Oxygen Vacancy Engineering of Co₃ O₄ Nanocrystals through Coupling with Metal Support for Water Oxidation

Oxygen vacancies can help to capture oxygen-containing species and act as active centers for oxygen evolution reaction (OER). Unfortunately, effective methods for generating a high amount of oxygen vacancies on the surface of various nanocatalysts are rather limited. Here, we described an effective way to generate oxygen-vacancy-rich surface of transition metal oxides, exemplified with Co₃ O₄ , simply by constructing highly coupled interface of ultrafine Co₃ O₄ nanocrystals and metallic Ti. Impressively, the amounts of oxygen vacancy on the surface of Co₃ O₄ /Ti surpassed the reported values of the Co₃ O₄ modified even under highly critical conditions. The Co₃ O₄ /Ti electrode could provide a current density of 23 mA cm^-2 at an OER overpotential of 570 mV, low Tafel slope, and excellent durability in neutral medium. Because of the formation of a large amount of oxygen vacancies as the active centers for OER on the surface, the TOF value of the Co₃ O₄ @Ti electrode was optimized to be 3238 h^-1 at an OER overpotential of 570 mV, which is 380 times that of the state-of-the-art non-noble nanocatalysts in the literature.