Sol–gel template synthesis of highly ordered MnO 2 nanowire arrays

Abstract

In this paper, anodic aluminum oxide (AAO) templates with uniform pore diameter and periodicity were fabricated using a two-step oxidizating method at a constant current of 1.5 A dm −2 in a mixed solution of 0.5 M sulfate acid and 5 g L −1 oxalic acid at room temperature, pore-widening was done in 5 wt.% phosphoric acid. Then, arrays of manganese dioxide nanowires were prepared by combining the AAO template and a sol–gel solution containing Mn(CH 3COO) 2 and citric acid. SEM was used to characterize the structure of AAO and MnO 2 nanowires. The results show that uniform length and diameter of MnO 2 nanowires were obtained, and the length and diameter of MnO 2 nanowires are dependent on the pore diameter and the thickness of the applied AAO template. The pore diameter of the AAO was about 70 nm, the diameter of the MnO 2 nanowires was 70 nm and the length of the MnO 2 nanowires was about 500–700 nm. XRD analysis indicate the MnO 2 nanowires was α-MnO 2 polymorph. The results of cyclic voltammetry indicated that the α-MnO 2 nanowires are promising electrode materials for application in supercapacitors, the specific capacity of the electrode was 165 F g −1.