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

MgCo 2 O 4 is a promising electrode material in electrochemical energy storage devices. In this work, the supercritical CO 2 -assisted solvothermal (SCAS) method was applied to synthesize MgCo 2 O 4 nanomaterials for the first time. The crystallite size of the MgCo 2 O 4 prepared by SCAS was significantly smaller than the one prepared by the ethanol solvothermal method, reaching 9.0 nm at a CO 2 pressure of 16 MPa. The as-prepared MgCo 2 O 4 nanospheres exhibited a special spherical structure with abundant irregular pores and a high specific surface area of 69.9 m 2 /g. X-ray photoelectron spectroscopy demonstrated that the Co 3+ /Co 2+ ratio of the MgCo 2 O 4 was increased by the SCAS method and the mechanism of synthesizing MgCo 2 O 4 nanospheres was explored. In addition, the MgCo 2 O 4 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 MgCo 2 O 4 nanoparticles with special morphology and high specific surface area, which are expected to be applied in high-performance electrode materials.