Modulating Local Electronic Structure via Cluster Engineering on Cobalt Phosphide for Efficient Water/Seawater Splitting

Abstract Developing high‐performance, cost‐effective electrocatalysts for large‐scale water/seawater electrolysis is highly desirable, yet remains a significant challenge. Herein, oxidized iron nanocluster‐decorated cobalt phosphide (FeO x ‐ACs/Co x P) is designed and explored for water splitting. These oxidized iron nanoclusters provide an optimal thermodynamic environment that enhances electron‐transfer capability due to the Fe‐O‐Co bridge at the interface. They donate electrons to nearby Co and P sites, tuning their coordination environment and enhancing electron‐transfer capability. As a result, FeO x ‐ACs/Co x P exhibits outstanding oxygen evolution reaction (OER) performance with a low overpotential of 278 mV at 100 mA cm −2 and remarkable durability over 100 h at 100 mA cm −2 . Mechanism investigation reveals the formation of high‐valence Co active center and the optimized adsorbate evolution mechanism (AEM) pathway for OER. The formation of *O is identified as the rate‐determining step (RDS) for FeO x ‐ACs/Co x P with the lowest energy barrier. Moreover, FeO x ‐ACs/Co x P shows promise for alkaline natural seawater electrolysis, requiring only 298 mV at 100 mA cm −2 with over 100 h stability. An anion‐exchange membrane water electrolysis (AEM‐WE) device using FeO x ‐ACs/Co x P and Pt/C achieves a low voltage of 1.85 V at 500 mA cm −2 . This work demonstrates the potential of a precise nanocluster engineering strategy in enhancing the electrocatalytic performance for water splitting.