Self-reconstruction of FeCoNiMoW high entropy alloy to boost OER activity with robust stability for anion exchange membrane water electrolyzer

Abstract

Anion exchange membrane water electrolysis (AEMWE) is a promising advanced strategy for large-scale green hydrogen production. Developing highly active, stable, and low-cost oxygen evolution reaction materials is still challenging. Herein, a core–shell FeCoNiMoW@FeCoNiOOH electrocatalyst was fabricated by in situ self-reconstruction of FeCoNiMoW high entropy alloy prepared via the fast carbothermal shock method. The surface Mo and W as sacrificing agents were etched in the reconstruction of the catalyst to generate more oxygen vacancies and form the FeCoNiOOH-rich medium entropy alloy shell, which is enriched in more active species M-OOH (i.e., NiOOH, CoOOH, FeOOH) to promote the OH adsorption. The medium/high entropy core–shell structure derived from self-reconstruction exhibited not only high activity but also excellent corrosion resistance, evidenced by an overpotential of 246 mV at 10 mA cm⁻² and a robust stability of 1000 h at 100 mA cm⁻². Moreover, this core–shell FeCoNiMoW@FeCoNiOOH-based anion exchange membrane water electrolyzer demonstrated a low cell voltage of 1.74 V to achieve a practical current density of 1 A cm⁻² and exhibited remarkable stability for 430 h with a decay rate of only 0.023 mV h⁻¹. This work provides guidance on designing cost-effective and outstanding corrosion-resistant OER electrocatalysts for anion exchange membrane water electrolysis.