Oxygen-deficient Co3O4 submicron porous sphere films as highly active supsercapacitor electrodes

Herein, we report Co3O4 films with different content of oxygen vacancies and shapes of particles for supercapacitor electrodes. Under the similar area ratio of OH peak in the XPS spectrum of oxygen elements, the specific capacitance of electrode films with hollow spongy-like particles (963 F/g under a scan rate of 5 mV/s) is 1.6 times higher than that of the electrodes with solid irregular particles (596 F/g), indicating the effect of particle shapes on electrochemical properties. The films composed of submicron porous spheres and containing highest content of oxygen vacancies exhibited the specific capacitances as high as 1700 F/g under the scan rate of 5 mV/ s. By contrast, after post heating treatment, the specific capacitance as 994 F/g was left due to losing of oxygen vacancies. Additionally, the first-principles calculations demonstrate that oxygen vacancies facilitate reaction between hydroxyl and Co3O4 and improve electronic conductivity. Meanwhile, 96.9% of the initial capacitance was maintained after consecutive 13,000 cycles at a scan rate of 20 mV/s. All in all, this work not only provides insight on the effects of characters of metal oxide electrodes on electrochemical properties, but also supplies a new route for preparation of oxygen-deficient metal oxide electrodes with desired nanostructures.