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

Abstract

Er³⁺-doped BiVO₄ with tetragonal structure is prepared by the microwave 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 the morphology 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 m² g⁻¹. Compared with the monoclinic BiVO₄, the upconversion of the Er³⁺-doped tetragonal BiVO₄ occurs through the transitions from the ⁴I_15/2 ground state to ⁴F_7/2, ²H_11/2, and ⁴F_9/2 states, respectively. The photocatalytic experiment indicates that the tetragonal BiVO₄ (8 at.%) with a larger specific surface area (9.88 m² 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.