Characterization and the removal efficiency of Rhodamine B by monoclinic and hexagonal WO3 with oxidized and partially reduced states

Understanding the relationship between crystal structures, oxidation state and photocatalytic activity is the core issue in metal oxide to achieve desired performance. Herein, we present monoclinic (m-WO3) and hexagonal WO3 (h-WO3) with different tungsten oxidized states via acid precipitation process followed by different thermo-decomposition treatment. A systematic study of the removal of Rhodamine B from aqueous solution under UV light irradiation has revealed that the photocatalyic activities of WO3 are strongly dependent on their crystal structures. After irradiation, 22%, 48%, 80% and 76% of RhB removal efficiency were achieved by the m-WO3, m-WO3-x, h-WO3 and h-WO3-x, respectively. Monoclinic WO3 with partially reduced state exhibited higher activity than that of m-WO3 with oxidized state. However, the oxidation state of tungsten has no significant effect on the photocatalytic activity of h-WO3.