The Study On Photocatalytic Degradation Of Organic Contaminants By Titania-doped Composites

TiO₂and polyoxometalates （POM） have been widely used in the photocatalytic reactionwith the advantages of high catalytic activity, non-toxic etc. In this paper, TiO₂with dominant（001） facets has been synthesized by hydrothermal method using titanium tetrachloride andtetrabutyl titanate as titanium source and hydrofluoric acid as a morphology controlling agent.N-doped、nitrogen fluorine-doped titanium dioxide have been successfully synthesized usingurea and ammonium fluoride as the nitrogen sources, respectively, the catalytic activity ofwhich under visible light has been investigated. POM/TiO₂composites have been in situprepared to use four kinds of typical POM and TiO₂. All the samples have been characterizedby transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, X-raypowder diffraction （XRD） and Raman spectroscopy （Raman）. Their photocatalytic propertieshave been also studied with degradation of rhodamine B as a probe. The results weresummarized as follows:1. N-doped titanium dioxide with dominant （001） facets has been successfully preparedwith urea as the nitrogen source. The results showed that anatase TiO₂and N-TiO₂made up ofsheet-like structures, and TiO₂still retained anatase phase after calcined at900°C. Therefore,the fluorine ions not only had a specific stabilization effect on the （001） facets, meanwhilesuppressed the crystallization of TiO₂into rutile phase at higher temperature. N-TiO₂hadstrong absorption in the visible region. Using degradation of rhodamine B solution as a probe,photocatalytic activity has been significantly improved. When the mass ratio of N/Ti was5%,visible light photoactivity of N-TiO₂is highest.2. Nitrogen fluorine-doped titanium dioxide with exposed （001） facets have been preparedusing NH4F as the nitrogen source. The results indicated that the anatase phase of TiO₂hasbeen retained by nitrogen fluorine doping. The N, F-TiO₂anatase nanosheets have response inthe visible light range. Compared with undoped TiO₂, the photocatalytic activity of N, F-TiO₂has been greatly increased. When the mass ratio of N/Ti is25%, the photocatalytic activitywas best.3. POM/TiO₂composites have been synthesized to use four kinds of typical POM and TiO₂.Test results demonstrated that anatase POM/TiO₂made up of nanosheets. Compared withundoped TiO₂, the photocatalytic activity of POM/TiO₂has been greatly improved, whichmay be due to the synergy between the POMs and TiO₂. The recombination of photoinducedelectrons and holes was inhibited effectively; thereby photocatalytic activity of POM/TiO₂composites was increased.