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As a novel visible-light-driven photocatalyst, Yb 3 + /Ho 3 + co-doped Bi 2 WO 6 (Yb 3 + /Ho 3 + -Bi 2 WO 6 ) was synthesized via a simple hydrothermal method and subsequent a calcination process. The as-synthesized Yb 3 + /Ho 3 + -Bi 2 WO 6 samples were characterized by various analytical methods. The BIW-5 (Yb 3 + /Ho 3 + molar ratios is 5) sample showed the highest photocatalytic activity. The RhB was degraded (99.8%) under visible light irradiation in 20 min. The improved photocatalytic activity could be attributed to the efficient energy transfer between Yb 3 + /Ho 3 + and Bi 2 WO 6 via infrared to visible upconversion and the reduced combination rate of photogenerated electron-hole pairs through doping Yb 3 + /Ho 3 + ions. Therefore, this study may provide a better method to obtain stable upconversion photocatalyst with greatly improved activity. [ABSTRACT FROM AUTHOR]

• A series of Tm3+/Yb3+-Bi 2 WO 6 catalysts hydrothermally prepared and characterized. • Tm3+/Yb3+-Bi 2 WO 6 showed excellent optical properties. • Significantly enhanced photocatalytic activity is achieved when degrading RhB. • This study provides a great way to obtain stable photocatalyst. Tm3+ and Yb3+ co-doped Bi 2 WO 6 up-conversion photocatalysts (Tm3+/Yb3+:Bi 2 WO 6) were synthesized via co-precipitation route at different calcination temperatures. Doping Tm3+ and Yb3+ into Bi 2 WO 6 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+:Bi 2 WO 6 exhibited a much superior photocatalytic activity than the pure Bi 2 WO 6 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 Bi 2 WO 6 were studied in detail. The improved photocatalytic activity of Bi 2 WO 6 could be attributed to the efficient energy transfer between Tm3+/Yb3+ and Bi 2 WO 6 via infrared to visible up-conversion and the reduced recombination rate of photogenerated electron-hole pairs through co-doping of Tm3+/Yb3+ on Bi 2 WO 6 nanopaticles. [ABSTRACT FROM AUTHOR]