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

Abstract This work presents a versatile approach for synthesis of novel ternary composites of manganese dioxide (MnO 2 ), 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 MnO 2 top layer of the ternary composites is achieved by a self-limiting growth method via redox reactions of KMnO 4 on the AC sandwich layer. Owing to the unique structure, a MnO 2 /AC/graphene composite electrode with 20 mM KMnO 4 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 ∼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.