BiVO4纳米结构的形貌和组成控制及其对光催化性能的影响

Morphology and Composition Control of BiVO4 Nanostructures and Their Effects on Photocatalytic Properties

在不采用表面活性剂的情况下,通过简易的水热法合成了单斜相的BiVO4纳米结构。研究结果表明,pH值和反应时间是决定产物形貌和组成的两个重要因素。通过控制pH值,调控了BiVO4的形貌和制备过程中杂质的生长速率。由于酸性环境可以抑制杂质的生长,并且杂质生长速率会随着pH值的升高而加快,因此在pH值为3和5、不同反应时间(6、10、14 h)下都可以合成纯单斜相的BiVO4样品。然而,随着pH值(pH值为7和9)的增加和反应时间的延长,产物中杂质出现的概率会不断增加。因此,要得到纯单斜相BiVO4,pH值和反应时间这两个因素都应控制在适当的范围内。固定反应时间为6 h,不同pH值(pH值为3、5、7和9)下产物的聚集程度逐渐升高,形貌从松散颗粒逐渐向高聚集形态演变,分别得到亚微米级颗粒、纳米粒子包覆多孔核结构和微米管状结构。光催化行为测量结果表明,pH值为7时得到的BiVO4样品的粒径小、为多孔结构、比表面积大、可见光吸收度高、分散良好及可见光辐射下其在亚甲基蓝(MB)溶液中具有最佳的光催化活性,其降解效率在辐射40 min后约为94%。

Monoclinic BiVO4 nanostructures were synthesized by the facile hydrothermal method without surfactants.The research results show that the pH value and the reaction time are two important factors determining the morphology and composition of the final product.The pH value can be used to adjust the product morphology and the growth rate of the impurity in the preparation process.Because the growth rate of the impurity was suppressed in an acid environment and was accelerated gradually with the increased pH value,the pure monoclinic BiVO4 samples were synthesized for different reaction time(6,10 and 14 h)at pH values of 3 and 5.However,it is demonstrated that more impurities would appear in products along with the increases of pH value(7 and 9)and reaction time.Therefore,in order to obtain the pure monoclinic BiVO4,both the pH value and the reaction time should be controlled in appropriate ranges.When the reaction time was fixed at 6 h,the aggregation of the products at pH values of 3,5,7 and 9 increased gradually,and the products exhibited morphological evolution from loose particles to high aggregation level,where submicron particles,nanoparticles coating on porous cores and micro tubes were prepared,respectively.Photocatalytic behavior measurement results indicate that the BiVO4 sample obtained at pH=7 is of small particle size,porous structure,large specific surface area,high visible light absorption and good dispersion,and has the best photocatalytic activity in the methylene blue(MB)solution under visible light irradiation,whose degradation efficiency was^94% after the irradiation for 40 min.