FTIR monitors the dynamic adsorption behavior of the important intermediate *OH on the surface of electrocatalysts. A series of density functional theory calculations further uncover the incorporation of W ameliorates the microenvironment of the MoO₂ and decreases the H₂O/*OH adsorption/dissociation energy barriers, simultaneously optimizing the H* Gibbes free energy on the Ni₂P, which achieves superior electrochemical water splitting performance. This work breaks through the proton-deficient dilemma of the alkaline HER at ampere-level current density and provides new insights into the design of cost-efficiency and environmentally friendly transition metal-based catalysts.