Oxidation-Etching Preparation of MnO2Tubular Nanostructures for High-Performance Supercapacitors

1D hierarchical tubular MnO2nanostructures have been prepared through a facile hydrothermal method using carbon nanofibres (CNFs) as sacrificial template. The morphology of MnO2nanostructures can be adjusted by changing the reaction time or annealing process. Polycrystalline MnO2nanotubes are formed with a short reaction time (e.g., 10 min) while hierarchical tubular MnO2nanostructures composed of assembled nanosheets are obtained at longer reaction times (>45 min). The polycrystalline MnO2nanotubes can be further converted to porous nanobelts and sponge-like nanowires by annealing in air. Among all the types of MnO2nanostructures prepared, tubular MnO2nanostructures composed of assembled nanosheets show optimized charge storage performance when tested as supercapacitor electrodes, for example, delivering an power density of 13.33 kW·kg–1and a energy density of 21.1 Wh·kg–1with a long cycling life over 3000 cycles, which is mainly related to their features of large specific surface area and optimized charge transfer pathway.