Synthesis of anatase/brookite TiO2-Bi2WO6 multiheterojunction and its photocatalytic properties under visible-light irradiation

Anatase/brookite TiO2-Bi2WO6 multiheterojunction photocatalyst (TabB) has been synthesized via solvothermal method and its physiochemical properties compared with anatase TiO2-Bi2WO6 (TaB) and brookite TiO2-Bi2WO6 (TbB) with single-heterojunction structure. Based on X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) analyses, a heterojunction was formed between TiO2 and Bi2WO6 crystals. All of the TaB, TbB, and TabB samples consisted of free plate-like Bi2WO6 particles covered by many TiO2 nanoparticles. Compared with pure TiO2 (anatase and brookite), the absorption band edge of TabB was red-shifted and the bandgap decreased. The photocatalytic activity of the as-prepared samples under visible-light irradiation was investigated using rhodamine B (RhB), revealing photocatalytic activity in the order TabB > TaB > TbB. The heterojunction structure played a vital role in enhancing charge carrier separation and thus enhancing the photocatalytic activity. The related mechanism of the heterojunction photocatalyst is systematically discussed.