pH对BiVO_4结构及其可见光催化活性的影响

Effect of p H on the Structure and Photo Catalytic Activity of BiVO_4 Driven by Visible Light

为考察pH对BiVO4晶体结构形貌及其可见光催化活性的影响,以Bi（NO3）3·5H2O和NH4VO3为原料,采用水热反应法（180℃）在不同pH下制备了系列BiVO4,并用亚甲基蓝作为模拟物测试BiVO4的可见光催化活性.XRD、SEM和UV-VisDRS分析表明：pH=5时,样品为片状纯单斜相BiVO4,带隙能较低,可见光响应较好;pH=2～4和pH=7～9时制备的是单斜相和四方相的混合相BiVO4,可见光响应较差.由此表明不同pH条件下制备的BiVO4样品晶型结构及光学性能显著不同,其中酸性过强或碱性过强均不利于单斜晶型BiVO4的生成.亚甲基蓝可见光降解实验结果表明：pH为5时制备的BiVO4对亚甲基蓝光解催化效果最好,可见光降解4h后降解率高达72.52%,而pH为2、3和9时BiVO4对亚甲基蓝的可见光催化降解率不到20.0%,说明制备溶液体系pH显著影响BiVO4的可见光催化活性.

In order to investigate the influence of p H on the structure and photo-catalytic activity of BiVO4 driven by visible light,Bi（NO3）3·5H2O and NH4VO3 were used as raw materials and a series of BiVO4 were synthesized by using the hydrothermal method（180℃）with different p H values. After that,methylene blue was used to evaluate the photo-catalytic activity of BiVO4. XRD,SEM and UV-Vis DRS analyses showed that the slice shape monoclinic crystal type of BiVO4 with lower band gap energy values and better visible-light responses could be obtained with p H of 5,whereas,the mixed type of tetragonal and monoclinic crystals of BiVO4 with worse visible-light responses were synthesized with pH of 2-4 and 7-9,respectively,which indicated that the crystal types of BiVO4 were evidently influenced by pH values. Moreover,results in this work showed that it was not good to prepare monoclinic crystal type of BiVO4 under too acidic or too alkali conditions. Additionally,test results of photo-catalytic degradation driven by visible light of methylene blue indicated that the excellent photo-degradation performance of methylene blue could be obtained with pH of 5,at which the degradation rate was 72.52%4 h after visible light irradiation,whereas,the degradation rate could not reach 20.0% with pH of 2,3 or 9,respectively,which further demonstrated that pH values had a great influence on the photo-catalytic activity of BiVO4.