Constructing IEF‐Induced Tetrahedral Co Sites to Regulate Interfacial Hydrogen Bonding Network for Enhanced Oxygen Evolution

ABSTRACT The optimization of interfacial hydrogen bonding network structure is paramount to achieve efficient alkaline oxygen evolution reaction (OER). Herein, we successfully modulated CoN with octahedral ( O h ) Co 2+ sites into CoN/HfO 2 with tetrahedral ( T d ) Co 2+ by the internal electric field (IEF) strategy to regulate interfacial water activity and enhance the alkaline OER activity. The CoN/HfO 2 catalyst exhibits excellent OER performance (251 mV@10 mA cm −2 ). Furthermore, an electrolyzer assembled with CoN/HfO 2 achieves high current densities at low voltages. Simultaneously, the application of CoN/HfO 2 in practical solar‐driven water splitting system processes high and stable solar‐to‐hydrogen efficiency of 14.16% without bias voltage. The results elucidate that the IEF induces ligand field distortion, creating active T d Co 2+ sites whose incompletely occupied t 2 single‐spin electronic configuration. Their specific electronic configuration facilitates interaction with the hydroxylated surface and easier formation of reactive CoOOH species. Crucially, this process reorganizes the interfacial water structure. The hydrogen bonding between the T d Co 2+ sites and water promote a high local concentration of K + ‐H 2 O pairs and strengthens the catalyst's water binding affinity, thereby enhancing water adsorption and dissociation. This work provides a feasible strategy for designing efficient non‐precious metal catalysts by manipulating the hydrogen bonding network via an IEF.