Abstract: TiO₂ nanotube (TNT) arrays present excellent light trapping and electronic conduction ability. TNT film was prepared by the anodic oxidation method using Ti slice as the substrate. The morphology and structure of the TNT film were characterized by scanning electron microscopy and X-ray diffraction, respectively. Photoelectrocatalytic (PEC) reduction of Cr(VI) was carried out using the TNT arrays as the photoanode and Ti mesh as the photocathode under acid conditions and ultraviolet light irradiation. The influencing factors such as applied voltage, NaCl concentration, citric acid concentration, and Cr(VI) initial concentration were investigated. The applied voltage facilitates the separation of electron-hole pairs, making the PEC reaction rate of Cr(VI) much higher than that of photocatalysis. The introduction of NaCl increases the electrical conductivity of solution, getting enhanced PEC reaction rate of Cr(VI) to some extent. Citric acid, behaving as the hole scavenger, can capture photogenerated holes effectively. The PEC reaction rate of Cr(VI) increases with increasing citric acid concentration in a certain range. Under the conditions of 1.5 V voltage, 1.0 mol/L NaCl, and 0.5 mmol/L citric acid, the conversion of 17.7 mg/L Cr(VI) achieved 98.6% at 60 min irradiation.

Key words: titania nanotube, chromium (VI), photoelectrocatalysis, reduction