Large variations in the propensity of aqueous oxychiorine anionsfor the solution/vapor interface

摘要

Core-level photoelectron spectroscopy measurements have been performed of aqueous solutions ofNaCl codissolved with NaClO_n(n= 1-4).Each species has a distinct Cl 2p electron binding energy,which can be exploited for depth-profiling experiments to study the competition between Cl~-andClO_n~-anions for residing in the outermost layers of solution/vapor interface. Strongestpropensity for the surface is observed for n=4 (perchlorate), followed by n =3 (chlorate), n=2(chlorite), n =0 (chloride), and n=1 (hypochlorite). Molecular dynamics simulations rationalize thegreatest surface propensity of the most oxidized anions in terms of their larger size andpolarizability. The anomalous behavior of hypochlorite, being less surface-active than chloride,although it is both larger and more polarizable, is suggested to arise from the charge asymmetry overthe anion, increasing its efficiency for bulk solvation.