Study On Preparation And Property Of V₂O₅ /TiO₂ Composite Film Via Microarc Oxidation

TiO₂ photocatalyst can only absorb in the UV region of the solar spectrum due to its wide band gap. The use ratio of solar spectrum is low. The photocatalysis ratio of TiO₂ was low because of its high recombination rate of photo-induced carrier. On the other hand, TiO₂ photocatalyst is applied in form of powder at present stage. The powders aggregate easily, and it is difficult to collect and recycle. These deficiencies restrict the applications of TiO₂ photocatalyst. Therefore, the catalyst loading process, expenditon of photoresponse region and enhance of photocatalysis activity are important research trend for TiO₂ photocatalyst.In this paper, Micro-arc Oxidation (MAO) was adopted to prepare visible response V₂O₅/TiO₂ composite photocatalyst. The surface and cross-section morphologies, the element distribution and the phase composition of coatings were analyzed by means of SEM, EDX and XRD. The effect of electrolyte composition on the microstructure, the phase composition and surface morphology was studied. The degradation rate of rhodamine was investigated, and the modification mechanism of vanadium on TiO₂ composite film was discussed. The following results were obtained.The TiO₂ film and V₂O₅/TiO₂ compound coating were prepared on titanium in Na₃PO₃ electrolyte and NaVO3 electrolyte. The MAO film from Na₃PO₃ electrolyte had a porous surface, and consisted of anatase TiO₂ and rutil TiO₂; the MAO film from NaVO3 electrolyte had less holes, higher roughness and consisted of anatase TiO₂, rutil TiO₂ and V₂O₅. The degradation rate of rhodamine of MAO coating in NaVO3 electrolyte increased to 42% from 13% in Na₃PO₃ electrolyt in UV-light irradiation.Titanium was treated with MAO in NaVO3 electrolyte. The content of V in the films was enhanced along with increasing the consistency of NaVO3. The absorbtion edge of the film abtained a abvious red-shift by the enhancer of vanadium, but the red-shift was reduced when the content of vanadium was excessive. The absorbtion edge of the film was 603nm when NaVO3 was 8.54g/L. The highest degradation rate of rhodamine was 93% in visible light. XPS analysis showed vanadium in the film had two kind of chemical valence, V5+ and V4+ which indicated the motification to TiO₂ film came from the adulteration of V4+ and the compound between V₂O₅ and TiO₂. A linear relation between the degradation rate of rhodamine and time which cohered with pseudo first order reaction showed that the photocatalytic capability of V₂O₅/TiO₂ compound film was steady.V₂O₅/TiO₂ compound film became rougher after impregnated with dilute sulphuric acid. The analysis of EDX and XRD showed that dilute sulphuric acid dissolved the V₂O₅ on the surface of the V₂O₅/TiO₂ compound film. when XPS showed the impregnated film contained defect oxides (Ti-O-V). Impregnation with dilute sulphuric acid made the absorbtion edge have a blue-shift from 603 nm to 440 nm, but the degradation rate of rhodamine in visible light for 14 h was enhanced from 84% to 93%.