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Study on Preparation and Property of V2O5 /TiO2 Composite Film Via Microarc Oxidation

Author: LiXinWei
Tutor: CaiQiZhou
School: Huazhong University of Science and Technology
Course: Materials Processing Engineering
Keywords: micro-arc oxidation TiO2 film V2O5/TiO2 film photocatalyst rhodamine visible light response H2SO4 impregnate
CLC: TB43
Type: Master's thesis
Year: 2011
Downloads: 4
Quote: 0
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Abstract


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%.

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