Differential capacitance of polycrystalline zinc Part II. Effect of amalgamation and tetraalkylammonium ions

Abstract

Differential capacity measurements have been made in aqueous solutions of NaClO4 and in these solutions containing Pr4NCl and Bu4NBr using a polished polycrystalline zinc electrode amalgamated to three different microgram levels. It is postulated that mercury has the effect of etching the zinc surface probably by preferentially attacking the grain boundaries and this change in the physical state of the electrode influences not only the extent of adsorption of tetraalkylammonium cations but also their general adsorption characteristics. It is also suggested that amalgamation does not appreciably affect the chemical nature of the electrode since in neutral solutions strong OH− ion interaction with the surface occurs at the same potential as that for an unamalgamated electrode. This paper therefore re-emphasises the importance of the physical state of the electrode surface in the determination of the characteristic double layer capacity of solid electrodes.