Colloidal Synthesis of Ultrathin Monoclinic BiVO4 Nanosheets for Z-Scheme Overall Water Splitting under Visible Light

Recently, ultrathin 2D photocatalysts have attracted people's attention due to their performances in the area of solar energy conversion. However, the synthesis of ultrathin 2D photocatalysts with a nonlayered crystal structure is still full of challenges. Herein, ultrathin 2D BiVO4 nanosheets (NSs) with monoclinic crystal structure are synthesized through a convenient colloidal two-phase method. The as-prepared BiVO4 NSs possess a thickness of less than 3 nm but a diameter larger than 1.2 mu m. Furthermore, the presence of HNO3 facilitates the growth of BiVO4 NSs with nearly naked surfaces, largely exposed {010} planes, and widely distributed oxygen vacancies (V-O) inside the crystalline structure, which are of great benefit to their photocatalytic activity under visible light irradiation. As a result, our ultrathin 2D BiVO4 NSs exhibit an impressive photocatalytic performance for water oxidation. The O-2 evolution rate is 107.4 mu mol h(-1), and the apparent quantum yield (AQY) is as high as 26.1% (420 nm). Furthermore, by employing our ultrathin 2D BiVO4 NSs as the O-2-evolving photocatalyst, Ru-SrTiO3:Rh and Fe3+/Fe2+ as the H-2-evolving photocatalyst, and the redox mediator, respectively, a Z-scheme overall water splitting system is successfully constructed. Under visible light irradiation, our Z-scheme photocatalytic system presents high H-2 and O-2 evolution rates (16.7 and 8.0 mu mol h(-1)) with an AQY of 1.88% (420 nm) and good photocatalytic stability.