Study On Preparation And Properties Of Bivo₄Photocatalytic Materials

With global energy crisis and environmental pollution problem getting serious,the synthesis and applications of visible-light photocatalyst to split water intohydrogen or to degrade organic pollutants, are becoming a hot research coveringmaterials science, chemistry and environmental science. As a new type of visible-lightactive photocatalyst, BiVO₄has obtained wide attention for its narrow energy bandgap and photocatalytic activity under the visible light irradiation.Using Bi（NO₃）₃·5H₂O and NH₄VO₃as raw materials, square monocline crystalBiVO₄photocatalyst were synthesized by hydrothermal method with CetyltrimethylAmmonium Bromide （CTAB） as surface-active agent. The as-prepared samples wereinvestigated by XRD, SEM, TEM, UV-VIS and BET. The effect of pH value,temperature, dwell time and the use level of surface-active agent on crystal structure,morphology and grain size of samples were studied. The results show that highlycrystallined monoclinic BiVO₄can be obtained via a hydrothermal route of110℃24h,with the recipe of Bi:V:CTAB=1:1:1in molar ratio, which possess highestphotocatalytic activity under the visible light irradiation. More than90%of RhB weredegradated after visible light irradiation for20min.BiVO₄was limited to further development and application in the field ofphotocatalysis for its lower utilization rate of light quanta, and higher recombinationrate of electronic-hole. To solve this problem, combined with the preparation methodof the single-phase BiVO₄, two ways of modification, semiconductor composite andion-doped method, were selected to carry out on the basis of the energy bandstructural analysis to get higher photocatalytic activity. One way is from compositeBiVO₄/BiOBr directly through changing reactants stoichiometric ratio and addingCTAB via precipitation and subsequently hydrothermal process and thenphotocatalytic activity were tested in photodegradation of rhodamine B. The resultshows that the degradation rate reached99%after visible light irradiation for20minwhen reactants stoichiometric ratio was Bi:V=1.1:1.The other choosed method is to dope N element in BiVO₄photocatalyst. Theresult shows that photocatalytic activity was improved and samples exhibit the betterphotocatalytic activity than the other samples when the adding volume of N is20%under the same conditions. Above or below this content is not conducive to playphotocatalytic activity. It is considered that both semiconductor composite and iondoping can improve the utilization efficiency of light quanta by lower recombinationrate of electronic-hole and then, the catalytic performance is significantly improved.