Enhanced charge storage by the electrocatalytic effect of anodic TiO2nanotubes

Abstract

Ordered titania nanotube (TNT) arrays were fabricated by anodization of titanium with a very fast voltage ramp speed. Co(OH)₂/TNT nanocomposite was synthesized by cathodic deposition using the as-anodized TNT as the substrate. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize the morphology, crystalline structure and chemical state. The capacitive characteristics were investigated by cyclic voltammetry (CV), charge–discharge tests, and electrochemical impedance spectroscopy (EIS). Thanks to the electrocatalytic effect of the as-anodized TNTs on the reduction of Co(OH)₂, the Co(OH)₂/TNT composite electrode exhibits a significantly enhanced charge storage capacity (an increase of 73%) when compared with Co(OH)₂/Ti (titanium as the deposition substrate). The occurrence of such an electrocatalytic effect is suggested to be related to the nano-sized TiO₂ crystals (rutile) embedded in organized amorphous TNTs. Co(OH)₂/TNT demonstrates enhanced specific energy, high rate capability and good cyclability, and can be a potential electrode of choice for supercapacitors.