Wetting Behaviour of Gold Electrode and Molten Alkali Chlorides

The potential dependence of the contact angle between a gold electrode and lithium, sodium, potassium, rubidium, and caesium chloride melts was studied using the meniscus weight method to establish the patterns of wettability of solid surfaces by ionic melts when changing the composition of the salt phase and the jump of the electric potential. It is found that the forms of the contact angle versus the potential curve of Au change from a convex to a camel-like shape with two maxima upon replacing the lithium chloride with the caesium chloride melt. This phenomenon is explained by the assumption that the adsorption of the halide anions at the positively charged electrode surface has a chemical rather than electrostatic character. The adsorption process is accompanied by a charge transfer through the interface and the formation of covalent bonds between the adsorbent and adsorbate.