Efficient α/β-Bi2O3 composite for the sequential photodegradation of two-dyes mixture

A mixture of alpha/beta-Bi2O3 and alpha/beta-Bi2O3 powders were obtained by a simple solid state reaction-annealing route at 550 degrees C. The structure, optical properties and surface area of the commercial alpha and alpha/beta-Bi2O3 and the synthesized alpha-phase and alpha/beta-composite were well characterized by X-ray diffraction, diffuse reflectance spectra and N-2 physisorption. The annealed sample at 550 degrees C showed 20% of beta-phase, forming a heterojunction of alpha/beta-Bi2O3 whereas annealing at elevated temperature (650 degrees C) lead to the alpha-phase. Optical properties showed that the presence of the beta-phase is mainly responsible for narrowing the energy band gap. The photocatalytic activity of the commercial alpha and alpha/beta-Bi2O3 and the synthesized a phase and alpha/beta-composite were investigated in degradation of single dyes, Indigo Carmine (IC) and Rhodamine-B (RhB) under both UV and visible light-induced photocatalysis. For the best photocatalyst, the photodegradation in a two-dye mixture solution was systematically studied considering the type of dye, the adsorption capacity of the samples and the behavior of dye photodegradation. The photo catalytic performance of alpha/beta-Bi2O3 was comparatively much higher than the commercial alpha and alpha/beta-Bi2O3, indicating that better performance of efficient charge separation and transfer across alpha/beta-Bi2O3 composite was obtained. Possible mechanism of the single dye and two-dye mixture degradation was given by using alpha/beta-Bi2O3 composite. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.