Facile synthesis and electrochemical properties of MnO2/carbon nanotubes

The poor electrical conductivity of MnO2 limits its use as an electrode material. To overcome this limitation, we report an easy and rapid approach to deposit nanosized MnO2 onto multi-wall carbon nanotubes functionalized with hydroxyl groups (MWCNTs-OH) by chemical reduction of KMnO4 with MnSO4 in aqueous solution under ambient conditions. Characterization with XRD and TEM reveals that the obtained MnO2/MWCNTs-OH composite is nanocrystalline and partially covered by MnO2 nanosheets with a thickness of 1-3 nm at a MnO2 loading of 20 wt%. Cyclic voltammetry (CV) and galvanostatic charge-discharge measurements reveal that the MnO2/MWCNTs-OH composite with a MnO2 loading of 20 wt% has a relatively high specific capacitance of 234 F/g at a scan rate of 2 mV/s and exhibits good cycling stability. Furthermore, the oxygen reduction reaction (ORR) shows that MnO2/MWCNTs-OH composite may have potential applications as a non-noble metal electrocatalyst in fuel cells and metal-air batteries. (C) 2013 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved