Adsorption of acetylene on ordered NixAg1-x/Ni (111) and effect of Ag-dopant: A DFT study

The adsorption of acetylene molecules on the ordered Ni_xAg_1-x/Ni (111) (x = 1, 0.75, 0.5, 0.25) bimetallic surfaces was investigated by using the density functional theory (DFT). Among the model systems, Ni atom was replaced by Ag atom only on the top surface layer. The results show that, as the Ag concentration increases, the interaction between Ag-modified Ni_xAg_1-x/Ni (111) and acetylene molecules decreases gradually. Additionally, the adsorption processes of acetylene molecules on different considered surfaces are all exothermic thermodynamically. Furthermore, the Partial density states (PDOS) and the differential charge density properties suggest that an increase in atomic concentration of Ag in the upmost layer decreases the electron transfer between the acetylene molecule and surface. Our results could provide useful information to increase the activity of Ni-based catalysts for acetylene hydrogenation.