石墨烯-Ⅱ型半导体异质结构复合光催化剂的微波合成及界面微观结构和性质研究

Semiconductor photocatalysis has attracted widespread attention in scientific community due to its potential application in environmental remediation and hydrogen production. But there are still some unsolved problems such as narrow light-response range and high recombination rate for the photoinduced electron-hole pairs in pure semiconductor photocatalysts, which reduce their photocatalytic efficiency and limit them to wide application. To overcome these difficulties, many methods have been applied to improve the photocatalytic activity of semiconductor compounds. In the present work, we propose a surface modification method to prepare graphene-based typeⅡsemiconductor heterostructured nanocomposites via microwave assisted solution method. The synthetic route and process parameters including microwave power, heating time, heating temperature, ratio of reagents and the amount of graphene oxide, etc, will be optimized by using response surface methods, and the main factors which affect the structure, adsorption capacity and photocatalytic performance of the as-prepared nanocomposites will be determined. The microscopic structural and morphology factors (eg. size, shape, chemical composition, spatial distribution, heterojunction of the grapheme-based semiconductor heterostructures) which have synergistic impacts on the photoelectrochemical properties and photocatalytic performance of photocatalysts will be systematically investigated. The mechanism for highly efficient photogenerated charge carrier separation and transport at the interface of herterstuctures will be proposed. On this basis, by using first-principles based on density functional theory (DFT) and molecular dynamics methods, the interfacial structures of the as-prepared composites and their microscopic dynamic binding processes the will be theoretically studied through model design and computational simulation. The influence of interface structures, such as species of interfacial atoms, stacking orders, dislocation, defects, doping and arrangement of boundaries on the electronic and optical properties of the composites will be explored. The cooperative effects of charge transfer induced by interfacial atomic interaction between graphene and semiconductor as well as two different semiconductors will be further confirmed by the binding energy, band structure, density of electronic state, difference charge density, and work function, etc. Thus the mechanism of photocatalytic enhancements by the composites can be elucidated. The research findings will provide an experimental and theoretical basis for design and fabrication of novel, highly efficient semiconductor photocatalysts. It is also of great significance for us to find widespread applications of the graphene-based semiconductor photocatalysts in environmental remediation.

针对半导体光催化剂的性能缺陷，本项目拟采用微波辅助溶液法制备石墨烯-Ⅱ型半导体异质结构复合光催化剂。系统研究合成路线及各工艺参数对复合材料微观结构、吸附性能和光催化性能的影响，确定主要控制因素和工艺条件。探讨复合材料表面形貌、尺寸、化学组成、空间分布、异质界面微观结构等与材料光电性能和光催化活性的内在联系，初步明确光诱导电子空穴对的转移路径和分离机制。在此基础上，采用第一性原理和分子动力学方法对复合材料界面微观结构及其动态结合过程进行模拟计算，研究界面原子类型、堆积顺序、错位、缺陷、掺杂、边界排布等微观结构变化对材料电子结构和光学性质的影响，通过界面结合能、能带结构、电子态密度、差分电荷密度、功函数等进一步明确界面原子相互作用和电子转移的协同机制，揭示复合材料光催化性能增强的机理。研究成果将为新型半导体光催化剂的设计和构筑提供实验和理论依据，同时对环境的综合治理具有重要意义。

开发可见光响应、窄带隙、高催化效率的新型光催化剂是目前环境治理领域的研究热点。本项目以典型的金属氧化物和硫化物半导体光催化剂为基础，围绕定向设计、可控合成、晶面控制、核壳包裹及多维结构构筑开展了一系列以石墨烯和纤维碳为基底的异质复合光催化材料的研发与应用，主要研究内容为：（1）微波辅助溶剂热法合成暴露TiO2高能{001}晶面的RGO/TiO2和RGO/TiO2/CdS复合光催化剂及其可见光催化性能；（2）石墨烯-Bi系分级结构RGO/Bi2WO6/Bi2MoO6、RGO/Bi2WO6/Bi2S3、RGO/Bi2WO6/Bi和Bi2S3/CdS异质光催化剂的合成、光催化性能及机理；（3）纤维素模板ZnO微/纳结构、纤维碳基ZnO/CdS异质光催化剂的微波固相合成与光催化性能。所合成的复合材料在光催化降解亚甲基蓝、罗丹明B、还原重金属离子Cr(VI)等方面都表现出了增强的可见光催化活性。同时通过催化动力学研究、活性物种捕捉研究、结合形貌表征、光学和电子性质分析等，对光催化降解有机物和重金属离子反应过程开展了机理研究，分析材料表面光生载流子在半导体和石墨烯之间的转移路径和分离效率，提出形成S型异质结构及石墨烯对电子的存储和转移是促进光生载流子有效分离，增强材料光催化活性的主要原因。在此基础上，通过第一性原理密度泛函理论对多相催化体系的表界面结构、界面相互作用和电子结构性质（能带结构、功函数、带边位置、态密度等）开展了研究，明确了光生载流子输运和转移行为，从分子和原子水平揭示纳米复合催化材料的结构-催化性能间的本质联系。本项目为新型复合光催化材料的研制提供了一定的理论依据，有望获得具有工业化应用前景的产品，为工业废水等环境污染的治理开拓新的途径。共发表论文9篇，其中SCI期刊收录6篇，EI期刊收录3篇，待发表论文5篇，申请发明专利4件，培养了7名硕士研究生。