One-step molten-salt method fabricated Bi2Ti2O7/Bi4Ti3O12 composites with enhanced photocatalytic activity

In this work, Bi2Ti2O7/Bi4Ti3O12 composite photocatalysts composed of Bi2Ti2O7 sub-micron-sized particles and Bi4Ti3O12 nanosheets with exposed {001} facets, were synthesized by a one-step molten salt method. The contents of Bi2Ti2O7 in the Bi2Ti2O7/Bi4Ti3O12 composites were adjusted by the Bi/Ti molar ratio of raw materials. The structure, morphology and optical absorption properties were characterized by XRD, SEM, TEM, HRTEM and UV–Vis diffuse reflectance. Compared with pure Bi4Ti3O12, the as-prepared Bi2Ti2O7/Bi4Ti3O12 composite (for the Bi/Ti ratio ~4:3.2) exhibit more excellent photocatalytic activities in the degradation of methyl orange (MO), Rhodamine B (RhB) and mixed dyes (RhB and MO) in aqueous solutions under simulated solar light irradiation. Furthermore, for the mixed dye solution, the as-prepared composite photocatalysts show preferential decomposition of MO in comparison to RhB. To detect the reactive species, the scavenger tests for the composite photocatalysts were carried out and the results indicate that the photogenerated h + would play an important role in the degradation of RhB and MO dyes. Based on the experimental results in this work, the possible photocatalytic degradation mechanism of Bi2Ti2O7/Bi4Ti3O12 composites was also discussed.