Sol-gel prepared InTaO₄ and its photocatalytic characteristics

InTaO₄ is an efficient visible-light photocatalyst, which used to be synthesized by solid-state fusion at over 1100 °C. However, irregular morphology and severe agglomeration of particles were acquired due to nonuniform fusion of solid precursors. In this study, InTaO₄ was synthesized by two sol-gel routes, the thermal hydrolysis and esterification methods. The precursors were indium (III) nitrate pentahydrate [In(NO₃)₃] and tantalum(V) butoxide [Ta(OC₄H₉)₅] dissolved in solutions. The InTaO₄ powders with a uniform grain size of 17.7 nm were successfully synthesized using the esterification method at a calcination temperature of 950 °C. A uniform InTaO₄ thin film nearly 40 nm thick formed on an optical fiber at 1100 °C using the sol prepared by the esterification method. For the first time, InTaO₄ was evaluated by the photocatalytic activity of CO₂ photo reduction, which was conducted in aqueous solution under visible light irradiation. Cocatalyst NiO was loaded on the surface of InTaO₄ to further enhance the methanol yield. The methanol yields of NiO/InTaO₄ by esterification method were significantly higher than those by solid-state fusion. The esterification method provided homogeneous mixing of Ta(OC₄H₉)₅ and In(NO₃)₃, resulting in nano-sized InTaO₄ with uniform crystallinity and superior photocatalytic activity.