超细双金属纳米催化剂反应条件下动态结构转变的原位同步辐射研究

超细双金属纳米颗粒是一类具有重要应用前景的新型催化剂，但它们在催化反应过程中容易发生颗粒聚集或结构变化，从而影响催化活性和稳定性。揭示它们在催化反应过程中的真实微观结构和协同效应对理解其催化现象和本质至关重要。本项目拟通过多种液相反应和金属-载体相互作用的方式，设计合成对重要的氧化或加氢反应具有优异催化性能的负载型Pt-M（M=Fe、Co、Ni）超细双金属催化剂。利用原位变温同步辐射XAFS和DRIFTS技术，追踪研究在催化反应过程中该催化剂的双金属成分可能发生的表面偏析、合金化、氧化还原等变化过程，获得有关颗粒尺寸、化学组成、配位形式和电子结构等的动态信息，以及反应中间物的形成和转化途径。再结合密度泛函理论对表面吸附自由能的计算与过渡态搜索，以及催化反应动力学测试等，明确活性中心的特征，揭示双金属成分间的几何和电子协同作用机理，为合理设计构筑新型双金属纳米催化剂提供有益借鉴。

Ultrafine bimetallic nanoparticles are a category of novel catalysts with promising applications, but they are prone to particle agglomeration and structure transformations because of their large surface energy and high mobility of atoms therein. Therefore, uncovering the real microscopic structures and synergetic effects in ultrafine bimetallic nanoparticles under reaction conditions is of critical importance for understanding the origin of their catalytic performances. In this project, we are going to synthesize via wet chemistry methods various supported ultrafine Pt-M (M=Fe, Co, Ni) nano-catalysts that are highly active for selected oxidation and/or hydrogenation reactions. Temperature-dependent in situ XAFS and DRIFTS characterizations will be combined to track the dynamic structure evolutions, including changes in particle size, surface segregation, alloying/dealloying, oxidation/reduction, of these supported bimetallic catalysts under real catalytic conditions, as well as to monitor the creation and transformation of reaction intermediates. DFT calculations of the potential energy surface and transition states combined with catalytic kinetics measurements will help to determine the atomic/electronic structures of active sites, to enrich our understanding on the synergistically geometric or electronic effects of the bimetallic components. This project could provide valuable hints for rational design and precise construction of novel bimetallic catalysts.