Quantitative understanding of the chemisorption on single-atom catalysts (SACs) by their electronic properties is crucial for the catalyst design. However, the physical mechanism is still under debate. Here, the CO catalytic oxidation on single transition metal (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Ni) dopants is used as a theoretical model to explore the correlations between the characteristics of electronic structures and the chemisorption on SACs. For these metal dopants, their atomic d orbitals form several nondegenerate and localized electronic states that are found to be selectively coupled with the π* orbital of the adsorbed O₂, which we defined as selective orbital coupling. Based on the selective orbital coupling, we find that the alignment between the selected d state and the π* state determines the bond strength, regardless of the electron occupation number of the selected d states; the electron transfer to form M–O bonding can be provided by the support. Such electron transfer can be related with the electronic metal–support interaction. We attribute the origin of the chemisorption mechanism to the coexistence of the localized orbital of the single transition metal and the continuous energy band of the Au support. Finally, we illustrate how this mechanism dominates the variation trend of the reaction barriers. Our results unravel a fundamental adsorption mechanism in SAC systems.

中文翻译：

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选择性轨道耦合：单原子催化中的吸附机制

通过单原子催化剂（SAC）的电子特性定量了解其化学吸附对于催化剂设计至关重要。然而，其物理机制仍存在争议。本文以单一过渡金属（即Sc、Ti、V、Cr、Mn、Fe、Co、Ni）掺杂剂上的CO催化氧化作为理论模型，探讨电子结构特征与化学吸附之间的相关性。 SAC。对于这些金属掺杂剂，它们的原子d轨道形成几个非简并的局域电子态，这些电子态被发现与吸附的 O ₂的 π* 轨道选择性耦合，我们将其定义为选择性轨道耦合。基于选择性轨道耦合，我们发现，无论所选d态的电子占据数如何，所选d态和π*态之间的排列决定了键强度；形成M-O键合的电子转移可以由载体提供。这种电子转移可能与电子金属-载体相互作用有关。我们将化学吸附机制的起源归因于单一过渡金属的定域轨道和金载体的连续能带的共存。最后，我们说明了该机制如何主导反应势垒的变化趋势。我们的结果揭示了 SAC 系统中的基本吸附机制。