Preparation Of Er-doped TiO₂ Films And The Study Of Their Photocatalytic Activity

The photocatalytic technology has a promising prospect in applications because its unique advantages in the fields of solar energy conversion and environment protection. The waste water from industry and agriculture contains kinds of organic pollutants that is harmful and very difficult to be degraded. TiO2 thin films can degrade and mineralize the organic pollutants completely without secondary pollutions and overcomes the shortcomings of agglomeration, difficulties in separation and recycles in solution system of TiO2 catalyst powers. TiO2 can only be activated by ultraviolet light with higher energy owing to the broad band gap. Unfortunately, ultraviolet is only 5% of solar light. By doping ions, the optical response range of the modified TiO2 can be widen to the visible light region, which can improve the utilization of sunlight effectively for TiO2 films. Few studies were reported on the preparation of erbium-doped titanium dioxide films and their photocatalytic properties under simulated solar light.In the paper, sol-gel method was used to synthesis the Er-doping TiO2 sols with Er(NO3)3·5H2O as the source of Er element, then the dip-spin-coating technique was adopted to prepare the Er-doping TiO2 films on the surface of round glass. Subsequently, with span80 as addictive, the modified Er-doping TiO2 films were obtained by the same methods. The effect of preparation conditions on the films structure was studied. The methyl orange solution was choosed to simulate azo dyes waste water, and the photocatalytic performance of the films was inverstigeted by the photocatalytic degradation of MO. The properties of films were characterized by X-ray diffraction, Scanning Electron Microscopy, ultraviolet-visible diffused reflectance, thermal analysis, Nitrogen adsorption method. The results are as follows:1, Sol-gel method and the dip-spin-coating technique were used to synthesis the Er-doping TiO2 films on the substrate of glass with Er(NO3)3-5H2O as the source of Er. The effects of different conditions were studied. Increasing the number of film layers results in the increased of the nanoparticles content. Er-doping can inhibit the growth of grain and crystal phase transition, meanwhile, the Er-doping TiO2 films can absorb the visible light. Higher calcination temperatures of the films favor to improve the degree of crystallinity of the particles, and the calcination time does not affect the crystal structure, almost has no effect on grain size.2, The photocatalytic properties of erbium-doped titania thin films were studied with xenon lamp (simulated sunlight) as the light source, the results showed that:when coating layers was four, erbium content 1.0at%, calcination temperature 500℃, calcination time 1h, the Er-doping TiO2 film has the highest activity and the degradation rate (6h) of methyl orange was 53.3%.3, The modified porous erbium-doped titanium dioxide thin films were prepared with the surfactant span80 as additive and erbium content 1.Oat% with the dip-spin-coating technique. By adding span80, the size of the particles in the film reduced, and the surface of films is continuous, but the morphology of the film is changed. The films prepared with span80 as additive had the higher specific surface area. Photocatalytic experiments results show that when ω(span80)=0.3wt% in the synthesis sol, the membrane has the highest photocatalytic activity, and the degradation rate (6h) of MO was 56.9%, much better than the film without addition span80.