Three-dimensional sulfur-doped graphene supported cobalt-molybdenum bimetallic sulfides nanocrystal with highly interfacial storage capability for supercapacitor electrodes

Abstract

In order to obtain electrode materials for supercapacitors with a high specific capacitance, excellent stability and eco-friendly nature, cobalt-molybdenum bimetallic sulfides nanocrystal is designed on high-surface-area three-dimensional sulfur-doped graphene (CoMo2S4/3DSG) via annealing incorporation with hydrothermal method in this paper. We thoroughly investigate the electrochemical properties of CoMo2S4/3DSG composites as electrode materials in KOH and Na2SO4 electrolytes, respectively. The as-prepared hybrids display a higher specific capacitance of 1288.33 F g−1 in the KOH electrolyte than in the Na2SO4 electrolyte (991.67 F g−1) at a current density of 1 A g−1. It maintains more than 90% of its initial specific capacitance in both electrolytes after 2000 cycles. In addition, the asymmetric supercapacitor assembled with CoMo2S4/3DSG (positive electrode) and 3DSG (negative electrode) electrodes show outstanding performance. In the KOH electrolyte, the capacitor CoMo2S4/3DSG//3DSG has a maximum energy density of 38.73 Wh kg−1 at a power density of 0.81 kW kg−1 whilst it exhibit an energy density as high as 47.32 Wh kg−1 at a power density of 0.94 kW kg−1 in the Na2SO4 electrolyte. This confirms that CoMo2S4/3DSG composites have high capacitance and excellent capacity retention in both KOH and Na2SO4 electrolytes.