MnO2-decorated hierarchical porous carbon composites for high-performance asymmetric supercapacitors

In this study, the growth of 1-dimensional manganese oxide (δ-MnO2) nanowire on hierarchical ordered mesoporous carbons/graphene composites (C) was synthesized by a relatively low-cost, simple, effective and eco-friendly redox process. It is found in both experimental results and theoretical simulations that the carbon surface, especially the mesoporous channels of ordered mesoporous carbons (amorphous carbons), would be favorable to serve as the nucleated sites for the growth of MnO2 nanowires. Likewise, the strong adsorptive interactions between MnO2 and amorphous carbons result in the high deposition efficiency of MnO2 on C (98%) and the outstanding stability of MnO2-decorated hierarchical porous carbon composites (MnO2@C) together with the relatively low equivalent series resistance. This electrode material exhibits excellent electrochemical behavior with a specific capacitance high up to 756.2 F g−1 in KOH electrolytes. In addition, an asymmetric supercapacitor (ASCs) assembled by using MnO2@C and C as the positive and negative electrodes in 1.0 M Na2SO4 solution achieves a maximum energy density of 34.56 Wh kg−1 at a power density of 450 Wkg-1 and excellent cycling stability. The results demonstrate the MnO2-decorated hierarchical porous carbon composites are promising candidates for the future high-performance supercapacitors.