The upconversion and enhanced visible light photocatalytic activity of Er3+-doped tetragonal BiVO4

Er3+-doped BiVO4 with tetragonal structure is prepared by the micro-wave hydrothermal method. X-ray diffraction and Rietveld refinement demonstrate that the structure is transformed from the monoclinic (C2/c:c3) phase to the tetragonal (I41/amd:2) phase by doping with Er3+ ions. Er3+ doping also influences themorphology change of BiVO4 from irregular flake-like crystal to rod-like crystal, which leads to the increase of the surface areas from 3.25 to 11.96 m(2) g(-1). Compared with the monoclinic BiVO4, the upconversion of the Er3+-doped tetragonal BiVO4 occurs through the transitions from the I-4(15/2) ground state to F-4(7/2), H-2(11/2), and F-4(9/2) states, respectively. The photocatalytic experiment indicates that the tetragonal BiVO4 (8 at.%) with a larger specific surface area (9.88 m(2) g(-1)) shows the best photocatalytic activity under visible light irradiation, which can efficiently improve the degradation rate of RhB up to 97.2% at 150 min.