The morphology and charged state of gold clusters play a crucial role in heterogeneous catalysis. The selection and optimization of theoretical approaches are necessary for the investigation of active sites on isolated and supported gold clusters. In the present paper, a study of the potential isomers of the Au12 cluster is performed within the DFT/PBE framework using a scalar-relativistic approach. We have found Au12 to be a dynamic cluster with at least 24 isomers due to the Jahn–Teller distortion. The majority of these isomers exhibit low symmetry, resulting in the formation of low-coordinated atoms, which are discussed in terms of frontier molecular orbitals and a Hirschfeld analysis of their atomic charges. The energy difference between the most energetically stable 2D (D 3h ) and 3D (C 2v ) isomers of Au12 is small (equal to 25 kJ/mol), which is evidence of their coexistence. The influence of the support on properties of the cluster is investigated using Au12/MgO(100). The 2D isomer of Au12 can interact with the surface either in an upright position, with two (E ads/atom = 24 kJ/mol) or three atoms (E ads/atom = 25 kJ/mol); the preferred position is planar (E ads/atom = 30 kJ/mol). The small deformation energy is required to distort a dynamic structure of Au12 compared to rigid gold clusters. The 3D isomer interacts with MgO(100) with two of its atoms (E ads/atom = 24 kJ/mol). The Au–Au distances across the surface increase, whereas the Au–Au distances at an angle to the surface are compressed with respect to the distances in the free clusters. The weak adsorption energies of Au12 on MgO and the low activation barriers for gold atom migration (15 kJ/mol) between oxygen sites facilitate the diffusion of nanoparticles on the MgO surface.

Au, NiO, and NiO/Au clusters of 2.5-16 nm, supported on Al 2 O 3 , ZrO 2 , TiO 2 , and ZnO, were studied in the purification of ethene feedstock from ethyne by hydrogenation at 357 K. The Au, NiO, and NiO/Au catalysts possessed 100 % selectivity to ethene. As the size of NiO clusters decreased from 7 to 3 nm, the turnover frequency (TOF) decreased from 812-1,023 to 276 h −1 . In contrast with NiO, Au activity increased with decreasing particle size. NiO/Au catalysts possessed higher stability and activity in comparison with Au and NiO catalysts. The synergistic gain on NiO/Au clusters (SG) calculated as TOF NiO/Au -TOF Au -TOF NiO was 1,466; 1,147; 563; and 569 h −1 for NiO/Au/Al 2 O 3, NiO/Au/TiO 2 , NiO/Au/ZnO, and NiO/Au/ ZrO 2 , respectively. The reasons of the observed catalytic trends and the origin of the most active and selective sites are discussed.

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