Synthesis of tin and molybdenum co-doped TiO2 nanotube arrays for the photoelectrocatalytic oxidation of phenol in aqueous solution

Tin and molybdenum co-doped titanium dioxide nanotube arrays was prepared by single-step anodization of titanium plate (Sn-Mo-TiO2 NTs/Ti electrode). The Sn-Mo-TiO2 NTs/Ti electrode was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The length and inner diameter of nanotubes increased with the increase of anodization voltage. The influences of factors, such as anodization voltage, anodization time, concentrations of Sn4+ and Mo6+, and calcination temperature, on the preparation of the electrode were studied by chronoamperometry under simulated sunlight irradiation. The optical performance of Sn-Mo-TiO2 NTs/Ti electrode was tested by UV-vis spectrophotometer. Sn-Mo-TiO2 NTs/Ti electrode exhibited high adsorption in the visible region relative to pure titanium dioxide nanotube arrays. Additionally, the chronoamperometry test results highlighted that the doping of tin and molybdenum could enhance the photoelectrochemical performance of the electrode. The electrode exhibited good photoelectrocatalytic oxidation capacity on phenol at 0.5 V constant bias voltage. Applied bias voltage enhanced the photocatalytic efficiency of nanotube arrays via promoting the separation of photo-generated electron-hole pairs. A possible degradation process for phenol was proposed.