Why are trace amounts of chloride so highly surface-active?

JUAREZ, FERNANDA; QUAINO, PAOLA; COLOMBO, ESTEFANIA; SANTOS, ELIZABETH; JACKSON, MEGAN N.; SCHMICKLER, WOLFGANG

JOURNAL OF ELECTROANALYTICAL CHEMISTRY - (Print)

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2019

1572-6657

P On many E metals, small quantities of chloride are known to be adsorbedat potentials well below the potential of zero charge and to influence otherelectrochemical C processes. In order to understand this behavior, we have in-vestigated the adsorption of a single Cl− ion from aqueous solution by acombination C of density functional theory and classical molecular dynamics,taking A Au(111) as a model surface. While in the vacuum, Cl is adsorbed di-rectly on the surface in the 3-fold hollow sites, in aqueous solution the opti-mal position lies a fraction of an Ångstrom towards the solution, where theion is almost fully solvated and mobile in the direction parallel to the sur-face. As a result, the adsorption of a single ion is exothermic by about -0.6eV, even at the potential of zero charge. This adsorption behavior is limitedto low coverages, because the adsorbates repel each other and because fullsolvation shells can only form at low coverage.