Supercritical CO2-assisted solvothermal synthesis and characterization of MgCo2O4 nanospheres for high-performance capacitance

MgCo2O4 is a promising electrode material in electrochemical energy storage devices. In this work, the supercritical CO2-assisted solvothermal (SCAS) method was applied to synthesize MgCo2O4 nanomaterials for the first time. The crystallite size of the MgCo2O4 prepared by SCAS was significantly smaller than the one prepared by the ethanol solvothermal method, reaching 9.0 nm at a CO2 pressure of 16 MPa. The as-prepared MgCo2O4 nanospheres exhibited a special spherical structure with abundant irregular pores and a high specific surface area of 69.9 m2/g. X-ray photoelectron spectroscopy demonstrated that the Co3+/Co2+ ratio of the MgCo2O4 was increased by the SCAS method and the mechanism of synthesizing MgCo2O4 nanospheres was explored. In addition, the MgCo2O4 electrode material prepared by the SCAS method exhibited a high specific capacitance of 741 F/g at 0.1 A/g. The results confirm that the SCAS method can synthesize ultrafine MgCo2O4 nanoparticles with special morphology and high specific surface area, which are expected to be applied in high -performance electrode materials.