Electrochemical Formation Mechanism for the Controlled Synthesis of Heterogeneous MnO2/Poly(3,4-ethylenedioxythiophene) Nanowires

Abstract

The formation mechanism of a coaxial manganese oxide/poly(3,4-ethylenedioxythiophene) (MnO(2)/PEDOT) nanowire is elucidated herein by performing electrodeposition of MnO(2) and PEDOT on Au-sputtered nanoelectrodes with different shapes (ring and flat-top, respectively) within the 200 nm diameter pores of an anodized aluminum oxide (AAO) template. It is found that PEDOT prefers to grow on the sharp edge of the ring-shaped electrode, while MnO(2) is more likely to deposit on the flat-top electrode due to its smooth surface. The formation of coaxial nanowires is shown to be a result of simultaneous growth of core MnO(2) and shell PEDOT by an analysis of the current density resulting from electrochemical deposition. Furthermore, the structures of the MnO(2)/PEDOT coaxial nanowires were studied for their application as supercapacitors by modifying their coelectrodeposition potential. A potential of 0.70 V is found to be the most favorable condition for synthesis of MnO(2)/PEDOT coaxial nanowires, resulting in a high specific capacitance of 270 F/g. Additionally, other heterogeneous MnO(2)/PEDOT nanostructures are produced, such as nanowires consisting of MnO(2) nanodomes with PEDOT crowns as well as segmented MnO(2)/PEDOT nanowires. This is accomplished by simply adjusting the parameters of the electrochemical deposition. Finally, in smaller diameter (50 nm) AAO channels, MnO(2) and PEDOT are found to be partially assembled into coaxial nanowires due to the alternative depletion of Mn(II) ions and EDOT monomers in the smaller diameter pores.