Highly ordered MnO2 nanowire array thin films on Ti/Si substrate as an electrode for electrochemical capacitor

AAO/Ti/Si substrate was successfully synthesized by a two-step electrochemical anodization of the aluminum film on the Ti/Si substrate and then used as template to grow nanowire arrays. The ordered MnO2 nanowire arrays with about 40 nm diameters had been directly fabricated on AAO/Ti/Si substrate by direct current (DC) electrodeposition. The microstructure of the nanowire arrays was investigated by field-emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Their electrochemical characterization was performed using cyclic voltammetry in 0.5 M Na2SO4 aqueous solution. The synthesized MnO2 nanowires had amorphous nature until 400 °C. The deal capacitive behavior was obtained when the as-prepared sample was heat-treated at 200 °C. The specific capacitance of the electrode was about 254 F/g.