Oxygen Vacancy Concentration Effect on Co₃O₄ for High-Quality Energy Storage

Introducing oxygen vacancies is regarded as effective in enhancing the inherent electrical conductivity of metal oxides. However, an effective guideline regarding various vacancy concentration effects on electrochemical properties is lacking. Herein, density functional theory (DFT) is initially employed to predict the influence of vacancy concentration on Co3O4. Results demonstrate that an improved vacancy content substantially enhances the OH– adsorption and charge–discharge reaction kinetics. Guided by DFT calculations, Co3O4 nanomaterials with different vacancy concentrations are successfully designed by using a facile strategy. Electrochemical test results show that the involved electrical conductivity and redox reaction kinetics gradually enhance with increasing number of oxygen vacancies; these findings align with the theoretical calculation results. The optimal Co3O4 electrode rich in oxygen vacancies (H-Co3O4) has a high specific capacitance of 1168.1 F g–1 at 1 A g–1, along with remarkable cycling stability, retaining 128% of its capacitance after 30,000 cycles. Furthermore, an asymmetric supercapacitor utilizing H-Co3O4 as the positive electrode exhibits an outstanding energy density of 37.4 W h kg–1 at a power density of 750 W kg–1 and maintains 79.3% of its capacitance after 10,000 cycles.