Surface characteristics and photocatalytic properties of TiO2-In2O3 composite powders by using the sol-gel method: effects of preparation conditions

摘要

TiO2-In2O3 composites were synthesized with various Ti/In molar ratios (13.5, 27 and 54), calcination temperatures (300, 450 and 600 °C) and durations (1,2 and 4 h) by the sol-gel method. The surface properties of the prepared powders were analyzed by X-ray diffraction, UV-Vis spectrophotometry, scanning electron microscopy, transmission electron microscopy, BET surface area analysis, surface charge analysis and X-ray photoelectron spectroscopy. The C.I. Reactive Red (RR2) removal efficiency of the TiO2-In2O3 composites with or without UV irradiation was determined. Analytical results reveal that at a Ti/In molar ratio of 54 and a calcination temperature of 450 °C for 2 h, the average diameter, BET surface area, pore volume and band gap of the prepared TiO2-In2O3 composite were 57 nm, 35.7 m~2/g, 0.17 cm~3/g and 2.97 eV. The removal rate constants of RR2 in the UV/TiO2-In2O3 composite systems fit pseudo-first order kinetics. The RR2 removal efficiency of the TiO2-In2O3 composite exceeded that of TiO2 or In2O3 alone, possibly owing to its greater BET surface area, hydrophilicity and separation of photogenerated electron-hole pairs. Although inversely related to the RR2 concentration, the RR2 decolorization rate constant was directly proportional to the amount of the TiO2-In2O3 composite, according to the pseudo-first order kinetics.