高指数面纳米晶的合成及其可见光光还原二氧化碳的研究

Global energy crisis and greenhouse effect caused by carbon dioxide are two of the major issues concerning sustainable development of humanity. Photocatalytic reduction of CO2 to valuable hydrocarbons is one of the best solutions to both the global warming and the energy shortage problems. In this project, we regard the semiconducting systems of visible-light-responsive transition metal oxides as the main research object, and study their visible-light-driven photocatalytic reduction of CO2. This project mainly studies the controllable synthesis of transition metal oxide nanocrystals with high-index facets and visible light photoreduction of CO2 into hydrocarbons. This research project also conducts in-depth theoretical calculations to design the new material systems with visible-light-responsive photocatalytic reduction of CO2. In addition, synchrotron radiation XAFS and XPS are performed to investigate the structural variations such as bond length, bond angle and valence states of photocatalysts during the photoreduction of CO2 under the visible-light irradiation, in efforts to achieve the correlation between structural variation and photoreduction of CO2; meanwhile, the corresponding calculations further help to obtain theoretical understanding on the underlying correlation between synthesis, structure and property, thus offering a theoretical basis to improve the photoreduction efficiency of CO2 into hydrocarbons. Therefore, this project will realize the controllable synthesis of transition metal oxide nanocrystals with high-index facets, and fabricate high-performance photocatalytic materials for converting CO2 into hydrocarbons.

全球性能源短缺和CO2排放引起的温室效应是影响人类可持续发展的两个重大问题。光催化还原CO2成有机燃料分子是解决全球变暖和能源短缺的有效途径之一。本项目将以能够吸收可见光的过渡金属氧化物半导体体系为主要研究对象，聚焦光还原CO2的应用，以过渡金属氧化物高指数面纳米晶的可控合成和可见光光还原CO2的性能测试为研究主线，深入开展从分子层次到结构单元层次下可见光光还原CO2材料的理论模拟与化合物设计，利用同步辐射XAFS和XPS等对材料在光还原CO2反应中晶体结构的键长、键角和价态等方面的变化进行深入研究，从而了解这些变化对其光还原性能的具体影响；经过理论计算，将对高性能光催化材料的合成-结构-性能三者之间的关系形成一些本质的理论认识，进而为提高光还原CO2的效率提供一种理论基础。通过该项目的实施，将实现具有高指数晶面的过渡金属氧化物纳米晶的可控制备，并且研制出高性能的可见光光还原CO2的材料。

在本项目的实施中，我们从特征晶体结构出发，发展出系列直接液相剥离法，实现了层状化合物类石墨烯单层结构的可控制备；创新性地提出了普适的合成非层状化合物类石墨烯结构的方法，实现了非层状化合物超薄二维结构的可控制备；针对非层状化合物无法直接剥离的困难，提出了系列制备非层状化合物类石墨烯结构的bottom-up合成策略；利用同步辐射XAFS技术解析了这些低维超薄材料的精细结构并首次揭示出表面扭曲的存在能够使得原子级厚的非层状化合物更加稳定的存在；理论计算揭示出其态密度在费米面附件有明显增强，这无疑有利于其获得更高的载流子迁移率，进而提高其光电催化性能；因此，通过本项目的实施，对高性能光电催化材料的合成-结构-性能三者之间的关系形成一些本质的理论认识，进而为提高光电还原CO2的效率提供一种理论基础。以上有关工作超额完成项目任务书的研究内容，共在1篇Nature，1篇Nature Communications，2篇Chem. Soc. Rev., 1篇Acc. Chem. Res., 2篇J. Am. Chem. Soc, 5篇Angew. Chem. Int. Ed.，1篇Adv. Energy Mater., 1篇Nano Energy, 1篇Chem. Sci.等国际顶级刊物上发表16篇论文。3次被Nature Index报道，相关工作入选中国科学院重大科学基础设施重大成果。