Bromide Electrosorption on Liquid Gallium:  A Typical Example of Halide Electrosorption from Aqueous Solutions and Its Modeling

Abstract

The adsorption of bromide ion on liquid gallium from aqueous solutions of NaBr + HBr of concentrations ranging from 0.02 to 1.99 M was determined on the basis of capacitive charge measurements carried out by a computerized chronocoulometric technique. This adsorption is parametrized by the use of the virial isotherm corrected for the potential difference across the diffuse layer. The resulting adsorption behavior has several features in common with chloride, bromide, and iodide adsorption on mercury. These general features are interpreted on the basis of a molecular model that accounts for the local potential at the position of an adsorbed anion created by the surrounding anions as well as by the water dipoles. The fundamental role played by the mutual interactions among the adsorbed anions, the adsorbed water dipoles, and the inhomogeneous electron gas, the latter treated on the basis of a simple one-parameter jellium model, is pointed out.

Kinetics of Two-Dimensional Phase Transitions of Sulfide and Halide Ions on Ag(111)

“…Thus, ion−ion Coulombic repulsive forces are expected to decrease, in view of the progressively lower charge borne by the adsorbed ion. It should be noted, however, that Coulombic repulsive forces within the inner layer are notably screened by multiple imaging . A decrease in the charge located in the adsorbed anion causes not only a decrease in the repulsive Coulombic interaction when two like adsorbed anions approach each other but also a decrease in the attractive cosphere overlap energy arising from the overlap of the Born polarization regions about the two ions…”

“…It should be noted, however, that Coulombic repulsive forces within the inner layer are notably screened by multiple imaging. 67 A decrease in the charge located in the adsorbed anion causes not only a decrease in the repulsive Coulombic interaction when two like adsorbed anions approach each other but also a decrease in the attractive cosphere overlap energy arising from the overlap of the Born polarization regions about the two ions. 68 The lower the charge on the adsorbed anion, the lower the Born polarization energy of its two-dimensional primary solvation sheath; hence, the decrease in the Born polarization of water in the overlap region, due to the opposing field vectors created by the two approaching anions, will also decrease.…”