Enhanced photocatalytic activity and dielectric property of c-axis oriented Bi2VO5.5 thin film by Gd3+ doping

Bismuth-layered perovskite Bi2−xGdxVO5.5 (x=0, 0.02, 0.04, 0.06, 0.08, and 0.10) thin films with preferred c-axis orientation were deposited on fused silica substrates by using a chemical solution deposition method. The X-ray diffraction, scanning electron microscopy, optical measurements of the thin films were characterized and the photodegradation of Methylene Blue was used as a probe reaction to test the photocatalytic activities of the Bi2−xGdxVO5.5 thin films. The thin films were also deposited on Pt(111)/Ti/SiO2/Si substrates by the same method to measure their dielectric properties. With increasing Gd3+-doping content x, the photoactivity of the thin film increased, and the optimum activity appeared when the value of x was 0.08. The degradation rate of Methylene Blue obtained was 90% when the solution was irradiated under UV light for 3 h with the existence of Bi1.92Gd0.08VO5.5 thin film. The reason for the enhancement originates from the two positive factors. One is the electron trap generated by the special 7f electronic configuration of Gd3+ which could increase the separation of the photoinduced electron hole pairs. The other is that the Debye length increases with the increase of dielectric constant of the thin films, and then the width of the space charge region in the solid–liquid interface is broadened, which will make more photoinduced carriers available for the catalytic reaction. The results above indicate that the Bi2−xGdxVO5.5 thin films are promising candidate materials for environmental pollution control.