Nanosheet-based Bi₂Mo_xW_{1- x}O₆ solid solutions with adjustable band gaps and enhanced visible-light-driven photocatalytic activities

Bi₂Mo_xW_1-xO₆ solid solutions with various compositions (x = 0, 0.25, 0.50, 0.75, and 1.00) have been synthesized by a facile hydrothermal crystallization method. All the as-synthesized products are composed of nanosheets with similar orthorhombic Aurivillius layered structures. With decreasing Mo content, the thickness of the nanosheets decreases. The nanosheets begin to intergrow at x = 0.75 and further assemble into hierarchical superstructures through "oriented attachmenta" with even less Mo content. For the Bi₂Mo _xW_1-xO₆ solid solutions with x = 0.25, 0.50, and 0.75, the valence band is widened and the conduction band is elevated when compared with the most intensively studied Bi₂WO₆ photocatalyst. As a result, the Bi₂Mo_xW _1-xO₆ solid solutions (x = 0.25, 0.50, and 0.75) show narrowed band gaps of a2.69 eV when compared with Bi₂WO₆ (2.94 eV) and Bi₂MoO₆ (2.72 eV). The photocatalytic activities of the as-prepared products have been evaluated using the photodecomposition of methylene blue under visible light irradiation as a model reaction. The sample, Bi₂Mo_0.25W_0.75O ₆, exhibits the highest photocatalytic activity. The intrinsic layered structure, nanosheet morphology, manipulated band structure and band gap, and the W content play important roles in the photocatalytic activity. Our approach provides a facile technique to tune both the nanostructure and the band gap of photocatalysts by simply adjusting the composition of the solid solutions, leading to photocatalysts with enhanced visible light photocatalytic activity. This method may be further extended to the designed synthesis of novel and highly efficient visible-light-driven semiconductors for environmental remediation.