Adsorption and Co‐adsorption of Chlorine and Water‐Chlorine Complexes on Au(111) Surfaces: First‐Principles DFT Study

Abstract The adsorption of atomic chlorine (Cl) on perfect Au(111) surfaces has been investigated by employing extensive density functional theory calculations, including the Cl coverage range from 1/9 to 1 monolayer (ML) and the effect of water on the Cl adsorption. The structural, energetic, and electronic properties are calculated and compared with previously reported experimental studies towards adsorption of Cl on metal surfaces. We found that there is a significant difference in energy and electronic structures for adsorption of Cl at the top site, compared with adsorption of Cl on other sites of the Au surface. Surface coverage lower than 1/3 ML is enough for the adsorption of Cl atoms at an fcc hollow site, whereas the Cl adopts a mixed adsorption sites at higher coverage reaching 3/4 ML. The negatively charged Cl − ion increase the work function of the Au(111) surface at all coverage, and the Au−Cl interaction is dominated by a strong coupling between the d‐band of Au and the p state of Cl atoms. The appearance of water molecules makes Cl more stable for adsorbing on the top site of Au (111) through hydrogen bonding interaction, and also promotes interfacial charge transfer between Cl and Au(111). We emphasize here is that the Au−Cl stretching vibrational frequency at the top site is similar to the observed values in the experiment, while the Au−Cl stretching frequency redshifts as the coverage increases for Cl adsorped at the fcc site. The presence of water would cause a significant redshift of the Au−Cl stretching vibrational frequency because of the stretched bond length and the decrease of the covalent bonding component. These changes motivate us to rethink of the Au−Cl vibration frequency and the corresponding interfacial structure.