Facile synthesis and electrochemical properties of MnO2/carbon nanotubes

► A facile route to synthesize MnO2/MWCNTs was devised in aqueous solution under ambient conditions. ► Composite of MWCNTs loaded with 20 wt% MnO2 nanosheets has a high specific capacitance of 234 F/g. ► 80% of the initial capacitance of the MnO2/MWCNTs (20 wt%) is maintained after 1000 charge-discharge cycles.