层结构设计调控铋系光催化材料光生载流子分离及输运性能

Different from the previous modification on the surface and interface of Bi-based photocatalytic materials, such as morphology control, elemental doping, heterostructure construction and noble metal deposition, in this project we intend to employ the crystal-structure-design means to modulate the active (Bi2O2)2+ layer structure of the layered Bi-based photocatalytic materials so as to promote the separation and migration of photogenerated carriers, thereby improving the photocatalytic properties. Herein, the BiOIO3 and BiOI are used as research subjects, and their crystal structures are modulated via polyhedral group replacement and cation compositing, and the modified crystal structures are resolved by Rietveld refinement method. By utilizing the first principles calculations, we will systematically investigate the impact of different structrual-modification strategies on the band structure, density of states, light absorption, local charge density and effective quality of charge at the modified position of the new Bi-based photocatalysts. Combining the experimental results of surface electronic structure with the behaviors of generation, migration and transformation of photogenerated charges, we intend to disclose the mechanism on promoted photocatalytic properties of Bi-based photocatalytic materials by the layered-structural-design. Through the comparison of the photoactivity-enhancement-mechanism by different polyhedral group replacement and cation compositing means, the essential reason for different separation and transfer efficiency of photogenerated charge carriers influenced by crystal-structure-regulation will be elucidated, which could provide theoretical basis and new insights for further understanding on the crystal-structure-design of photocatalytic materials.

不同于以往对铋系光催化材料进行的形貌调控、掺杂、异质结构建和贵金属沉积等表面和界面改性，本项目拟运用晶体结构设计手段调控层状铋系光催化材料的(Bi2O2)2+活性层结构，促进其光生载流子的分离和迁移，从而提升光催化性能。以BiOIO3和BiOI为模型对象，分别通过多面体基元取代和复合阳离子结构改性手段进行结构调控，通过Rietveld结构精修解析晶体结构。利用第一性原理对改性后新型Bi系催化剂模拟计算，系统研究不同晶体结构调控手段对能带结构、态密度、光吸收、改性位置局部电荷密度和电荷有效质量等的影响；结合表面电子结构、光生电荷的产生、迁移和转化行为的实验表征结果，揭示层结构设计提高Bi系光催化材料催化性能的作用机制；比较不同种类和比例的多面体取代和复合阳离子作用机制的异同，阐明晶体结构调控光生载流子分离和传递效率差异的本质原因，为深入认识光催化材料晶体结构设计和调控提供理论基础和新见解。

低电荷分离效率是制约光催化效率最主要的障碍，过去的研究主要围绕催化剂表面电荷迁移，体相分离的问题没有得到有效解决。在材料内部构建持久驱动力提高体相电荷分离效率是促进材料光催化活性的关键。提出晶体极性与层结构调控手段作为促进电荷分离的新思路，有效解决光生电荷复合的关键问题，大幅提升了光催化活性，促进了光催化材料的发展。光催化反应是发生在催化剂表面的非均相反应，表面结构对光催化活性有重要影响。以往研究主要集中于利用单一表面改性手段促进光催化活性，对性能提高有限。提出利用多重因素耦合表面结构改性思路，协同促进电荷分离，为发展高表现光催化材料及其他表面催化反应提供重要参考。通过构建薄层/氧空位/活性晶面/异质结等多个优势共同促进电荷分离和光催化活性。发展了构建高效层状光催化材料的新策略，并在环境净化（废水处理、NO净化）和制备清洁能源（光解水制氢气，CO2还原）等方面取得系列进展。本项目取得的成果包含发表SCI论文32篇，授权中国发明专利2项。