engleski

Determination of the standard Gibbs free energy of transfer at the three-phase junction organic liquid˝aqueous solution˝graphite electrode

Drops of nitrobenzene and 1,2-dichloroethane containing solely 0.1 mol/L decamethylferrocene (dmfc) are attached to the surface of a paraffin-impregnated graphite electrode and immersed into various aqueous electrolytes. The oxidation of dmfc and the re-reduction of the cation dmfc+ are enabled by the simultaneous transfers of anions between the aqueous electrolyte and the organic solvents. The reaction starts at the three-phase junction. A linear relationship is observed between the formal potentials of dmfc and the standard Galvani potential differences of the used anions, and the influence of anion concentration on the intercepts of these straight lines is explained. The standard Gibbs energies of transfer of acetate and sulfate on the water˝nitrobenzene interfaces were determined as: = 33.4 kJ/mol, = 81.4 kJ/mol. The values for the transfer of acetate and sulfate at the water ˝dichloroethane interface could not be precisely determined, however the following ranges seem to be most probable: = (42.5 - 51.3) kJ/mol and = (76.2 - 90,7) kJ/mol. Finally, the applicability of square-wave voltammetry for ion transfer measurements at three-phase junctions is discussed.

ion transfer; Gibbs free energy; cyclic voltammetry; three-phase junction; nitrobenzene; 1;2-dichloroethane;

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