二维负载型ZnO/BiOBr(1-x)Ix超薄异质结构增强光催化降解活性机制研究

The photocatalysis is an ideal technique for environment pollution treatment and clean energy production (Hydrogen energy). It is a valid route for enhancing quantum efficiency during photocatalysis by building internal electric field to separate photo-generated electrons and holes. However, photocatalytic activity is still bound due to the mutual restriction between the formation requirement of build-in electric field and the size of photocatalyst. Such conflict is the key to limit the extent of spreading and application of photocatalysts with built-in electric field. Two-dimensional-loaded ultrathin heterostructures can separate photo-generated electrons and holes by potential gradient from junction region and non-junction one on its surface, which is not affected by the size of photocatalyst. Therefore, this object is to design and fabricate two-dimensional BiOBr(1-x)Ix(x=0~1) nanosheets-loaded porous ZnO ultrathin films via a chemical self-assembling route; investigate influencing factors of surface potential gradient of two-dimensional-loaded ultrathin heterostructures and its effects on photogenerated charges, employing Kelvin probe force microscopy; reveal preliminarily the mechanism of two-dimensional-loaded ultrathin heterostructures enhancing photocatalytic activity. This proposal is aimed to seek a method to inhibit the recombination of photo-induced carriers remaining large specific surface of photocatalysts so as to provide basic theory and technique for obtaining sunlight-driven photocatalyst with high performance.

光催化技术是一种理想的环境污染治理技术和洁净能源（主要指氢能）生产技术。通过不同材料的复合构建内电场促进光生电子与空穴的分离是提高光催化量子效率的有效途径。然而，复合材料内建电场的形成与其颗粒尺寸相互牵制导致光催化活性提高有限，这一矛盾成为制约该项技术推广应用的主要瓶颈。二维负载型超薄异质结构可以利用横向上表面结区与非结区的势差驱动光生电荷的分离而不需受纵向上尺寸的限制。因此，本项目采用化学组装技术设计合成一系列二维负载型ZnO/BiOBr(1-x)Ix(x=0~1)超薄异质纳米结构，采用开尔文探针力显微镜测试表面势差技术研究二维负载型超薄异质结构表面势差的影响因素及其对光生电荷的影响作用；初步揭示二维负载型超薄异质结构增强光催化降解活性机制。本项目旨在光催化剂具有大比表面积基础上探索出抑制光生载流子复合的新途径，为研制出高性能太阳光催化剂奠定理论和实验依据。

二维超薄负载型异质光催化剂具有有效分离光生电荷的性质，由于其纵向尺寸小不能通过构建内电场来进行合理解释，其产生的作用机制却又鲜见报道。本项目采用开尔文探针力显微镜测试表面电势技术从二维超薄异质结构的横向层面进行了光生载流子的分离机理探究。. 三年来，我们完成的主要研究总结为下面三个方面的内容：.(1) 设计并制备了系列的二维超薄ZnO/BiOI(内嵌ZnO)负载型及ZnO/BiOBr(1-x)Ix（x=1, 0.1)杂化型纳米结构，对其进行了微结构与化学成分表征。.(2) 研究了所制样品的光学吸收，光生电子与空穴的分离效果与载流子相对迁移快慢。分别选择了染料与有毒有机物为主要光降解对象，对所得样品进行了太阳光和可见光的光催化降解测试及相应的循环光催化评估。.(3) 通过对样品的表面电势与光沉积测试，分析了表面电势的影响因素及表面电势差驱动光生电荷的表面流向。从二维超薄异质结构的表面势差分离光生电荷的层面，结合载流子的迁移及吸光性能揭示了二维超薄异质结构增强光催化活性机制。. 此外，我们还拓展了研究对象的范围，合成了二维超薄ZnO/Bi3.9Zn0.4V1.7O10.5面内异质结构，探究了其光生载流子的分离及其光催化活性影响因素。. 基于以上研究，我们构建了一种二维超薄ZnO基负载型与杂化型异质纳米结构的制备方法，揭示了二维超薄异质纳米结构有利于光生载流子的分离本质上是其表面势差驱动的结果，探究出表面势差受化学成分及厚度的影响，初步拟出二维超薄异质纳米结构光催化增强机制。本项目的研究为针对目标有机降解物进行设计高活性光催化剂提供理论基础和实验依据。. 研究计划执行情况良好，未出现调整和变动的情况。