Unique single‐phase electrocatalyst for excellent overall water splitting facilitated by multi‐atom synergistic effects

Abstract Hydrogen production via water electrolysis offers a sustainable pathway to decarbonize energy systems, yet the development of cost‐effective, efficient bifunctional electrocatalysts for overall water splitting (OWS) still remains a critical challenge. Current catalysts often rely on complex multiphase heterostructures to optimize oxygen and hydrogen evolution reactions (OER/HER), but their intricate designs increase costs and hinder scalability. Here, we present a single‐phase bifunctional electrocatalyst, CaCu 3 Co 2 Ru 2 O 12 (CCCRO), which exhibited exceptional performance for OWS in alkaline conditions, specifically, 1.536 V at 10 mA cm −2 and 1.629 V at 100 mA cm −2 , along with 500 h of operational stability at a current density of 100 mA cm −2 . In situ x‐ray absorption spectroscopy (XAS) revealed the valence‐state transition from Cu 2+ /Co 3+ /Ru 5+ to Cu 2+ /Co 3.5+ /Ru 5.5+ during OER, but both valence state reduction and structural reconstruction into a CuCoRu nanoalloy occurred under HER conditions. Density functional theory (DFT) calculations indicated that synergistic effects among Cu, Co, and Ru ions enhance catalytic activities for both OER and HER. This work demonstrates that structurally simple yet compositionally tuned oxides can surpass complex catalysts in both the efficiency and durability of OWS, offering a scalable design paradigm for advancing green hydrogen technologies. image