ABSTRACT Efficient and durable bifunctional electrocatalysts are vital for scalable water electrolysis. Here, we realize cobalt‐vacancy (Co vac ) engineering in CoFeP supported on N,P‐codoped carbon nanocages (Co 1‐vac FeP/NPC) through a simple route comprising a CoFe Prussian blue analog precursor, phosphidation–pyrolysis, tannic‐acid etching, and a second phosphidation. Varying the tannic‐acid concentration tunes Co vac density. Density functional theory (DFT) shows that Co vac acts as a proton‐capture center in hydrogen evolution reaction (HER), accelerating OH − dissociation and lowering Δ G H *, while upshifting the d‐band center of neighboring Co in oxygen evolution reaction (OER) to weaken Co–O bonding and reduce the barrier of the rate‐determining step (*OH → *O). Benefiting from vacancy‐induced electronic modulation, the integrated FeP 4 /CoP 2 heterostructure, and the conductive NPC support, the optimized catalyst delivers overpotentials of 102 mV (HER) and 245 mV (OER) at 10 mA cm −2 in 1.0 M KOH, surpassing 20% Pt/C (120 mV) and RuO 2 (326 mV), respectively. A two‐electrode electrolyzer using the same catalyst at both electrodes requires only 1.555 V at 10 mA cm −2 and exhibits a cell‐voltage increase of just 7 mV after 24 h, outperforming a Pt/C||RuO 2 device. This work establishes a facile strategy to create metal‐cation vacancies and provides mechanistic guidance for designing multi‐vacancy heterostructure‐coupled catalysts for efficient alkaline water electrolysis.
Yuan et al. (Sat,) studied this question.