Enhanced Photocatalytic Activity of Ag3VO4 Loaded with Rare-Earth Elements under Visible-Light Irradiation

Rare-earth-loaded Ag3VO4 catalysts (RE3+-Ag3VO4, RE = Nd, Sm, and Eu) were prepared by the wetness impregnation technique and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), diffuse reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the samples were evaluated by rhodamine B (RhB) dye degradation under visible-light irradiation. It was found that the presence of rare-earth oxides in the host Ag3VO4 could decrease the band gap and accelerate the separation of photogenerated electron−hole pairs, which led to higher photocatalytic activities. Among the rare-earth-loaded samples, Nd3+-loaded Ag3VO4 catalyst showed the highest photocatalytic activity. The optimum contents of Nd3+, Eu3+, and Sm3+ were found to be 2, 3, and 2 wt %, respectively. It was also found that the photocatalytic degradation of RhB over RE3+-Ag3VO4 (2 wt %) followed pseudo-first-order kinetics. A possible mechanism for RhB photocatalytic degradation over RE3+-Ag3VO4 catalysts is also proposed.