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

Abstract

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), N₂ 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.