Fabrication of high-performance symmetric pseudocapacitor by synthesizing ionic liquid-modified graphene/MoS2 NS binary electrode

Abstract

The combination of graphene with metal sulfides has always been getting attention from researchers due to the compatibility in their two-dimensional structure with active sites on their edges and their exceptional optical, magnetic, and physiochemical properties. Herein, we synthesize highly efficient pseudocapacitive electrode material using ionic liquid-modified graphene (IL-rGO) and ultrathin MoS2 nanosheets (MoS2 NS). The electrochemical properties of graphene were tuned by modifying its surface with green solvents such as ionic liquids. Modification of the graphene surface with IL increased the number of active sites at the edges, and provided a more compact arrangement to the graphene layers which enabled them to accommodate MoS2 NSs between them. Among the synthesized binary electrodes, 1.5 g IL-modified rGO loaded with 15 wt% of MoS2 NS electrode, the PIRM15 binary electrode, exhibits a high specific capacitance of 955 F/g. TEM micrographs of the PIRM15 electrode delineated the intercalation of MoS2 NSs between the graphene layers. The PIRM15 electrode displayed 93.7 % of pseudocapacitance and 6.7 % electrical double-layer capacitance. The symmetric pseudocapacitor integrated with the PIRM15 binary electrode possesses 97 % capacitance retention and 87 % coulombic efficiency at 0.008 A. The pseudocapacitor's calculated energy and power densities are 25 Wh/kg and 3333 W/kg at a current of 0.003 A and 0.05 A, respectively.