Study on the structure and supercapacitive properties of Mesoporous Co3O4 nanosheets

Measurements of XRD (X-ray diffraction), TEM (transmission electron microscopy) and N2 adsorption-desorption isotherms were combined to study the phase and microstructure of mesoporous Co3O4 nanosheets synthesized at different temperatures. The mechanism of calcination temperature influencing the supercapacitive performance of the Co3O4 nanosheets was also investigated. It is indicated from the XRD and TEM results that the as-prepared Co3O4 nanosheets are in a pure spinel phase and in a mesoporous morphology, and the crystallinity increases with the calcination temperature. The N2 adsorption-desorption isotherms measurement shows a decrease of the specific surface area from 279 to 22 m2/g as the calcination temperature increases from 300 to 500 ℃. Electrochemical characterization reveals the best supercapacitor performance of the nanosheets obtained at 400 ℃, with a capacity of 151 F/g that is twice the values of the products calcined at 300 and 500 ℃. Based on these results, it was proposed that the synergistic effects of the crystallinity and the surface microstructure of the mesoporous microstructures are key factors for the supercapacitive performance of the Co3O4 nanosheets. Compared with the nanosheets calcined at 300 ℃, the 400 ℃ sample possesses better crystallinity, which is beneficial to the electron transfer during the redox reaction of the electrodes. In comparison with the nanosheets calcined at 500 ℃, the 400 ℃ calcined sheets have the proper BET specific surface area, facilitating the participation of electrolyte in the electrode reaction.