Biomass derived porous carbon supported nano-Co3O4 composite for high-performance supercapacitors

Carbon based composites derived from various biomasses have exhibited excellent application prospects in the field of supercapacitors. Herein, the Co3O4 nanoparticles supported on biomass eggfruit-derived porous carbon (EPC) was prepared via solvothermal method and subsequent calcination, in which the shells of eggfruit's kernel (SEK) were used as carbon source and cobalt phthalocyanine was employed as precursor of Co3O4. The resultant composite was denoted as Co3O4@EPC and its supercapacitive performances were checked in details. Scanning electron microscopy and transmission electron microscopy images of Co3O4@EPC show that EPC has a threedimensional porous network structure, and Co3O4 nanoparticles with an average particle size of 7 nm are uniformly dispersed on the EPC carrier. In the three-electrode system with 6 mol L-1 KOH as electrolyte, the specific capacitance of Co3O4@EPC/Ni foam electrode is 781 F g(-1) at the current density of 0.5 A g(-1), which is much higher than that of p-Co3O4 electrode (429.69 F g(-1) at 0.5 A g(-1)) or EPC (125.39 F g(-1) at 0.5 A g(-1)) electrode under the same conditions. The energy density of a two-electrode device with Co3O4@EPC/Ni foam electrode as positive electrode and EPC/Ni foam electrode as negative electrode was 32.8 Wh K g(-1) at the power density of 1333 W K g(-1). In addition, the device has good cyclic stability with a capacitance retention rate of 96.7% after 20,000 cycles. These results indicate that the excellent properties of the Co3O4@EPC make it a potential electrode material for high-performance supercapacitors.