高效还原二氧化碳的p区金属基二维纳米片材料的设计合成及光催化转化机制研究

In view of the poor reactive activity of CO2 molecules and the unclear photocatalytic mechanism, this proposal will study on the photocatalytic reduction of CO2 over novel 2D nanosheet materials. Due to the fact that the surface feature of alkaline 2D nanosheets could facilitate the chemical adsorption and activation of CO2 molecules, a series of p-block metal-based 2D nanosheets with strong surface Lewis basicity will be synthesized. The surface defects and microstructures of the as-prepared 2D nanosheets will be regulated by the surface treatment and the modification of the alkaline cocatalysts. The adsorption and activation of CO2 molecules over the surface of 2D nanosheets will be investigated to establish the interaction relationship between CO2 molecules and the surface of 2D nanosheets. The catalytic conversion ratio and selectivity of the 2D nanosheet photocatalysts will also be determined. Furthermore, the effects of the component, structure, and surface state of 2D nanosheets on their photocatalytic activities and stabilities will be clarified. And then, the novel and highly efficient 2D nanosheet photocatalysts will be developed. In addition, the possible intermediates during the reaction process will be detected and the dissociation and transformation of CO2 molecules on the surface of the photocatalysts will be revealed. Finally, a probable photocatalytic reduction mechanism of CO2 over p-block metal-based 2D nanosheets will be proposed. This study is expected to have significant academic value not only in guiding the design of novel and high efficient photocatalysts for the reduction of CO2, but also providing a new insight in comprehensively understanding the nature of photocatalytic reduction of CO2 at the molecular level.

针对CO2分子在光催化转化中反应活性低和催化转化机制不明确等问题，本项目拟开展新型二维纳米片材料光催化还原CO2的研究。基于碱性二维纳米片的表面效应有利于CO2的化学吸附和活化，设计制备系列表面Lewis碱性较强的p区金属基二维纳米片，通过表面处理和碱性助催化剂修饰，调节二维纳米片材料的表面缺陷和微观结构。研究CO2在二维纳米片表面的吸附-活化状态，揭示CO2分子与二维纳米片表面的相互作用；考察这些光催化材料的催化转化率和选择性，探明材料的组成-结构-表面态等对其光催化活性和稳定性的影响，开发出还原CO2性能优异的光催化材料；探寻CO2分子在催化转化过程中的可能中间产物，阐明CO2分子在催化剂表面的解离和催化转化过程，提出光催化转化CO2机制。该研究探索不仅对指导新型高效光催化还原CO2的材料设计开发具有重大理论研究价值，而且对从分子水平上深入理解光催化转化CO2机制具有重要意义。

利用光催化技术实现CO2的有效转化是光催化和环境化学领域的研究热点。但是目前光催化还原CO2体系的效率仍然较低，其难点在于CO2分子的吸附活化及催化转化过程。本项目开发了系列铌基、钛基、锡基、氮化碳复合材料等共16种二维纳米片光催化剂。这些二维纳米片材料在CO2还原、光解水和有机物选择性转化方面表现出了优异的性能和催化活性稳定性。同时为了提升其光催化活性，进一步利用过渡金属、贵金属和半导体修饰等方法来构建复合材料。研究了二维纳米片制备条件对于材料质量的影响，探讨了这一系列材料的组成、结构、表面态等对光催化性能的影响。利用分子光谱和原位表征手段，揭示了这些材料光催化反应过程本质。通过原位红外实验揭示了光催化还原CO2为CO的反应体系中，起主要作用的活性物种为表面吸附活化的CO2-，吸附的H2O起到提供质子的作用。助催化剂的引入改变了纳米片催化剂的表面性质，有效促进电子空穴的分离，并提高复合材料的光催化活性。这些研究成果将对超薄二维纳米片光催化剂的制备、结构调控以及分子水平上认识光催化作用提供重要的学术性指导作用，有效推动了光催化领域的发展。