Facile strategy for preparing the composite of MoS2 microspheres and N/S dual-doped graphene stabilized by graphene quantum dots for all-solid-state asymmetric supercapacitor

Abstract

The composite (GQDs-MoS2/NSG) of molybdenum disulfide (MoS2) and N/S dual-doped graphene (NSG) has been successfully synthesized through in situ self-assembly by a new hydrothermal strategy using graphene quantum dots (GQDs) as auxiliary agent. The effect of GQDs dosage on the morphology of MoS2 has been investigated. Results show that adding GQDs to the nanohybrids can significantly improve the dispersion uniformity and binding state of MoS2 and NSG, and increase the overall defect density. When the GQDs dosage is 20 mg, the sample GQDs-MoS2/NSG20 has the best performance, and its specific capacitance reaches 564.3 .Fg−1 at a scan rate of 10 .mV s−1. Under a large current density of 20 .A g−1, the specific capacitance retention rate of GQDs-MoS2/NSG20 is 92.8% after 10,000 constant current charge/discharge loops. The contribution of the pseudocapacitance of GQDs-MoS2/NSG20 at 10–200 mV.s−1 was studied by using dynamic analysis and density functional theory calculation. All-solid-state asymmetric supercapacitor (ASC) was fabricated with NSG and GQDs-MoS2/NSG20. When the power density is 900 W.kg−1, the energy density reaches 68.8 Wh.kg−1. At a current density of 20 A.g−1, the specific capacitance retention rate is 92.2% after 10000 constant current charge/discharge loops.