Manganese Oxide/Single-Walls Carbon Nanotubes Electrodeposited Films for Supercapacitors

Abstract

The manganese oxide/single-walls carbon nanotubes (SWNTs) composite films were co-deposited by the potentiodynamic method via octylphenyl polyoxyethylene ether (OP-10) mediation the growth rate of electrolysis MnO2. Octylphenyl polyoxyethylene ether (OP-10) was used to obtain SWNTs suspensions through noncovalent functionalizition. At the fixed OP-10 concentration of 0.075 mol L-1, specific capacitance (SC) of the composites raised with SWNTs concentration increased and reached a maximum at SWNT concentration of 0.75 g L-1 due to porous microstructure and good electronic conductivity of SWNTs. Moreover, appropriated OP-10 concentration benefited to not only stable SWNTs suspension but also modified MnO2 electrodeposited process for the uniform distribution of nanotubes in the composites. The microstructure and electrochemical characteristics of MnO2/SWNTs composite films were affected by the SWNTs content. The supercapacitor performances of MnO2 as the ratio of SWNTs optimized were significantly improved for the electronic and ionic transport in this film should be more balance. According to electrochemical impedance spectrum, the optimal MnO2/SWNTs composite presented low charge-transfer resistance and good frequency response. The MnO2/SWNTs composite showed the maximum SC of 421 F g-1, which was four times higher than the pure MnO2, at the current of 1 A g-1. This MnO2/SWNTs composite is a promising active material for high energy density and high power density supercapacitors.