Adsorption of acetylene on Sn-doped Ni(111) surfaces: a density functional study

First-principle density functional theory calculations have been performed to investigate the adsorption of C₂H₂ on Ni(111) and Sn@Ni(111) at different coverages. At low coverage, the C₂H₂ molecule is strongly adsorbed on Ni(111) and the dissociation of the H atom is not favorable. Furthermore, the more the H atom dissociated, the more unstable the system is. However, the dissociation structure of C₂H+H has the largest adsorption energy on Sn@Ni(111), indicating that the dissociation structure is more stable than molecular adsorbed C₂H₂. At moderate coverage, there is some repulsive interaction between two C₂H₂ molecules, inducing the decrease in adsorption energy. On Ni(111), the two C₂H₂ tend to adsorb separately, however, the dimer C₄H₄ has the largest adsorption energy on Sn@Ni(111). At high coverage, the trimer derivative benzene has the largest adsorption energy on both Ni(111) and Sn@Ni(111) surfaces. The adsorption energies of the formed benzene are very high on the two systems, even larger than those of three individual adsorbed C₂H₂.