A comparative ab initio study of acetylene activation over Au9 cluster and Au9 supported over ZnO monolayer

Abstract

A plane wave density functional theory has been employed to investigate acetylene activation over Au9 cluster and the same supported over single layer ZnO. Adsorption of C2H2 over gold clusters adopts the π mode and σ mode. The σ mode of adsorption is preferable as two C atoms bind to least coordinated Au atoms in Aun cluster. Adsorption energy of C2H2 over Au9 is increases from 0.47 eV to 0.87 eV when Au9 is supported on the ZnO single layer.Significantly lower activation energy barrier for acetylene activation (0.08 eV) has been found for Au9/ZnO in comparison to the same over Au9 cluster (2.14 eV). The lowering in the activation energy barrier is attributable to the reduction of Au9: The underlying ZnO monolayer transfers electronic charge to Au9 and thereby reduces it. It is supported by upshift in the Fermi level of the ZnO single layer by 0.47 eV towards higher energies upon hosting Au9. These results provide useful pointers in optimizing the catalytic processes via an appropriate choice of support for metal clusters serving as catalysts.