Abstract: The application of non-precious metal catalysts in alkaline oxygen reduction reactions (ORR) has become a focal point in the field of new energy research. Among these, transition metal oxides, particularly spinel oxides, have garnered significant attention due to their multivalent electronic structures and exceptional electrocatalytic properties. Despite numerous reports on such materials, the mechanistic roles and performance differences of the two active sites in their typical dual-site structures remain unclear. This study focuses on spinel Co₃O₄ as a base material and introduces reaction-inert Zn²⁺ and Al³⁺ to occupy specific sites, successfully synthesizing spinel oxides ZnCo2O4 and CoAl2O4 that exclusively expose Co3+ and Co2+ active sites. Electrochemical testing in half-cell configurations revealed that the half-wave potential of Co3O4 is 50 mV higher than that of ZnCo2O4, while the half-wave potential of ZnCo2O4 significantly exceeds that of CoAl2O4 by 120 mV. This demonstrates that the Co3+ located at the octahedral sites is the primary active site for the ORR. Similarly, in zinc-air battery tests, Co3O4 exhibited the highest peak power density, followed by ZnCo2O4, with CoAl2O4 showing the lowest performance, consistent with the electrochemical behavior observed in half-cell tests. In situ infrared spectroscopy analysis further revealed that ZnCo2O4 exhibits additional adsorption peaks for *O2- and O2 compared to CoAl2O4, indicating that the Co3+ at the octahedral sites has a stronger adsorption capacity for *O2- and O2 than the Co2+ at the tetrahedral sites, thereby enhancing the ORR activity. This study elucidates the performance difference mechanisms of various active sites in spinel oxides during ORR, providing a theoretical foundation for designing efficient spinel oxide catalysts.

Key words: Zinc-air battery; Oxygen reduction reaction, Non-precious metal catalyst, Spinel oxide, In situ electrochemical infrared spectroscopy