原子层沉积设计空间分离催化剂及其氢溢流效应的XAFS研究

As a widespread phenomenon in catalysis, spillover has attracted much attention. It is of great significance to study the hydrogen spillover process for revealing the catalytic mechanism and designing and constructing new catalysts. However, due to the limitations of traditional preparation and characterization methods, the lack of accurate model catalysts and efficient in-situ characterization techniques have hindered the establishment of structure-performance relationships, and its importance in the catalytic reaction remains controversial. In this project, precise and controllable bimetallic model catalytic system with spatially separated structures will be constructed by atomic layer deposition, and the dynamic process of the local electronic and geometrical structures of catalytic nanoparticles under real reaction conditions will be tracked by synchrotron radiation XAFS. The influence of bimetallic composition, spillover condition, surface/interface structure and the distance between bimetallic nanoparticles on the hydrogen spillover effects will be studied, and the relationships between the catalyst microstructure and the hydrogen spillover effects will be resolved. The hydrogenation of cinnamaldehyde and the hydrogen generation from hydrolysis of ammonia borane will be carried out to study the impact of hydrogen spillover effects on the catalytic performances. Furthermore, hydrogen spillover will be introduced into the epoxidation reaction to explore the effect of hydrogen flux on the electronic state of the active sites and their epoxidation performance. These studies will reveal the essence of the spillover effects, further deepen the theory of the effects, and provide scientific evidence for the design of new efficient catalysts.

溢流作为催化中广泛存在的现象，一直备受关注。研究氢溢流过程对揭示催化机理，设计新型催化剂都有重要意义。然而，受传统制备方法、表征手段的限制，缺乏精准的催化剂模型以及高效的原位动态表征技术，阻碍了构效关系的建立，氢溢流在反应中的重要性尚存争论。本项目拟采用原子层沉积构建精准可控的空间分离双金属模型催化体系，利用同步辐射XAFS跟踪催化剂纳米粒子的局域原子结构及电子结构等在真实反应条件下的动态变化过程。研究双金属组分、溢流环境、表界面结构、双金属粒子间距等对氢溢流效应的影响规律，解析催化剂微结构与氢溢流效应之间的构效关系。以催化肉桂醛加氢和氨硼烷产氢为探针反应，研究氢溢流效应影响催化反应性能的内在机制。进一步将氢溢流引入到环氧化反应中，探究氢物种通量对催化活性位点的电子状态以及环氧化反应性能的影响规律。通过以上研究，揭示溢流效应的物理化学本质，深化其催化理论，为设计新型高效催化剂提供科学依据。

溢流作为催化中广泛存在的现象，一直备受关注。研究氢溢流过程对揭示催化机理，设计新型催化剂都有重要意义。然而，受传统制备方法、表征手段的限制，缺乏精准的催化剂模型以及高效的原位动态表征技术，阻碍了构效关系的建立，氢溢流在反应中的重要性尚存争论。本项目采用原子层沉积构建了精准可控的空间分离双金属模型催化体系，利用同步辐射XAFS跟踪催化剂纳米粒子的局域原子结构及电子结构等在真实反应条件下的动态变化过程。构建出NiO/Al2O3/Pt空间分离催化体系，研究催化剂对于氨硼烷产氢反应的催化性能，同时利用XAFS对ALD构建的催化剂进行催化反应条件下的原位动态表征，提出了氨硼烷产氢反应中的反溢流协同促进过程。在此基础上，构建了CoOx/Al2O3/Pt空间分离催化剂，利用氢溢流原位精准调控催化活性中心电子结构，原位XAFS表明反应体系中引入可控氢溢流使得反应中钴物种处于更低的价态，从而显著提高了催化剂对于环氧化反应的选择性。我们还提出一种有机分子修饰载体策略，通过在不可还原性载体上脉冲修饰有机分子，大幅提高氢溢流强度，且可通过改变脉冲次数精准调控氢溢流强度，进而提升催化剂对于肉桂醛加氢反应的活性。此外，构建了富氧空位的Pt-Ov界面结构，以及利用臭氧脉冲策略对催化剂表面浸润性进行精准调控，提升了对硝基氯苄选择性加氢、对硝基苯酚加氢等反应的催化性能。最后，系统综述了近年来多相催化中溢流的相关研究进展，对目前存在的难题和未来的发展方向进行了展望。