Photoelectrocatalytic reduction of perchlorate in aqueous solutions over Ag doped TiO₂ nanotube arrays

Photoelectrocatalytic reduction of aqueous perchlorate using Ag nanoparticles loaded TiO₂ nanotube arrays (Ag-TNTs) in the presence of a hole scavenger (citric acid, Cit) under UV light irradiation was investigated in this study. TiO₂ nanotube arrays (TNTs) were prepared by anodic oxidation and Ag nanoparticles were loaded on TNTs by photodeposition. Ag-TNTs were characterized by X-ray diffraction, scanning electron microscope and X-ray photoelectron spectroscopy. The influences of Ag doping content, photogenerated electron, photogenerated hole, hydroxyl radical, initial pH and applied voltages on photoelectrocatalytic perchlorate reduction were studied and the optimum reaction conditions were determined. Results indicated that Ag-TNTs have the best photoelectrocatalytic activity when the nominal mass ratio of Ag to TiO₂ is 0.84%. With an initial perchlorate concentration of 0.001 mM, the perchlorate reduction efficiency can reach 62% in the presence of Cit (0.15 mM) after 6 h reaction (368 ± 0.5 K) at applied voltage of 1.5 V.