Synthesis of square Bi2WO6 nanoplates as high-activity visible-light-driven photocatalysts

Square Bi2WO6 nanoplates have been successfully synthesized by simple hydrothermal process. The effects of hydrothermal temperature and reaction time on morphologies and sizes of the nanoplates were investigated. These nanoplates are square geometric shapes having their basal plane as the (001) plane of orthorhombic Bi2WO6. On the basis of results of morphologies observation and selected area electron diffraction of series samples, a possible growth mechanism of the nanoplates is revealed. The square laminar shape could be attributed to anisotropic growth along the (001) plane, which is parallel to their intrinsic layer structure. UV-visible diffuse reflection spectra of the prepared Bi2WO6 nanoplates indicate they had absorption in the visible region, but a blue shift appeared compared to their bulk counterparts. Their photocatalytic activities are determined by rhodamine B degradation under visible light irradiation (lambda > 400 nm). The reaction constant (k) of the best quality Bi2WO6 nanoplates is three times that of the sample prepared by solid-state reaction, which indicates much higher photocatalytic activities of the nanoplates performed under visible light irradiation.