Preparation And Photocatalytic Property Of Bi₄Ti₃O₁₂-Based Heterojunction Nanomaterials

The traditional energy crisis and the problem such as water pollution are serious threats to human survival and development, and thus exploring renewable energy and finding effective measures to control water pollution become very important. It is found that the degradation of organic pollutants using semiconductor photocatalyst has very broad application prospect. However, the technology still has some problems, such as the low catalyst quantum efficiency, the rapid recombination of photoinduced electrons and holes, poor light stability, difficult to separate for recycling, difficulties of batch production application and so on. Therefore, development of high activity, good stability, easy recovery, low cost and easy synthesis of photocatalyst is the key of the photocatalytic technology application. In this paper, we focus on development of Bi4Ti3O12-based heterojunction nanomaterials of high catalytic activity, combining the electrostatic spinning technology with hydrothermal(solvothermal) and in situ ion exchange methods to control their composition and morphology to solve the above problems.Two kinds of Aurivillius oxide semiconductor heterostructures based on Bi4Ti3O12 nanofiber frameworks and Bi2XO6(X = Mo, W) nanosheets are successfully synthesized by combining the electrospinning technique and solvothermal method. The intimate interface between Bi4Ti3O12 nanofibers and Bi2MoO6 or Bi2WO6 nanosheets forms in the heterojunctions from the high-resolution transmission electron microscopy measurements. The Bi4Ti3O12/Bi2XO6(X = Mo, W) heterostructures possess a high degradation rate of Rhodamine B(RB) under visible light, mainly owing to the photoinduced interfacial charge transfer based on the photosynergistic effect of the Bi4Ti3O12/Bi2XO6 heterojunction. Due to the large length to diameter ratio of nanofibers the heterostructures can be recycled easily by sedimentation without a decrease of the photocatalytic activity. Moreover, such simple and versatile strategy can provide a general way to fabricate other heterostructures of Bi(III)-containing oxides, such as Bi4Ti3O12/BiVO4 and Bi4Ti3O12/BiOCl.Through a simple in situ ion-exchange reaction between the Bi4Ti3O12 nanofibers and thioacetamide, Bi4Ti3O12/Bi2S3 hierarchical heterostructures were successfully fabricated. Controlled partial ion exchange brings about the close interconnectionbetween the semiconductors to benefit the separation of carriers. The Bi4Ti3O12/Bi2S3 heterostructures exhibited enhanced photocatalytic performance under visible light. The improved photocatalytic activities are attributed to the visible light absorption enhanced by Bi2S3 and the formation of a heterojunction between Bi4Ti3O12 and Bi2S3, which can effectively accelerate the charge separation and transfer.