Gas–particle
interfaces are chemically active environments.
This study investigates the reactivity of SO2on NaCl surfaces
using advanced experimental and theoretical methods with a NH4Cl substrate also examined for cation effects. Results show
that NaCl surfaces rapidly convert to Na2SO4with a new chlorine component when exposed to SO2under
low humidity. In contrast, NH4Cl surfaces have limited
SO2uptake and do not change significantly. Depth profiles
reveal transformed layers and elemental ratios at the crystal surfaces.
The chlorine species detected originates from Cl–expelled from the NaCl crystal structure, as determined by atomistic
density functional theory calculations. Molecular dynamics simulations
highlight the chemically active NaCl surface environment, driven by
a strong interfacial electric field and the presence of sub-monolayer
water coverage. These findings underscore the chemical activity of
salt surfaces and the unexpected chemistry that arises from their
interaction with interfacial water, even under very dry conditions.