Activation Mechanism of the H2 on Au6-based Clusters From the Perspective of Chemical Bonding

Abstract

Recently, there is an interesting report (J. Am. Chem. Soc. 2020, 142, 13090–13101) on the photoinduced mechanism for the H₂ dissociation studied through a simple Au₆-H₂ model. However, the adsorption energy between the Au₆ and H₂ is only 0.25 eV, and the H─H bond length is only slightly longer. Based on the structural framework of the triangular Au₆, we have investigated the adsorptions of H₂ on the transition metals (TM = Ni, Cu, and Zn group elements) and revealed the differences in activation of H₂ on TM atoms. The results confirm that the activation of H₂ by the Au₅Ni cluster is the best in terms of the stability and adsorption energy (0.89 eV), where the H─H stretching frequency also has a very obvious redshift compared with the free H₂. The AIMD simulations show that the Au₅Ni-H₂ maintains an excellent thermal stability even at 500 K. The density of states, molecular orbitals, NCI-RDG, and bond order analyses indicate that the Ni∙∙∙H₂ and Au∙∙∙H₂ are rather strong, directly showing the bonding interactions. By studying H₂ adsorptions on TM atoms, one can obtain fundamental insight into elementary steps that take place on catalytically active surfaces.