Annealing effects on the compact titania nanotube arrays: Evolution of microstructure and enhanced photoelectric response

Well-aligned titania nanotube arrays (TNAs) fabricated by electrochemical anodization at high voltage of 120 V have shown superior photoelectric properties than those with similar morphology prepared by traditional anodic conditions at low voltage of 60 V. Firmly-structured TNAs with initial oxide layer can be obtained under 120 V for a growth time as short as 40 s. Effects of annealing on the TNAs structure, optical property, and photoelectric property are systematically investigated at different temperatures. It is found that the microstructures, such as crystallinity, grain size, and phase composition, can be optimized by calcination at moderate temperature around 600 °C, under which the desired optical absorption and the optima photoelectric quantum yield are also observed respectively from diffusion reflection spectroscopy and transient photoelectric response analysis. The extreme fast and economic route for synthesizing firmly-structured TNAs at high voltage is promising for exploring 3D electrodes with an optimized structure and enhanced photo-electrochemical performance.