Practical Monolithic W, Mo Dual-Doped NiFeB Catalyst for Overall Water Splitting

Nickel–iron-based catalysts are considered promising candidates for low-cost electrocatalysts for water electrolysis. Nevertheless, their catalytic activities remain insufficient to meet the requirements for industrial-scale hydrogen production. Inspired by the satisfactory effects of cation doping and chemical etching in enhancing the catalytic performances of electrocatalysts, a Wo, Mo dual-doped monolithic NiFeB catalyst, NiFeWMoB 6 h, is fabricated via electroless plating and subsequent HCl etching. The catalyst requires only 94 and 254 mV to reach a current density of 100 mA cm–2 toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH. An anion exchange membrane water electrolyzer (AEMWE) with NiFeWMoB 6 h as both anode and cathode exhibits notable performance by requiring a low cell voltage of only 1.97 V to achieve 1 A cm–2 current density at 75 °C. Experimental results reveal that Mo6+ and W6+ function as Lewis acids and gain electrons from the Ni and Fe sites, resulting in optimized adsorption energies of oxygen-containing intermediates. Meanwhile, HCl etching effectively modifies the morphology of the NiFeWMoB 6 h catalyst and exposes abundant W and Mo species on the surface. Furthermore, the exposed W and Mo species play crucial roles in accelerating the reconstruction during the OER process and facilitating hydrogen adsorption for the HER. This study provides a comprehensive strategy for unlocking the potential of nickel–iron-based electrocatalysts for efficient water electrolysis.