Enhanced photocatalytic activity of Gd-doped porous β-Bi2O3 photocatalysts under visible light irradiation

Gd-doped porous beta-Bi2O3 microspheres with different Gd concentrations (at.% = 0, 1, 2, 3 and 4%) were prepared by a simple hydrothermal synthesis method and characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, the Brunauer-Emmett-Teller surface area, UV-vis adsorption spectroscopy and photoluminescence measurements. Two types of dyes, anionic methyl orange (MO) and cationic Rhodamine B (RhB) dyes, were chosen as model pollutants to evaluate the photocatalytic activity of the as-prepared samples. The results indicated that the photocatalytic performance of the samples was significantly enhanced with the doping of Gd3+ ions. The 2 at.% Gd-doped beta-Bi2O3 sample exhibited the highest photocatalytic activity compared with other samples. In addition, phenol as a colorless pollutant was also chosen to further study the photocatalytic activity of pure beta-Bi2O3 and Gd-doped beta-Bi2O3 samples. The 2 at.% Gd-doped beta-Bi2O3 also showed much higher photocatalytic activity for the photodegradation of phenol than pure beta-Bi2O3. The mechanisms for photodegradation of RhB and MO over the Gd-doped porous beta-Bi2O3 photocatalysts under visible light irradiation were also discussed in detail. The enhanced photocatalytic activity could be attributed to the effective separation of photo-induced electron-hole pairs for Gd3+ served as an efficient scavenger to trap photo-generated electrons. (C) 2015 Elsevier B.V. All rights reserved.