钴基二元金属团簇吸附乙炔基的理论研究

The adsorption of small molecules on metal clusters is of considerable interest both in chemical and industrial applications, primarily due to its key effect in many catalytic processes that are closely related to national economy as well as environmental improvement. Compared with monometallic catalysts, bimetallic catalysts usually display the unique and superior catalytic performance. The ethynyl radical is known to be a key intermediate in the combustion of hydrocarbon which will be also prone to be formed during acetylene catalyzed by metals. In this project, the quantum chemical calculations will be carried out to study the adsorption of ethynyl on cobalt-based bimetallic MCon (M = Al, Sc, Cr, Mn, Cu; n = 1–5) clusters. The study will focus on the structural stabilities and special properties of neutral/anionic cobalt-based bimetallic clusters adsorbing ethynyl. Based on our investigations, geometric, size and composition effects of cobalt-based bimetallic clusters adsorbing ethynyl will be discovered. The geometric and electronic structures, electron binding energies and adsorption energies of MConC2H (M = Al, Sc, Cr, Mn, Cu; n = 1–5) will be obtained. Furthermore, the study will shed light on the structural and magnetic influences of the adsorbate ethynyl to cobalt-based bimetallic clusters. Therefore, our study will provide insight into understanding the related catalytic mechanism at the molecular level and improving or designing the bimetallic catalysts as well as novel magnetic materials.

金属团簇对小分子的吸附在催化过程中具有关键作用，涉及到一些与国民经济、环境治理等密切相关的工业过程，有关它们的研究受到了广泛关注。和纯金属催化剂相比，二元金属催化剂往往具有独特且优异的催化性能。乙炔基是烃类燃烧过程中的一个重要中间体，是乙炔在金属催化剂上易形成的中间体。本项目拟采用量子化学计算方法开展钴基二元金属团簇MCon (M = Al, Sc, Cr, Mn, Cu; n = 1–5)吸附乙炔基(C2H)的研究。我们将着重从中性和带负电荷的钴基二元金属团簇吸附乙炔基的结构稳定性和特性去研究，以揭示钴基二元金属团簇吸附乙炔基的结构效应、尺寸效应、组成效应；预测钴基二元金属团簇吸附乙炔基形成团簇的几何和电子结构、电子结合能、吸附能等信息；同时，这些研究还能帮助认识乙炔基对钴基二元金属团簇结构和磁性的影响，从而为相应催化反应的微观机理及改进或设计二元金属催化剂和新型磁性材料提供理论基础。

乙炔基(C2H)是CVD方法制备石墨烯、碳纳米管等碳材料的一个中间体，也是金属催化烃类反应的一个重要中间体。相对于贵金属，金属钴具有储量丰富、价格实惠的优势，而二元金属催化剂具有独特且优异的催化性能。本项目在基金委青年项目的资助下，应用密度泛函理论计算方法，研究了钴基二元金属团簇AlCon、ScCon对C2H的吸附，以及Cu掺杂Co(111)表面对C2H的吸附、催化加氢和去氢反应机理。团簇研究结果表明：Al、Sc取代Co几乎不影响Con团簇的几何结构，Al、Sc主要通过共价键与Co相互作用。C2H主要通过其π轨道与Co的3d轨道相互作用成键；随着团簇尺寸的增大，C2H逐渐远离Al和Sc，更易吸附在Co团簇上。此外，我们预测了AlCon、ScCon及其吸附乙炔基形成团簇的绝热和垂直电子脱附能，为这些实验上难以制备的团簇提供了物理参数的参考。表面研究结果表明：多个Cu掺杂的表面，Cu更易聚集在表面；Cu的引入调节了Co表面对乙炔基的吸附，进而调节了乙炔基加氢和去氢的反应能垒；另外，我们发现：氢的浓度影响乙炔基在Cu/Co(111)表面的吸附方式。我们的研究结果为碳材料的生长机理及烃类反应的催化机理提供了基础信息和帮助。