Nanoalloying MgO-Deposited Pt Clusters with Si To Control the Selectivity of Alkane Dehydrogenation,ACS Catalysis

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Nanoalloying MgO-Deposited Pt Clusters with Si To Control the Selectivity of Alkane Dehydrogenation
ACS Catalysis ( IF 11.3 ) Pub Date : 2018-07-24 00:00:00 , DOI: 10.1021/acscatal.8b02443
Elisa Jimenez-Izal _{1,

2} , Huanchen Zhai ₁ , Ji-Yuan Liu ₁ , Anastassia N. Alexandrova _{1,

3}

Affiliation

Nanoalloying MgO-deposited Pt clusters with eight main-group elements was computationally screened for potential selectivity toward partial dehydrogenation of small alkanes. Si was revealed as a promising dopant for Pt across two cluster sizes, as it appears to favor stopping dehydrogenation of alkanes at alkenes. Pure Pt clusters on MgO(100) tend to strongly adsorb ethane and activate one of the C–H bonds but then bind ethylene in an activated di-σ fashion and even spontaneously dehydrogenate it. They also strongly bind C atoms, as the first step of deactivation by coking. PtSi clusters also bind and activate ethane but, in contrast to pure Pt clusters, bind ethylene preferentially in a weaker π fashion and do not spontaneously dehydrogenate it. Additionally, the affinity of C atoms to PtSi is reduced by ca. 2 eV in comparison to pure Pt clusters of the same size. Finally, Si stabilizes the clusters against dissociating single Pt atoms and thus is predicted to slow down catalyst sintering by Ostwald ripening. Thus, Si is predicted to improve both the selectivity and stability of Pt cluster catalysts. The cluster behavior appears to be linked to its spin multiplicity: isomers with unpaired electrons exhibit high activity and, while they are abundant for pure Pt clusters, Si tends to quench spins. Si also causes clusters to become more globular, with fewer valence-unsaturated Pt sites. The discovered properties of Si potentially exceed those of B, the recently proposed doping agent for Pt clusters whose effect on selectivity was confirmed experimentally.

中文翻译：

用Si纳米化MgO沉积的Pt团簇以控制烷烃脱氢的选择性

通过计算筛选了具有8个主族元素的纳米MgO沉积Pt团簇，以了解小烷烃部分脱氢的潜在选择性。硅被认为是跨越两个簇尺寸的有希望的Pt掺杂剂，因为它似乎有利于阻止烯烃的烷烃脱氢。MgO（100）上的纯Pt簇倾向于强烈吸附乙烷并激活C–H键之一，但随后以活化的di-σ方式结合乙烯，甚至自发地将其脱氢。它们也牢固地结合C原子，这是通过焦化使其失活的第一步。PtSi团簇还结合并活化乙烷，但是与纯Pt团簇相反，PtSi团簇优先以较弱的π方式结合乙烯，并且不会自发地将其脱氢。此外，C原子对PtSi的亲和力降低了约5％。与相同大小的纯Pt簇相比为2 eV。最后，Si稳定了团簇以防止离解单个Pt原子，因此可以预测，通过奥斯特瓦尔德（Ostwald）熟化会减慢催化剂的烧结速度。因此，据预测，Si将改善Pt簇催化剂的选择性和稳定性。团簇的行为似乎与其自旋多重性有关：具有不成对电子的异构体表现出高活性，尽管它们对于纯Pt团簇而言很丰富，但Si倾向于淬灭自旋。Si还使簇变得更球形，具有更少的价不饱和Pt位点。Si的发现特性可能会超过B，后者是最近提出的Pt团簇掺杂剂，其对选择性的影响已通过实验得到证实。Si使团簇稳定以免离解单个的Pt原子，因此据预测会因Ostwald熟化而减慢催化剂的烧结。因此，预计Si将改善Pt簇催化剂的选择性和稳定性。团簇的行为似乎与其自旋多重性有关：具有不成对电子的异构体表现出高活性，尽管它们对于纯Pt团簇而言很丰富，但Si倾向于淬灭自旋。Si还使簇变得更球形，具有更少的价不饱和Pt位点。Si的发现特性可能会超过B，后者是最近提出的Pt团簇掺杂剂，其对选择性的影响已通过实验得到证实。Si使团簇稳定以免离解单个的Pt原子，因此据预测会因Ostwald熟化而减慢催化剂的烧结。因此，预计Si将改善Pt簇催化剂的选择性和稳定性。团簇的行为似乎与其自旋多重性有关：具有不成对电子的异构体表现出高活性，尽管它们对于纯Pt团簇而言很丰富，但Si倾向于淬灭自旋。Si还导致簇变得更球形，具有更少的价不饱和Pt位点。Si的发现特性可能会超过B，后者是最近提出的Pt团簇掺杂剂，其对选择性的影响已通过实验得到证实。团簇的行为似乎与其自旋多重性有关：具有不成对电子的异构体表现出高活性，尽管它们对于纯Pt团簇而言很丰富，但Si倾向于淬灭自旋。Si还使簇变得更球形，具有更少的价不饱和Pt位点。Si的发现特性可能会超过B，后者是最近提出的Pt团簇掺杂剂，其对选择性的影响已通过实验得到证实。团簇的行为似乎与其自旋多重性有关：具有不成对电子的异构体表现出高活性，尽管它们对于纯Pt团簇而言很丰富，但Si倾向于淬灭自旋。Si还使簇变得更球形，具有更少的价不饱和Pt位点。Si的发现特性可能会超过B，后者是最近提出的Pt团簇掺杂剂，其对选择性的影响已通过实验得到证实。

更新日期：2018-07-24

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