Adsorption characteristics of Cl, H2O, and O2 on Cu(111) and their implications for initial corrosion susceptibility: a density functional theory study.

CONTEXT: Chloride-containing species, H2O, and O2 are important environmental factors during the initial atmospheric corrosion of copper. In the present work, Cl- adsorption on Cu(111) was first investigated using a fully relaxed Cu model to characterize chloride-induced structural reconstruction and electronic activation. H2O and O2 were subsequently introduced to examine their additional co-adsorption effects on the chloride-affected Cu surface under simplified conditions representing humid and oxygen-containing environments. The introduction of Cl- induces pronounced local Cu-atom displacement, surface reconstruction, lattice distortion, and redistribution of the Cl-derived and Cu-derived electronic states. The subsequent addition of H2O and O2 further modifies the adsorption geometry and interfacial electronic environment. These results provide atomistic insight into chloride-induced surface activation relevant to the initial stage of copper corrosion, but they are not interpreted as direct proof of Cu dissolution or crystalline copper-chloride formation. METHODS: Density functional theory calculations were performed using a three-layer, nonuniform Cu(111)-derived model containing 121 Cu atoms. Two structural-relaxation protocols were adopted according to the purposes of the calculations. For the initial Cl-/Cu(111) systems used to examine chloride-induced reconstruction, all Cu atoms and the Cl- species were allowed to relax without positional constraints. After the optimized Cl/Cu(111) configuration had been obtained, H2O and O2 were introduced sequentially. In the subsequent co-adsorption calculations, all adsorbates and the Cu atoms in the outermost layer were allowed to relax, whereas the lower two Cu layers were fixed. Optimized structures, relaxation-inclusive adsorption energies, Hirshfeld charge redistribution, work-function changes, interlayer displacements, total density of states, and projected density of states were analyzed to characterize the structural and electronic responses of the investigated systems.