双金属表界面烃类小分子化学转化的机理研究

Bimetallic catalysts play an essential role in the dehydrogenation of light alkanes. However, due to its great complexity, the molecular mechanisms of bimetallic catalysis are still far from being fully understood. In this project, we will concentrate on bimetallic systems between Pt group and coinage metals and the direct dehydrogenation of propane to propylene is chosen as the target reaction. On one hand, we will develop more efficient modeling methods which are suitable to simulate such complex systems. On the other hand, by using the newly developed methods, combined with kinetic MC and ab initio molecular dynamics, we will be able to explore the detail mechanisms of the activation of C-H bonds, the breaking of C-C bonds, the evolution of CxHy species, and the spillover of reactant and intermediates over different kind of bimetallic model catalysts, such as single atom alloys, multi-atom alloys, solution alloy and core-shell type alloys, and provide a general descriptor to elucidate the interfacial synergy between different metals. Based on these, controlled synthesis and catalytic study of noble bimetallic nanostructures will be carried out.

双金属催化材料在催化烷烃脱氢中发挥着重要的作用。由于双金属结构的复杂性，其界面协同的分子机制目前尚未阐明。本项目将紧密结合能源领域的需求，以丙烷无氧脱氢制丙烯为目标反应，细致考察铂族金属和币族金属构成的双金属模型催化体系。发展新的模型方法，对比考察单(多)原子合金体系、固溶体合金体系和核壳结构合金结构。应用密度泛函为主的理论方法，结合动力学蒙特卡洛（KMC）、分子动力学（MD）和构型统计，深入探讨C-H键的活化、C-C键的断裂，CxHy在临氢条件下的演化以及不同表面物种的溢流过程，提出描述双金属表面反应的普适描述符，阐明界面协同的科学内涵。结合实验，为新型纳米催化剂的理性设计提供科学依据。

多相催化通常涉及复杂的表界面，导致合理的模型构筑非常困难。在本项目中，我们建立了一套模型构建原则，即“实验作减法，理论作加法”。结合实验，我们将阐明影响催化选择性的分子因素，特别是针对重要的铜基催化剂。系统的理论研究将有助于深入认识选择加氢和选择氧化的关键问题：(i)钯到铜的氢溢出是晶面依赖的的，溢流加氢只发生在Pd1/Cu(100)上，其中钯溢出的氢原子很容易用于炔烃的半氢化；(ii)Cl修饰的Cu(I)促进亲电氧的形成；有利于丙烯的直接环氧化(iii)理论计算明确了Cu(110)表面钝化层的原子结构被确定为双核[Cu(μ-HCOO)(OH)2]2单元和O2− 以c(6×2)配置排列。