Synthesis of Bi-deficient monolayered Bi2WO6 nanosheets with enhanced photocatalytic activity under visible light irradiation

Surface defects in materials usually play pivotal roles in photocatalytic processes as they can provide extra active sites and tune the band structure of semiconductors. Researchers have paid much attention on oxygen vacancies in catalysts, however, very little work has been reported on the role of metal vacancies in semiconductors in the field of photocatalysis. In this study, bismuth vacancies were introduced into monolayered Bi2WO6 nanosheets through a facile hydrothermal method under acidic conditions. The 1.0 M-mBWO sample with an appropriate defect concentration exhibited the most excellent visible-light photocatalytic performance for the removal of gaseous toluene among all the samples, and possessed a k value that was 32 times larger than that of pristine monolayered Bi2WO6. The characterization results demonstrated that an appropriate amount of bismuth vacancies in the lattice could greatly enhance the separation ratio of the photoexcited electron-hole pairs, ensuring better photocatalytic performances. Such high separation ratios of electron-hole pairs could be mainly attributed to the formation of strong protonated hydroxyl groups around bismuth vacancies, which would allow the trapping of photogenerated electrons in vacant sites. This study might open up a new route to design other advanced materials with metal vacancies for photocatalytic applications.