Carbon Monoxide Poisoning Resistance and Structural Stability of Single Atom Alloys
Carbon Monoxide Poisoning Resistance and Structural Stability of Single Atom Alloys
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DOI：
10.1007/s11244-017-0882-1
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发表时间：
2018-05-01
影响因子：
3.6
通讯作者：
Stamatakis, Michail
中科院分区：
文献类型：
--
作者：
Darby, Matthew T.;Sykes, E. Charles H.;Stamatakis, Michail
铂族金属（PGMs）在多种非均相化学过程中充当高活性催化剂。不幸的是，它们的高活性伴随着对CO的高亲和力，因此，PGMs容易中毒。将铂族金属与对CO表现出较低亲和力的金属合金化可能是防止这种中毒的有效策略。在这项工作中，我们使用密度泛函理论来证明这一战略，专注于高稀释合金的铂族金属（Pd，Pt，Rh，Ir和Ni）与抗中毒钴金属主机（Cu，Ag，Au），使个别的PGM原子分散在原子极限形成单原子合金（SAA）。我们发现，相比于纯金属，CO表现出较低的结合强度上的大多数SAA研究，我们使用动力学蒙特卡罗模拟，以获得相关的程序升温脱附光谱，这被发现是在良好的协议与实验。此外，我们考虑了CO吸附对SAA结构的影响。我们计算的偏析能量，这是指示的掺杂剂原子的稳定性相比，在散装的表面层，以及聚集能量，以确定孤立的表面掺杂剂原子的稳定性相比，二聚体和三聚体配置。我们的计算表明，CO吸附诱导掺杂剂原子偏析到表面层的所有SAA在这里考虑，而聚集和岛的形成可能会促进或抑制，这取决于合金成分和CO覆盖。这一观察结果表明，通过CO诱导的聚集和动力学捕获控制在新的催化剂结构的合奏效果的可能性。
Platinum group metals (PGMs) serve as highly active catalysts in a variety of heterogeneous chemical processes. Unfortunately, their high activity is accompanied by a high affinity for CO and thus, PGMs are susceptible to poisoning. Alloying PGMs with metals exhibiting lower affinity to CO could be an effective strategy toward preventing such poisoning. In this work, we use density functional theory to demonstrate this strategy, focusing on highly dilute alloys of PGMs (Pd, Pt, Rh, Ir and Ni) with poison resistant coinage metal hosts (Cu, Ag, Au), such that individual PGM atoms are dispersed at the atomic limit forming single atom alloys (SAAs). We show that compared to the pure metals, CO exhibits lower binding strength on the majority of SAAs studied, and we use kinetic Monte Carlo simulation to obtain relevant temperature programed desorption spectra, which are found to be in good agreement with experiments. Additionally, we consider the effects of CO adsorption on the structure of SAAs. We calculate segregation energies which are indicative of the stability of dopant atoms in the bulk compared to the surface layer, as well as aggregation energies to determine the stability of isolated surface dopant atoms compared to dimer and trimer configurations. Our calculations reveal that CO adsorption induces dopant atom segregation into the surface layer for all SAAs considered here, whereas aggregation and island formation may be promoted or inhibited depending on alloy constitution and CO coverage. This observation suggests the possibility of controlling ensemble effects in novel catalyst architectures through CO-induced aggregation and kinetic trapping.