How surface reparation prevents catalytic oxidation of carbon monoxide on atomic gold at defective magnesium oxide surfaces.
How surface reparation prevents catalytic oxidation of carbon monoxide on atomic gold at defective magnesium oxide surfaces.
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DOI：
10.1039/c6cp02339h
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发表时间：
2016-07
期刊：
影响因子：
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通讯作者：
K. Töpfer;J. Tremblay
中科院分区：
文献类型：
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作者：
K. Töpfer;J. Tremblay
在这篇文章中，我们利用第一原理研究了 CO 和 O2 在沉积在有缺陷的氧化镁表面的单个金原子上的共吸附和催化行为。使用密度泛函理论框架内的簇模型和点电荷嵌入，我们模拟了 Au1 在 MgO(001) 不同电荷的氧空位上的 CO 氧化反应，以合理化其实验观察到的催化活性缺乏。我们的结果表明：（1）F（0）和F（2+）缺陷处弱支持共吸附，但F（1+）位点不支持共吸附，（2）电子从F（0）空位通过Au1簇到吸附的分子氧的重新分布削弱了O2键，这是可持续催化循环所需的，（3）亚稳态碳酸酯中间体可以在F（0）型缺陷上形成，（4）对于非常有利的活性，仅存在很小的活化势垒CO2 从 F(0) 上解离，(5) F(0) 缺陷上金原子的适度吸附能不能阻止分子氧插入缺陷内。由于色心缺乏保护，表面总是被周围的氧气修复，并且催化循环在第一个氧化步骤中被不可逆地破坏。
In this contribution, we study using first principles the co-adsorption and catalytic behaviors of CO and O2 on a single gold atom deposited at defective magnesium oxide surfaces. Using cluster models and point charge embedding within a density functional theory framework, we simulate the CO oxidation reaction for Au1 on differently charged oxygen vacancies of MgO(001) to rationalize its experimentally observed lack of catalytic activity. Our results show that: (1) co-adsorption is weakly supported at F(0) and F(2+) defects but not at F(1+) sites, (2) electron redistribution from the F(0) vacancy via the Au1 cluster to the adsorbed molecular oxygen weakens the O2 bond, as required for a sustainable catalytic cycle, (3) a metastable carbonate intermediate can form on defects of the F(0) type, (4) only a small activation barrier exists for the highly favorable dissociation of CO2 from F(0), and (5) the moderate adsorption energy of the gold atom on the F(0) defect cannot prevent insertion of molecular oxygen inside the defect. Due to the lack of protection of the color centers, the surface becomes invariably repaired by the surrounding oxygen and the catalytic cycle is irreversibly broken in the first oxidation step.