Réocreux Romain, Kress Paul L, Hannagan Ryan T, Çınar Volkan, Stamatakis Michail, Sykes E Charles H
Thomas Young Centre and Department of Chemical Engineering, University College London, Roberts Building, Torrington Place, London WC1E 7JE, United Kingdom.
Department of Chemistry, Tufts University, 62 Talbot Avenue, Medford 02155, Massachusetts, United States.
J Phys Chem Lett. 2020 Oct 15;11(20):8751-8757. doi: 10.1021/acs.jpclett.0c02455. Epub 2020 Sep 30.
The conversions of surface-bound alkyl groups to alkanes and alkenes are important steps in many heterogeneously catalyzed reactions. On the one hand, while Pt is ubiquitous in industry because of its high activity toward C-H activation, many Pt-based catalysts tend to overbind reactive intermediates, which leads to deactivation by carbon deposition and coke formation. On the other hand, Cu binds intermediates more weakly than Pt, but activation barriers tend to be higher on Cu. We examine the reactivity of ethyl, the simplest alkyl group that can undergo hydrogenation and dehydrogenation via β-elimination, and show that isolated Pt atoms in Cu enable low-temperature hydrogenation of ethyl, unseen on Cu, while avoiding the decomposition pathways on pure Pt that lead to coking. Furthermore, we confirm the predictions of our theoretical model and experimentally demonstrate that the selectivity of ethyl (de)hydrogenation can be controlled by changing the surface coverage of hydrogen.
表面结合的烷基向烷烃和烯烃的转化是许多多相催化反应中的重要步骤。一方面，由于铂对C-H活化具有高活性，在工业中无处不在，但许多铂基催化剂往往会过度结合反应性中间体，这会导致因碳沉积和焦炭形成而失活。另一方面，铜与中间体的结合比铂弱，但在铜上的活化能垒往往更高。我们研究了乙基（可以通过β-消除进行氢化和脱氢的最简单烷基）的反应活性，结果表明，铜中的孤立铂原子能够实现乙基的低温氢化，这在铜上是看不到的，同时避免了纯铂上导致结焦的分解途径。此外，我们证实了理论模型的预测，并通过实验证明，可以通过改变氢的表面覆盖率来控制乙基（脱）氢化的选择性。
