Effect of oxygen vacancy defect introduction method on oxygen evolution performance of Co₃O₄ based electrocatalyst

Oxygen evolution (OER) on spinel Co₃O₄ induced by oxygen vacancy has been a hot research topic. Exploring the relationship between different methods of introducing oxygen vacancies, the number and spatial distribution of oxygen vacancies and electrocatalytic activity is of great significance for the design of efficient electrocatalysts. In this study, four methods of introducing oxygen vacancies, namely, air calcination, NaBH₄ reduction, H₂ reduction, and vacuum heat treatment, were used to systematically investigate the effects of introducing different amounts and spatial distributions of oxygen vacancy defects by different methods on the electrocatalytic activity of Co₃O₄. The results show that the OER electrocatalytic activity of the Co₃O₄ material with oxygen vacancies introduced by vacuum thermal treatment showed the best performance (η₁₀=257 mV), which was superior to that of NaBH₄ reduction (η₁₀=280 mV), H₂ reduction (η₁₀=286 mV) and air calcination (η₁₀=299 mV). A deep disordered structure was observed by HRTEM and XPS and ESR tests showed a decrease in the surface oxygen vacancy content, but a sharp decrease in Co³⁺, an increase in Co⁰ and an increase in the overall oxygen vacancy concentration, suggesting the creation of bulk oxygen vacancies in the deeper bulk phase of the material. This study analyzed that the oxygen vacancy generated by vacuum heat treatment has a better pre-oxidation effect on Co, and the Co (Ⅲ) is better converted to Co (Ⅳ) active substance, which is the reason for the best improvement of OER performance. This work deepens the understanding of oxygen defect catalyst and provides a new insight for the development of oxygen defect catalyst.