Study on the photoelectrocatalytic activity of reduced TiO 2 nanotube films for removal of methyl orange

Abstract The reduced TiO 2 film on which a photoelectrocatalytic (PEC) process had occurred was created from TiO 2 nanotube film electrodes by the electrochemical reduction method. The obtained samples’ structure and morphology were characterized using UV-Vis diffuse reflectance spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, photoluminescence, and X-ray diffraction. Cyclic voltammetry, linear sweep voltammetry, electrochemical impedance spectroscopy, chronoamperometry, UV-Vis absorbance spectroscopy, and Mott–Schottky plots were employed to examine the electrochemical and photoelectrochemical activities of the prepared electrodes. The results showed that the optimal conditions of cathodic polarization were a potential of −1.4 V for 60 min. The reduced TiO 2 nanotube film electrode had better photoelectrochemical activities than pristine TiO 2 under UV light due to the higher photocurrent density (13.7 mA‧cm −2 ) at 1.5 V (vs Ag/AgCl, sat. KCl reference electrode) compared to pristine TiO 2 achieving 7.3 mA‧cm −2 , indicating more effective charge separation and transport. The degradation of methyl orange (MO) on pristine TiO 2 and reduced TiO 2 electrodes was carried out in electrocatalytic (EC) and PEC conditions. The PEC process on the reduced TiO 2 electrode had the highest MO processing efficiency (98.4%), and the EC process for MO removal on reduced TiO 2 had higher efficiency (95.1%) than the PEC process on pristine TiO 2 (89.2%).