B3LYP and in Situ ATR-SEIRAS Study of the Infrared Behavior and Bonding Mode of Adsorbed Acetate Anions on Silver Thin-Film Electrodes

The adsorption of acetate anions on silver thin-film electrodes has been studied by in situ infrared spectroscopy experiments and density functional theory calculations. Stable silver thin films were deposited either chemically or by argon sputtering on germanium and silicon substrates, respectively, and used as electrodes under internal total reflection conditions (ATR-SEIRAS) with a Kretschmann configuration. B3LYP harmonic IR frequencies of acetate species adsorbed with different geometries on Ag clusters with (111), (100), and (110) orientations have been calculated using LANL2DZ ECP and 6-311++G** basis set. The theoretical and experimental results confirm that bonding of acetate to the surface involves the two oxygen atoms of the carboxylate group, with the O−C−O plane perpendicular to the metal surface. The calculated frequencies reveal that the surface crystallographic orientation and total charge have little effect on the vibrational frequencies of adsorbed acetate species.