Hollow Co3O4 nanoparticles immobilized rGO/Carbon monolith as an electrode material for high-performance supercapacitors

In this work, we prepared a hollow Co3O4 nanoparticles (NPs) immobilized reduced graphene oxide (rGO)/carbon monolith (HCGCM) via a one-step carbonization method. The doping of nanomaterial and transition metal oxide can improve the poor conductivity and low capacitance of pure carbonaceous materials. The optimal addition concentration of polystyrene microspheres as a template provided the HCGCM composite with a hierarchical pore structure and a large specific surface area (1600 cm2/g), which is conducive to generating sufficient electroactive sites. At the same time, three dimensional (3D) interconnected pores shorten ion transport paths and reduced diffusion resistance of ions. Due to the existence of pseudocapacitive behavior, the HCGCM composite, as an electrode material working in a three-electrode system, achieved a high capacitance value of 1106 F/g at a current density of 1 A/g. In two-electrode system, the asymmetric supercapacitor had excellent stability performance and remained about 86.7% capacitance after 5000 cycles test. Moreover, it also exhibited a maximum energy density of 66.7 Wh/kg at power density of 750 W/kg. Thus, the strategy of manufacturing 3D porous electrodes is beneficial to improve the overall electrochemical performance of supercapacitors.