Preparation And Photocatalytic Activity Research Of Bismuth Vanadate Series Compound Semiconductor Materials

The energy crisis and environmental pollution increasingly serious, the traditional pollution treatments need much energy and complex equpment, high cost and easy to pollute the environment the second time. The research of semiconductor photocatalysts has caused wide public concern over the recent years. Bismuth vanadate, as a new photocatalyst, has narrow energy gap and wide region of photorespone under visible light. It has huge potential in degradation of organic pollution under visible liget irradiation, but its bad absorbability and high recombination rate of photoproduction electron-hole pairs limt its practical application in a large part. Now, the commonly used method to improve the separation of electron-hole pairs consists mainly of morphology control, noble metal deposition or coupling with other semiconductor, could efficiently improve its photocatalytic activity. The crystal exposed bismuth vanadate has just been attended. It can realize the transfer of the photoproduction electron-hole pairs between the different facets of the crystal exposed bismuth vanadate. This phenomenon can largely increase the separation rate of electron-hole pairs so that the crystal exposed bismuth vanadate can be considered to be a kind of huge potential base material because their own performance is very good. Now, the crystal exposed bismuth vanadate has become a hot research topic because of its simple preparation method, low cost, high production and good stability. The seriously agglomerate phenomena in the preparation process of crystal expose bismuth vanadate become a very difficult problem to solve, so the foucs on research must be looked for appropriate solutions to solve the problem of agglomerate phenomena. Therefore, looking for an effective method to solve the problem of reunion in the process becomes the top idea of the photocatalyst research.In this paper, the crystal exposed Bi VO4 with high photocatalytic activity has been successfully prepared by conventional hydrothermal based on Bi(NO3)3·5H2O as the source of bismuth, NH4VO3 as the source of vanadium, the different influences of reaction time and reaction temperature on the crystal phase and the microstructure have been discussed; the(110) and(010) facets exposed Bi VO4 with high dispersibility has been successfully fabricated by conventional hyderothermal based on Bi(NO3)3·5H2O as the source of bismuth, Na VO3·2H2O as the source of vanadium. The different volume of addition of glacial acetic acid has been discussed; The Bi VO4/Ag2 O compound photocatalyst with high visible-light photocatalytic activity has been preparated by a impregnation-evaporation method, the crystal exposed Bi VO4 was used as the basis materials, the different loading capacity of Ag2 O has been discussed; Novel dumbbell-like Bi VO4/Cu O heterogeneous nanostructures with enhanced visible-light photocatalytic activity has been successfully prepared by microwave method and impregnation-calcination technique. The phase composition of all of the as-prepared samples was tested by XRD, the micro morphology was observed by SEM, the light absorption property was measured by UV-vis. The photocatalytic activity of methyl orange photodegradation has been discussed, a 500 W Xe lamp was used as the source visible light. The photocatalysis experiments show that the photodegradation rate of methyl orange is closely related to the crystal structure, micro morphology and light absorption property. The growth mechanism of as-preparaed crystal exposed Bi VO4 and the reasons of high photocatalytic activity of composite photocalyst have been discussed.The results show as follows:(1) The morphology of as-preparaed crystal exposed Bi VO4 with Bi(NO3)3·5H2O as the source of bismuth, NH4VO3 as the source of vanadium was irregelular polyhedron, with higher reaction temperature, the irregelular polyhedron can be made to assemble themselves and become 3dimensional sphere, the more facets are exposed; The as-preparaed samples with no glacial acetic acid added have a decahedral morphology, but seriously agglomeration phenomenon is observed by SEM. In order to solve the agglomeration phenomenon, the glacial acetic acid was added into the precursor solution, when the addition of glacial acetic acid is 1m L, the Bi VO4 samples show high dispersibility, we finally get the(110) and(010) facets exposed Bi VO4 with high dispersibility.(2) The Bi VO4/Ag2 O composite photocalyst shows high light absorption property under visible-light region, which use the(110) and(010) facets exposed Bi VO4 samples as the basis materials. A large number of nano p-n junction heterostructures which assembled by p-type Ag2 O nanoparticles formed on the surface of Bi VO4 nanocrystals, where Ag2 O and Bi VO4 formed p- and n-type semiconductors, respectively. In addition, the p-n junction Bi VO4/Ag2 O heterogeneous nanostructures have much higher photocatalytic activities than the pure Bi VO4 nanocrystals for the degradation of methyl orange under visible light irradiation. The enhanced photocatalytic activity owed to the effective charge transfer from different crystal facets and p-type Ag2 O to the attached n-type Bi VO4 nanoparticles,When the loading capacity was 20%, the composite photocatalyst shows best photocatalytic activity.(3) The dumbbell-like Bi VO4 which preparaed by microwave hydrothermal is assembled by plenty of nanoparticles. This p-n junction of Cu O/Bi VO4 heterogeneous nanostructures can promote the light absorption capability of photocatalyst and separation of excited electron-hole pairs. The photocatalytic experiments show that Cu O loading can effectively enhance the photocatalytic activities of the samples which are evaluated by the degradation of methyl orange under visible-light irradiation.