Influence of Crystal Water on Crystal Structure, Electronic Structure, Band Structure, and Charge Separation of WO3·2H2O Nanosheets

In this work, we mainly investigate the influence of structure water on crystal structure, electronic structure, band structure, and charge separation of WO₃·2H₂O. It is found, for the first time, that although water is a weak electron donor, a ligand-to-metal charge transfer (LMCT) from H₂O to W occurs. The structure water contributes to the conduction band (CB) of WO₃·2H₂O, and the band gap of WO₃·2H₂O is obviously narrowed, thus increasing the light absorption obviously. Moreover, the results of EIS, photocurrent spectra, and PL show that structure water in WO₃·2H₂O also improves the charge separation and transfer efficiency of the catalyst. This is the first investigation on the LMCT transfer from structure water (a weak electron donor) to tungsten, which obviously improves light absorption and charge separation. Under visible light irradiation (λ ≥ 420 nm), WO₃·2H₂O nanosheets have a photocatalytic activity 2.3 times higher than that of WO₃ for the degradation of methylene blue (MB). The kind number of photochemical materials can be increased greatly, because structure water-contained compounds widely exist in nature.