Efficient OER catalysis on Ir-doped Co₃O₄: Understanding Double and Quadruple Oxygen Coupling Mechanisms on Bimetallic sites

Constructing electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing renewable energy systems. In this study, the OER performances of Ir-doped Co₃O₄ with (100), (110), and (311) surfaces using first-principles calculations. Of particular focus is on the oxidative coupling mechanism (*OO*, *OOOO*) at bi-nuclear sites (Co-Co, Ir-Co, and Ir-Ir). For double oxygen coupling mechanism (DOCM), it is found that Ir-Co sites exhibite the best OER performance than other sites. This result is an attribute of change the geometry and electronic configuration of the catalyst surface by the introduction of Ir atoms. In the case of Ir-Ir sites, the strong Ir-O bond cause difficulty in oxygen desorption, resulting in a high energy barrier and overpotential. Thus, the dual-IrO structure of the DOCM is regarded as the initial state for the quadruple oxygen coupling mechanism (QOCM) in the next four electrons/protons translation process. For QOCM, the result showed that Ir-Co/Ir-Ir sites displayed excellent OER performance than Co-Co sites. This finding implies that both DOCM and QOCM could occur in OER on Ir-doped Co₃O₄ with low overpotential. These results increased our understanding of the mechanism of OER process on doping catalysis with bimetallic synergic effect.