Theoretical Insights into the Reaction Mechanisms of CO Oxidation Catalyzed by Al ₁₂ X (X = Be, Al, C, and P) Superatoms: The Number of Valence Electrons Determines?

The reaction mechanisms of CO oxidation catalyzed by Al₁₂X (X = Be, Al, C, and P) superatoms have been systemically investigated by density functional theory (DFT) calculations in this study. The adsorption behaviors of O₂ and CO onto these four Al₁₂X superatoms were compared, and typical CO oxidation mechanisms, including Eley-Rideal (ER), Langmuir-Hinshelwood (LH), and Trimolecular Langmuir-Hinshelwood (TLH) mechanisms, were studied in detail to elucidate the effects of the valence electron number of superatoms on the adsorption and catalytic performances. Our results demonstrate that Al₁₂X superatoms exhibit preferential adsorption toward O₂ over CO, where the interfacial electron transfer from such clusters to the adsorbates plays a pivotal role in the activation of adsorbed molecules. The degree of activation of O₂ on the Al₁₂X surface is closely related to the number of valence electrons of these superatoms. However, the rate-determining energy barrier of CO oxidation catalyzed by Al₁₂X has no significant correlation to the number of valence electrons. In particular, it is interesting to find that the Al₁₂C superatom with a magic number of 40 valence electrons achieves the best CO oxidation performance through the TLH pathway, exhibiting a low activation barrier of 11.54 kcal/mol. This work not only provides new insights into the effect of electronic structures of superatoms on their catalytic activity but also offers theoretical guidance for the design of new superatom catalysts with high performance.