Self-assembled 3D architectures of Bi2TiO4F2 as a new durable visible-light photocatalyst

A new hierarchical visible-light-driven photocatalyst Bi2TiO4F2 was synthesized by a solvothermal method for the first time. The photocatalyst was characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), N-2 adsorption-desorption (BET), UV-vis diffuse reflectance spectroscopy (DRS). Such hierarchical Bi2TiO4F2 microspheres assembled by nanosheets were fabricated via an Ostwald ripening process in the absence of soft templates (surfactants). The as-prepared samples' bimodal pore-size distributions in the mesoporous region consisted of smaller intra-aggregated pores with peak pore diameter of ca. 4.6 nm and larger inter-aggregated pores with peak pore diameter of ca. 17.0 nm. The band gap of the obtained Bi2TiO4F2 was estimated to be about 2.71-3.06 eV for various solvothermal treatment time. Owing to the hierarchical structure with bimodal pores, low band gaps and high crystallinity, the Bi2TiO4F2 microspheres exhibited high photocatalytic performance and durability for the degradation of rhodamine B (RhB) under visible light (> 420 nm). It was proved that the photo-generated holes and OH radicals played an essential role for the oxidation of RhB.