UNIVERSAL FUNCTIONAL-GROUP ACTIVITY-COEFFICIENT MODEL IN ELECTROSORPTION .2. ELECTROSORPTION OF 1-PROPANOL AT THE MERCURY SOLUTION INTERFACE

The electrosorption of 1-propanol on a mercury electrode from aqueous sodium sulfate solutions has been measured with a computer-controlled capillary electrometer. The data considered in the paper correspond to the temperature of 293.15 ± 0.05 K. Experimental conditions meet the requirements of the thermodynamic theory of electrocapillarity: the activity of the supporting electrolyte has been kept constant, electrode potential has been measured with respect to a sulfate ion reversible electrode, and the activity of adsorbate instead of its concentration has been used in the determination of the relative surface excess. The results have been interpreted in terms of the universal functional group activity coefficient (UNIFAC) theory of electrosorption (Karolczak, M. J. Electroanal. Chem. 1989, 262, 263). The activities of 1-propanol and water as well as the excess electrochemical Gibbs energies of mixing in the surface solution have been calculated at various electrode potentials. The dependence of the interaction energy parameters of various functional groups of the adsorbed compounds on the electrode potential has also been presented. It has been shown that the deviations from ideality are bigger in the surface solution of 1-propanol than they are in the corresponding bulk solutions. This observation has been related to the structure-making, structure-breaking effects of 1-propanol influenced by the electrical field at the interface. The obtained results support the appliance of the UNIFAC model in the electrosorption studies. © 1990 American Chemical Society.