Low Temperature Heat Treatment of Anodic TiO2 Nanotube Array Thin Film and Their Photo-Electrochemical Properties

Highly ordered TiO2 nanotube arrays have been fabricated via anodization in NH4HF2/glycol electrolyte at 30 V for 2 h. The obtained TiO2 nanotube array is amorphous and can be transferred into anatase by hydrothermal or solvothermal annealing. The NaCl aqueous solution and ethanol was respectively used as reaction solution during the hydrothermal or solvothermal process. It's open circuit potential (OCP) in 3.5% NaCl aqueous electrolyte decreased under the metal halogen light irritation and increased after the light was cut off. The biggest value of the decrease is about 0.45 eV, which means that such kind of thin films can be used as photo-induced cathodic protection for metals.