Enhanced photoelectrocatalytic performance of SnO2/TiO2 rutile composite films

Ordered rutile TiO2 nanorods grown on transparent electro-conductive F-doped SnO2-coated (FTO) glass substrates were prepared by a simple hydrothermal method using tetrabutyl titanate as the precursor and then calcined at various temperatures. The prepared SnO2/TiO2 composite film samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The photoelectrocatalytic (PEC) activity was evaluated by PEC degradation of methylene blue (MB) aqueous solutions under UV-LED light irradiation. The results showed that rutile TiO2 nanorods with diameters of ca. 300–700 nm and lengths of ca. 5 μm vertically grew on the FTO substrate. The resulting rutile TiO2 arrays exhibited excellent stability upon annealing in a temperature range of 300–500 °C. The sample calcined at 400 °C exhibited the highest PEC activity due to the combined effects of several factors including its one-dimensional morphology, high crystallinity, close contact between the TiO2 nanorods and SnO2 layers, SnO2/TiO2 n–n heterojunction and the applied external electrostatic field. The proposed enhanced PEC mechanism was further confirmed by the transient photocurrent response and electrochemical impedance spectroscopy (EIS) experiments.