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

• Perchlorate can be reduced using Ag nanoparticles loaded TiO2 nanotube arrays.
• The photoelectrocatalytic properties of Ag-TNTs were studied upon UV irradiation.
• Influencing factors and reaction mechanisms of perchlorate reduction were discussed.

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.