Co3O4 Anchored on Meshy Biomass Carbon Derived from Kelp for High‐Performance Ultracapacitor Electrode

Abstract In this paper kelp was used as the carbon precursor to prepare a biomass carbon with meshy microstructure, and Co3O4 nanoparticles were further modified on the meshy biomass carbon (MBC) by using solvothermal and pyrolysis methods. The prepared Co3O4@MBC composite combined the special structure of MBC with uniformly distributed Co3O4 nanoparticles, which provided large specific surface and good conductivity. Different methods including scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and nitrogen adsorption-desorption were used to characterize the structure and performances of composite. Co3O4@MBC composite was used to construct an electrode for supercapacitor, which had better electrochemical performance than that of pristine Co3O4 nanoparticles and MBC electrodes. The highest specific capacitance (1212.4 F·g-1 at 0.5 A·g-1) could be obtained with excellent cycle stability and the capacity retention was 99.5% at 2 A·g-1 after 2000 cycles, which could be attributed to synergistic effects of both pseudocapacitance and electric double layer capacitance under optimized carbon-cobalt ratio. Furthermore, an asymmetric supercapacitor system was constructed utilizing Co3O4@MBC as positive electrode with MBC as negative electrode. This two-electrode system provided a good performance with energy density of 59.82 Wh·kg-1 at a power density of 700 W·kg-1, highlighting the potential application in efficient energy storage device.