Structure and Decomposition Pathways of Vinyl Acetate on Clean and Oxygen-Covered Pd(100)

The surface chemistry of vinyl acetate monomer (VAM) on clean and oxygen-covered Pd(100) is explored experimentally in ultrahigh vacuum using reflection absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), and temperature-programmed desorption (TPD), combined with density functional theory (DFT) calculations. Both RAIRS and DFT calculations show that VAM adsorbs onto clean Pd(100) with its molecular plane close to parallel to the surface with the vinyl group bonded to a single palladium atom, which decomposes by a pathway initiated either by vinyl-acetate or vinyloxy-acetyl bond scission, where the former pathway predominates. VAM adsorbs on p(2 x 2)-O/Pd(100) and c(2 x 2)-O/Pd(100) in a geometry in which the acetate group moves away from the surface in an adsorption site in which the vinyl group is located over two palladium atoms, where this geometry is induced by a repulsion between the acetate groups and adsorbed oxygen. Decomposition on oxygen-covered surfaces is initiated exclusively by vinyl-acetate bond scission presumably since, in this case, vinyloxy-acetyl bond scission is inhibited since the acetate group is remote from the surface.