Direct growth of MnO2 on highly porous nitrogen-doped carbon nanowires for asymmetric supercapacitors

In this work, we present an effective route to develop composite electrodes consisting of highly porous nitrogen-doped carbon nanowires (PNCW) and manganese dioxide (MnO2), toward supercapacitor applications. The PNCW with hierarchically porous structure, prepared from polypyrrole nanowires, is used as a supporting substrate to deposit MnO2 based on a redox reaction between carbon and KMnO4. The morphology of the deposited MnO2 can be tuned by simply changing solution pH. The as-prepared PNCW/MnO2 composites possess a porous macrostructure, which is beneficial for the transport and diffusion of ions and electrons. An aqueous asymmetric supercapacitor device has been assembled using PNCW and PNCW/MnO2 as electrodes, which presents a satisfied energy density of 23.7 Wh kg−1 at 2000 W kg−1. The experimental data prove the feasibility of using PNCW as a porous carbon substrate for the preparation of composite electrodes in the asymmetric supercapacitor.