抗结焦亚纳米脱氢催化剂：Pt $_n$ Sn $_x$ / SiO $_2$（n = 4，7）
Coking-Resistant Sub-Nano Dehydrogenation Catalysts: Pt$_n$Sn$_x$/SiO$_2$ (n = 4, 7)
摘要：
以乙烯中间体为模型反应物，对Pt $_n$ /$_2$和Pt $_n$ Sn $_x$ /$_2$（n = 4，7）模型催化剂进行了吸热脱氢的实验和理论研究.支持纯Ptn集群被发现是高度活跃的C2 D4的脱氢，迅速失活，由于碳沉积和烧结的组合，导致可访问的Pt站点的损失。此外，Sn的Ptn簇的结果在C2 D4脱氢和碳沉积的完全抑制，也稳定了集群对热烧结。理论表明，这两个系统都有大量的集群结构和吸附质的配置，形成一个统计合奏热访问。虽然Pt 4/SiO2簇以二σ和π键合构型结合乙烯，但Pt $_4$ Sn $_3$ /SiO $_2$仅以π模式结合C2 H4，其中二σ键合被PtSn簇的电子和几何特征的组合抑制。采用爬像轻推弹性带（CI-NEB）方法计算了可及簇合物异构体的脱氢反应曲线。
英文摘要：
We present a combined experimental/theoretical study of Pt$_n$/SiO$_2$ and Pt$_n$Sn$_x$/SiO$_2$ (n = 4, 7) model catalysts for the endothermic dehydrogenation of hydrocarbons, using the ethylene intermediate as a model reactant. Supported pure Ptn clusters are found to be highly active toward dehydrogenation of C2D4, quickly deactivating due to a combination of carbon deposition and sintering, resulting in loss of accessible Pt sites. Addition of Sn to Ptn clusters results in the complete suppression of C2D4 dehydrogenation and carbon deposition, and also stabilizes the clusters against thermal sintering. Theory shows that both systems have thermal access to a multitude of cluster structures and adsorbate configurations that form a statistical ensemble. While Pt4/SiO2 clusters bind ethylene in both di-sigma and pi-bonded configurations, Pt$_4$Sn$_3$/SiO$_2$ binds C2H4 only in the pi-mode, with di-sigma bonding suppressed by a combination of electronic and geometric features of the PtSn clusters. Dehydrogenation reaction profiles on the accessible cluster isomers were calculated using the climbing image nudged elastic band (CI-NEB) method.
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