Interfacial properties of polycrystalline gold electrodes in tetraalkylammonium electrolytes

Abstract

Electrochemical properties of polycrystalline gold electrode in aqueous tetraalkylammonnium electrolyte solutions have been studied using cyclic voltammetry and impedance spectroscopy. Results obtained indicate that adsorption on the gold electrode depends on the number of carbon atoms in tetraalkylammonium cation. Tetramethylammonium cation is not adsorbed on gold, contrary to mercury and bismuth. Tetraethyl- and tetrapropylammonium cations are slightly adsorbed and tetrabutylammonium cation is strongly adsorbed with the possibility of formation of condensed layers at the electrode surface. However they are desorbed from the electrode surface by potassium cations, which are considered as not specifically adsorbed on the gold electrode. It was suggested that tetrabuthylammonium cations do not interact with the metal surface, but they are pushed out from the solution. The dependence of the double layer properties of tatraalkylammonium cations on the electrode material confirmed this suggestion. In the case of tetramethyl- and tetraethylammonium cations double layer capacity strongly depends on the metal but in the case of the strongest adsorbed tetrabutylammonium cations, capacity is metal independent. The dependence of anion follows the pattern observed previously on mercury electrode. Potential region in which the capacity is determined by the tetraalkylammonium cations becomes narrower with the increasing absorbability of anions. Capacity at far negative potentials increases with decreasing cation size and electrode ∣ electrolyte interface can be described as a condenser filled with electrolyte.