Abstract
The emergence of Cl- ions from the surface of alkali halide salts at low relative humidity (RH) is predicted by density functional theory (DFT) calculations and supported by contact potential measurements. We find from DFT that, in the presence of water at the regime of one monolayer coverage on the (100) cleavage plane of NaCl, Cl- ions are displaced at very low energetic cost from their crystal lattice positions toward the plane of water molecules. Starting from plausible low-temperature layered structures, we use total energy DFT to calculate the energy cost to bring Cl- ions to the height of the water layer. We show the importance of the screening of the electrostatic interactions by the water layer in order to explain our findings and to determine the value of the surface dipole as a function of the chloride position. The theoretical surface dipole is used to estimate the concentration of raised Cl- ions at the surface. As dissolved chloride ions are the reactive component of the sea salt aerosols at high RH, we propose that the facile destabilization of Cl- is one of the mechanisms behind the catalytic activity of NaCl at low RH on reactions involving atmospheric gases.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call