Enhancement of Supercapacitor Performance of Carbon Nanocages by Surface Functionalization

Oxygen-containing functional groups can be introduced on the surface of carbon nanocages (CNCs) without damaging the skeleton structure. The functionalized CNCs were used as the electrode materials for supercapacitor. The specific capacitance of CNC-6M reached 255 F.g(-1) and increased 34% as compared to 188 F.g(-1) of pristine CNC at a current density of 1 A.g(-1). At the same current density, the specific capacitance of the as-functionalized CNCs was significantly higher than that of pristine CNCs, namely, the surface functionalization for CNCs could obviously enhance the supercapacitors performance. Furthermore, at a high current density of 100 A.g(-1), the specific capacitance of as-oxidized CNCs still retained at a level of 111 similar to 167 F.e(-1) i.e., they exhibited good resistance to high current charge and discharge. After 10 000 charging- discharging cycles at a current density of 10 A.g(-1), the specific capacitance of CNC-6M only dropped from 196 to 176 F.g(-1), i.e., the functionalized CNCs possessed good cycle stability. The excellent supercapacitor performance of the as-functionalized CNCs is ascribed to the hierarchical pore structure, high surface area, good electrical conductivity of CNCs as well as the improved wettability and pseudocapacitance derived from the oxygen-containing functional groups.