Facile one-pot solvothermal preparation of Mo-doped Bi₂WO₆ biscuit-like microstructures for visible-light-driven photocatalytic water oxidation

The adsorption behavior and the separation efficiency of photogenerated electron-hole pairs are two important elements in estimating the photocatalytic activity of a photocatalyst. In this work, we have developed a facile one-pot solvothermal method for the preparation of Mo-doped Bi₂WO₆ with uniform three-dimensional (3D) hierarchical porous biscuit-like microstructures (PBMs). Mo doping is found to have two important roles in the synthesis of Bi₂WO₆ particles, leading to porous microstructures and adjusting band gaps of the Bi₂Mo_xW_1-xO₆ particles. The band structure of the as-prepared porous Bi₂Mo_xW_1-xO₆ products is characterized by UV-vis diffuse reflectance spectroscopy and valence-band X-ray photoelectron spectroscopy. Density functional theory (DFT) calculations give further insights into the band structure of the Bi₂Mo_xW_1-xO₆ products. In all the samples, Bi₂Mo_0.21W_0.79O₆ PBMs exhibit a very efficient catalytic performance in oxidizing water under visible light irradiation (λ > 420 nm), with an average O₂ evolution rate of up to 147.2 μmol h^-1 g^-1 and an apparent quantum efficiency (QE) of 3.1% at 420 nm, representing a 2 times more enhancement compared with the non-doped Bi₂WO₆ sample. This study provides a simple method for designing metal-doped semiconductors with porous structures for different applications.