Facile synthesis of reduced graphene oxide@Co3O4 composites derived from assisted liquid-phase plasma electrolysis for high-performance hybrid supercapacitors

Reduced graphene oxide@Co3O4 (rGO@Co3O4) composites are widely developed as promising electrode ma-terials; however, their practical applications are restricted owing to their complex synthesis process. In the current work, we developed a rapid, efficient, and facile method for the one-step synthesis of rGO@Co3O4 composites via assisted liquid-phase plasma electrolysis. During the plasma electrolysis process, uniform and ultrafine Co3O4 particles are grown in-situ on rGO. The rGO@Co3O4 composites present a specific capacitance as high as 1249.0F/g at 1 A/g and a capacitance retention of 89.7 % over 10,000 cycles in a three-electrode system. The superior electrochemical performance is ascribed to the synergistic effect of the high specific capacitance Co3O4 and highly conductive rGO, which is conducive to promoting the transportation efficiency of ions/elec-trons and reducing the volume change of Co3O4 in the charge-discharge cycle. Asymmetric supercapacitors are also assembled using rGO@Co3O4 composites as the positive electrode and rGO as the negative electrode. The asymmetric supercapacitors achieve a specific capacitance of 72.3F/g at 1 A/g, display an energy density of 23.6 Wh/kg at a power density of 0.4 kW/kg, and exhibit superior cycle stability with a capacitance retention of 88.2 % over 10,000 cycles at 5 A/g. The current work provides a rapid, efficient, and facile method for the one-step synthesis of rGO-transition metal oxide electrodes as advanced energy storage devices.