High Coverage Sub‐Nano Iridium Cluster on Core–Shell Cobalt‐Cerium Bimetallic Oxide for Highly Efficient Full‐pH Water Splitting

Abstract The construction of sub‐nanometer cluster catalysts (<1 nm) with almost complete exposure of active atoms serves as a promising avenue for the simultaneous enhancement of atom utilization efficiency and specific activity. Herein, a core–shell cobalt‐cerium bimetallic oxide protected by high coverage sub‐nanometer Ir clusters (denoted as Ir cluster@CoO/CeO 2 ) is constructed by a confined in situ exsolution strategy. The distinctive core–shell structure endows Ir cluster@CoO/CeO 2 with enhanced intrinsic activity and high conductivity, facilitating efficient charge transfer and full‐pH water splitting. The Ir cluster@CoO/CeO 2 achieves low overpotentials of 49/215, 52/390, and 54/243 mV at 10 mA cm −2 for hydrogen evolution reaction/oxygen evolution reaction (HER/OER) in 0.5 m H 2 SO 4 , 1.0 m PBS, and 1.0 m KOH, respectively. The small decline in performance after 300 h of operation renders it one of the most effective catalysts for full‐pH water splitting. DFT calculations indicate that oriented electron transfer (along the path from Ce to Co and then to Ir) creates an electron‐rich environment for surface Ir clusters. The reconstructed interface electronic environment provides optimized intermediates adsorption/desorption energy at the Ir site (for HER) and at the Ir‐Co site (for OER), thus simultaneously speeding up the HER/OER kinetics.