BiVO4 Microspheres Coated with Nanometer-Thick Porous TiO2 Shells for Photocatalytic Water Treatment under Visible-Light Irradiation

Herein, we designed and synthesized well-defined BiVO4@porous TiO2 shell microspheres, with different core diameters by a facile hydrothermal method, for efficient visible-light-driven photocatalysis. The developed complex particles contained single solid BiVO4 cores and nanometer-thick porous TiO2 shells, composed of many nanosheets, and showed high stability and excellent photocatalytic activity for degrading both organic dyes and colorless organic contaminants under visible-light irradiation, much better than the benchmark of commercial P25 and bare BiVO4 microspheres of the same size. Compared to the bare BiVO4 microspheres, the BiVO4@TiO2 heterostructures showed improved photocatalytic activity, which was ascribed to (i) the formed BiVO4/TiO2 heterojunction with a defect energy level generated by the Ti3+ ions during the nanoporous TiO2 shell formation, which greatly promoted the charge carrier seperation and transfer between the BiVO4 and TiO2 during the photocatalysis process; (ii) the unique core@porous-shell structure that led to the intimate contact between the BiVO4 core and the TiO2 shell, facilitating the interfacial charge transfer; and also more importantly, (iii) the unique nanostructured porous TiO2 shell composed of numerous tiny TiO2 nanosheets that provided a large surface area for the easy adsorption of organic molecules and made the separated charge carriers directly available to the reactants, largely suppressing the charge carrier recombination and further increasing the photocatalytic efficiency. This study provides a feasible approach for the rational design of high-efficiency core@ porous-shell nanostructured photocatalysts for photocatalytic water and wastewater treatment under visible-light irradiation.