近常压光电子能谱对PdAg界面上CO加氢反应的原位表征研究

Study on the reaction mechanism is the foundation of all R & D work. However, the solid evidence for the mechanism of CO hydrogenation is still scarce and it has not been a consensus so far due to the by-products for the reaction is numerous and complicated. Literature and our previous work showed that atomic H in either of bulk or surface of catalyst may have a different impact on CO absorption state, reaction rate, activation energy and product distribution. This project will employ PdAg alloy membranes as model catalyst. Combined with a H atom concentration control device, a manipulative component of domestic the first in situ ambient pressure x-ray photoelectron spectroscope will be designed and modified to enable concentration of H atom in both of metal bulk and surface control accurately. In combination with other advanced characterization techniques, we will in situ investigate the reaction mechanism of hydrogenation of CO in atmospheres of molecular hydrogen, atomic hydrogen and PdAgH phase with different extent of lattice expansion on PdAg alloy membranes surfaces, and also study the effect of metal segregation caused catalyst degeneration on catalytic process. This investigation will provide a beneficial theoretical support to the reaction mechanism of CO hydrogenation and also provide an innovative approach to study catalytic reaction mechanism and solid/gas interfaces interaction.

反应机理的研究是一切研发工作的基础。CO加氢反应的产物庞杂，副反应多，人们对其反应机理的了解还不够全面。文献和我们以往的研究工作表明，反应中催化剂表面或体相中不同的氢原子浓度可能会对CO的吸附态、反应速率、活化能及产物分布产生影响。本课题以PdAg膜作为模型催化剂，采用氢原子浓度控制装置，并通过改造国内首台近常压光电子能谱仪，精确控制金属体相及表面中氢原子的浓度，结合其他先进表征技术，原位研究CO与氢原子、氢分子及不同金属-氢相的反应机理，并对反应过程中金属偏析引起的催化剂变性进行研究。这些研究可为CO加氢反应机理提供理论支持，并为催化反应机理及气固界面相互作用提供一种新颖的研究方式和思路。

通过研究CO在钯膜表面吸附，发现CO的引入不能使钯膜表面钯状态发生改变，随后通入氧气，观察到亚表层氧化物的形成。CO加氢反应过程中，反应池已经设计出来，但由于反应池和近常压光电子谱仪配合使用过程中密封性不能满足要求，没能按计划进行下一步实验。通过校准残余气体分析仪和腔体压力的关系，实现对反应过程中的产物进行精准分析。