Novel Tm3+ and Yb3+ co-doped bismuth tungstate up-conversion photocatalyst with greatly improved photocatalytic properties

Tm3+ and Yb3+ co-doped Bi2WO6 up-conversion photocatalysts (Tm3+/Yb3+:Bi2WO6) were synthesized via co precipitation route at different calcination temperatures. Doping Tm3+ and Yb3+ into Bi2WO6 lattice and substituting for the fractional Bi3+ were successfully confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. The morphology and optical property of the obtained samples were characterized by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV vis diffuse reflectance spectra (DRS) and up-conversion luminescence spectra (UC-PL). The photocatalytic results revealed that the Tm3+/Yb3+;Bi2WO6 exhibited a much superior photocatalytic activity than the pure Bi2WO6 and commercial Degussa P25 for the degradation of rhodamine B (RhB), and the degradation rate reached 97.6% in 25 min. The effects of Tm3+ and Yb3+ on the photocatalytic activity of Bi2WO6 were studied in detail. The improved photocatalytic activity of Bi2WO6 could be attributed to the efficient energy transfer between Tm3+/Yb3+ and Bi2WO6 via infrared to visible up-conversion and the reduced recombination rate of photogenerated electron-hole pairs through co-doping of Tm3+/Yb3+ on Bi2WO6 nanopaticles.