Free-standing MnO2/nitrogen-doped graphene paper hybrids as binder-free electrode for supercapacitor applications

Sandwich-type hybrid structure consisting of etched nitrogen-doped graphene paper (ENGP) and flower-like MnO2 are fabricated through a three-step method. The ENGP were synthesized by vacuum assisted flow-filtration of the dicyandiamide (DCD) and graphene oxide (GO) aqueous solution through filter membrane, followed by a carbonization process, and then by an electrochemical etching method to improve the surface active-sites and wettability. The MnO2 nanoflowers consisting of multiple thin MnO2 nanosheets were anchored on both side of ENGP by electrodeposition techniques. The optimized hybrid electrodes exhibited a high specific capacitance of 368.3 F/g at 0.2 A/g, and excellent cycling performance of 98.4% capacitance retention over 3000 cycles.