Catalytic Activity of Nanometer-Sized Ir–Ox Catalysts with Different Coordination Numbers for Electrocatalytic Oxygen Evolution

High-performance single-atomic Ir catalysts can significantly reduce the cost of proton exchange membrane water electrolysis catalysts due to their ultrahigh atomic utilization. However, difficulties remain for a thorough understanding of the coordination structures and their impact on the electrocatalytic oxygen evolution (OER) catalytic activities. In this study, a series of single Ir–Ox catalysts with different coordination numbers (Ir–Ox, where x represents the O coordination number) are simulated using density functional theory calculations, and the effect of coordination number variation on the catalyst performance is investigated. The results show that the optimized electronic structure of the single Ir–O5 coordination structure significantly reduces the free energy barrier of the rate-determining step and improves the OER catalytic activity of the catalyst by promoting electron transfer and optimizing *O intermediate adsorption. Guided by these results, we successfully prepared the single Ir–O5 structure by introducing Ir into Co3O4. At a current density of 10 mA/cm2, the electrocatalyst exhibits an overpotential of 266 mV, which is 40 mV lower than that of IrO2 with an Ir–O6 coordination structure. Additionally, the catalyst demonstrates excellent stability, maintaining uninterrupted operation for 900 h at a current density of 20 mA/cm2. These findings provide a theoretical basis for the preparation of high-performance iridium oxide catalysts.