Zinc tungstate: a review on its application as heterogeneous photocatalyst

ZnWO4 crystallizes in a monoclinic wolframite-like structure, which has been studied for applications in heterogeneous photocatalysis for degradation, oxidation, and reduction of various contaminants. This type of tungstate has proved to be an efficient photocatalyst under both ultraviolet and visible light irradiation and, when ZnWO4 forms a heterostructure with other semiconductors or when it is doped with different ions, it has a great efficiency under sunlight irradiation. For instance, the optimization of ZnWO4 efficiency has been attained by its heterojunction with different semiconductors such as ZnO, one of the most used materials for this purpose, but also with other compounds such as BiOBr, FeWO4, TiO2, WO3, Bi2WO6, among others. In addition, doping ZnWO4 with the Ti4+, Bi3+, Ce3+, and Co2+ metal ions or with nonmetals (F- and N3-) can also increase the photocatalytic yield of the material. The photocatalytic properties of ZnWO4-based catalysts have been explored toward inorganic and organic molecules. However, among the variety of target molecules, organic pollutants such as methylene blue, methyl orange, and rhodamine B dyes appear as the most investigated in studies involving photocatalysis in the presence of ZnWO4. In our review, we summarize important literature works, highlighting the advancement in photocatalysis using ZnWO4.