基于金属缺陷和氧缺陷TiO2的p-n同质结光催化剂构建及作用机理

TiO2 is an important photocatalyst in energy and environmental science. The synthesis of visible-light response and highly active TiO2 remains a challenge. N-type oxygen-defected TiO2-x is promising photocatalyst for visible light utilization, and the applicant recently synthesized metal-defected Ti1-xO2 with p-type conductivity. In this project, nanoscaled p-n homojunction will be constructed using these two materials, which is expected to have three advantages: utilizing visible light by oxygen-defected TiO2-x, improving charge separation by the junction, and enhancing stability of TiO2-x by moving away photo-induced holes. Two key scientific issues, namely controllable synthesis of nanoscaled p-n homojunction, and charge transfer mechanism of p-n junction and its optimization, will be addressed. First, to maximize the junction interface, the synthesis method will be explored to fabricate Ti1-xO2 and TiO2-x in nano-size and quantum-size, and to further decorate the surface of nanoparticles with quantum particles of another photocatalyst. Then two interface models, namely TiO2-x QDs decorated Ti1-xO2 and Ti1-xO2 QDs decorated TiO2-x, will be studied to correlate the relationship between photocatalytic performance and interface structure. Finally, to optimize the interface structure, a DFT computation will be conducted to understand the mechanism of electron transfer across the interface and the critical influence factors. This project is expected to synthesize TiO2 with high visible-light activity and high stability, to deeply understand how the junction interface works, and thus to provide new insights in rational design and fabrication of highly efficient photocatalyst.

TiO2是能源和环境化工的重要光催化剂，制备能利用可见光、催化活性高的TiO2仍是挑战。n型导电的氧缺陷型TiO2-x是极具前景的可见光催化剂，申请人近期制备了p型导电和高活性的金属缺陷型Ti1-xO2。本项目将以二者为基础，在纳米尺度构建p-n同质结，利用结界面的电荷分离来增强可见光活性和稳定性。围绕“纳米尺度p-n同质结的可控合成”和“p-n同质结界面的作用机制及匹配优化”关键科学问题，发展纳米和量子尺寸Ti1-xO2和TiO2-x制备方法，将量子点生长于纳米颗粒表面，实现结界面最大化；以两种结界面(TiO2-xQD/Ti1-xO2、Ti1-xO2QD/TiO2-x)为模型，建立界面结构与催化性能的构效关系；采用理论计算阐述结界面电荷传递机理及影响因素，实现结界面匹配优化。项目可望制备一种具有高可见光活性和高稳定性的TiO2，深入理解界面工作机制，为高效光催化剂设计和制备提供新思路。

光催化是利用太阳能驱动化学反应，进行水分解产氢、污染物脱除、合成功能化学品的重要方式，也是减少对化石能源的依赖，实现碳中和的重要途径。构筑高效光催化剂是提高光催化效率、推动光催化迈向应用的关键。本项目基于DFT理论计算和实验研究，建立了半导体催化剂金属缺陷和氧缺陷结构的可控制备方法，以及纳米尺度p-n同质结和异质结半导体的可控制备方法，阐明了缺陷结构及结界面对光催化性能的影响规律，揭示了半导体体相及跨越结界面的电荷传递机制，实现了纳米尺度p-n结的可控合成和结界面的匹配优化，为高效光催化剂的设计和制备提供了途径。主要成果如下：（1）提出金属缺陷抑制载流子（电子和空穴）复合的机制：费米面附近的电子自旋方向高度极化，传输过程中形成与空穴相反的自旋方向，从根本上抑制二者复合，近乎100%自旋极化的Ti0.936O2的催化活性比常规TiO2提高20倍；（2）阐述氧缺陷结构促进半导体活性的机制：催化剂对光的吸收，电荷转移效率及光催化水氧化活性与氧缺陷的浓度有密切关系，氧缺陷大幅度降低速控步骤的活化能，限制逆反应的；（3）构建p-n同质结TiO2和p-n同质结ZnO：p-n结界面显著促进电荷分离和传递，光催化产氢活性分别较金属缺陷（p型）和氧缺陷（n型）提高1.7和7.5，光催化MO降解活性分别提高2.3和10.8；（4）构建p-n异质结TiO2/g-C3N4：协同提高催化剂的可见光利用和电荷传递能力，光催化产氢、光催化降解MO和苯酚的活性分别为g-C3N4的5.7倍、3.6倍和1.6倍。在Nat. Comm.、Angew. Chem. Int. Ed.、Adv. Mat.、催化学报、物理化学学报等发表SCI收录论文31篇，授权美国发明专利1项、中国发明专利2项，申请中国发明专利1项。培养青年人才2名，毕业研究生6名。