碱性增强铋系复合氧化物高效光催化还原CO2制备碳氢燃料研究

At present, the lack of efficient visible light-driven photocatalyst, and the unclarified mechanism seriously limit the application of CO2 photoreduction. It was found that the photoreduction of carbonates into hydrocarbons is easier than that of CO2. Based on this, we will synthesize basic metal oxide-enhanced Bi-based composite, which could: 1) enhance the basic property on catalyst surface, then increase the amount of carbonates; 2) fabricate heterostructure between basic metal oxide and Bi-containing complex oxide (such as Bi2WO6, Bi2MoO6, etc.), then promote the separation of photogenerated electron-hole pairs. Furthermore, the relationship among the composition, structure and activity of photocatalyst, as well as the mode of CO2 chemical adsorption and activation will be investigated in detail. At the same time, the project will also focus on to explore the activation mechanism of C=O bond, and determine the rate-determining step during the CO2 photoredcution process, which will benefit the discovery of reaction mechanism. This study will provide important evidences for the further development of photocatalysts and effective strategy to solve the problems of energy and environment in the future.

目前可见光响应催化剂的缺乏、光还原机理不明确等难题严重制约了CO2光催化还原的发展应用。我们根据CO2可通过转化为碳酸盐物种进而更易被光还原为碳氢燃料这一发现，拟构建碱性金属氧化物与铋系多元氧化物复合的新型光催化材料。在基于Bi系多元氧化物具有较好可见光催化活性的同时利用碱性金属氧化物：1）引入碱性位增强其表面CO2化学吸附能力，进而提高碳酸盐物种浓度，促进反应的进行；2）与Bi2WO6、Bi2MoO6等铋系多元氧化物耦合构建异质结，加速光生电子-空穴分离，提高光催化活性。同时，系统研究催化剂的组成-结构-活性之间的关系，明确光催化反应过程中CO2分子吸附活化方式及相关物种的光催化反应途径，阐明C=O键活化机理并确定光催化反应速率限制步骤，揭示光催化反应机理。本项目的成功实施，有望获得CO2光还原高效催化剂，为同时解决温室效应和能源危机提供完美解决方案。

该项目研究工作以温室气体CO2的低能耗、高效率光催化还原加氢能源化为应用目标，针对CO2加氢转化过程中的理论难点与技术发展，构建一系列具有强吸附力、富电子界面、高催化活性的碱性铋系异质结催化剂：如CeO2/Bi2MoO6、Ag/Ag3PO4/CeO2、CeO2/Ti3C2TX，阐明具有多空d轨道的CeO2是提高碳酸盐类活性物种b-CO32−和b-HCO3−转换的关键影响因素；构建多维超薄Bi2MoO6纳米片、低维Bi2MoO6量子点敏化石墨烯、WS2内嵌Bi2S3纳米管等催化体系，明确具有缺陷空位的催化界面局域电子重排、催化剂内部能带重构是提升光电催化活性、增大还原电子流密度，降低CO2活化能垒的首要前提。此外，为增强催化剂对CO2的吸附容纳，提高反应几率，将具有超大比表面积的MOF功能基底引入CO2的催化还原并取得了较好的预期效果。通过本项目研究，揭示了光催化剂与CO2高值转化效率直接的作用关系，厘清了CO2在催化界面的吸附-活化-加氢过程中的分子热力学、动力学过程，阐明了光催化还原CO2的本质原理。本研究工作为光催化技术在CO2能源转化应用中的低能耗输入、高效率转化、温室气体高值转化技术及相关拓展研究提供理论技术与数据借鉴。