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.