Microstructural, optical, and photocatalytic properties of TiO2–Bi2O3–GO thin films obtained by sol-gel for applications with sunlight

Abstract

The following study presents the structural, optical, and photocatalytic properties of thin films of titanium dioxide (TiO₂) and bismuth trioxide (Bi₂O₃) in their pure state, as well as mixtures of both oxides in different atomic proportions (with respect to Ti and Bi) and as films modified with a dispersed phase of graphene oxide (GO). The films were sintered at 400 °C, 450 °C, 500 °C and 550 °C. The synthesis of the oxides was carried out by the sol-gel method and the material deposits were synthesized by the dip-coating technique. For mixtures with atomic proportions of 50% and 70% Bi₂O₃, bismuth titanates were obtained with Bi₂(Ti₂O₇) (cubic) stoichiometry at 550 °C and Bi₄Ti₃O₇ (orthorhombic) stoichiometry at 500 °C, respectively. It was determined that the Bi₂(Ti₂O₇) compound presents the best photocatalytic properties in the degradation of tartrazine in aqueous solution using solar radiation, achieving up to 30% in the photodegradation of the dye. The GO was incorporated in 2% p/p to the precursor solutions of TiO₂ and Bi₂O₃; the resulting materials presented a better photocatalytic activity.