Recent studies have shown that the addition of Cu to Ag catalysts improves their epoxidation performance by increasing the overall selectivity of the bimetallic catalyst. We have prepared AgCu near-surface alloys and used scanning tunneling microscopy to gain an atomistic picture of O₂ dissociation on the bimetallic system. These data reveal a higher dissociative sticking probability for O₂ on AgCu than on Ag(111), and density functional theory (DFT) confirms that the O₂ dissociation barrier is 0.17 eV lower on the alloy. Surprisingly, we find that, after a slow initial uptake of O₂, the sticking probability increases exponentially. Further DFT calculations indicate that surface oxygen reverses the segregation energy for AgCu, stabilizing Cu atoms in the Ag layer. These single Cu atoms in the Ag surface are found to significantly lower the O₂ dissociation barrier. Together, these results explain nonlinear effects in the activation of O₂ on this catalytically relevant surface alloy.

中文翻译：

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动态重组在AgCu近表面合金上诱导氧活化。

最近的研究表明，向Ag催化剂中添加Cu可通过提高双金属催化剂的整体选择性来改善其环氧化性能。我们已经制备了AgCu近表面合金，并使用扫描隧道显微镜获得了双金属体系上O ₂离解的原子图。这些数据表明，O ₂在AgCu上的离解粘附几率高于在Ag（111）上，并且密度泛函理论（DFT）证实，O ₂在合金上的解离势垒低0.17 eV。令人惊讶的是，我们发现，在缓慢吸收初始O _2之后，粘着几率成倍增加。进一步的DFT计算表明，表面氧逆转了AgCu的偏析能，从而稳定了Ag层中的Cu原子。发现Ag表面中的这些单个Cu原子显着降低了O _2的解离势垒。总之，这些结果解释了在该催化相关表面合金上O ₂活化中的非线性效应。