Activated carbon sandwiched manganese dioxide/graphene ternary composites for supercapacitor electrodes

This work presents a versatile approach for synthesis of novel ternary composites of manganese dioxide (MnO2), activated carbon (AC), and graphene and their uses as supercapacitor electrodes. The synthesis includes chemical vapor deposition of graphene on nickel foam followed by a decoration of AC on the graphene surface through a dip coating process. Hierarchical porous MnO2 top layer of the ternary composites is achieved by a self-limiting growth method via redox reactions of KMnO4 on the AC sandwich layer. Owing to the unique structure, a MnO2/AC/graphene composite electrode with 20 mM KMnO4 exhibits a highest specific capacitance of 813.0 F g(-1) at a current density of 1.0 A g(-1) and good electrochemical stability with capacitance retention of similar to 98.4% after 1000 cycles. A solid state supercapacitor based on the ternary composite electrodes possesses an energy density of 33.9 Wh kg(-1) and a power density of 319.3 W kg(-1), showing promise for energy storage applications. (c) 2018 Elsevier Ltd. All rights reserved.