DOUBLE-LAYER DYNAMICS IN THE ADSORPTION OF TETRABUTYL AMMONIUM-IONS AT THE MERCURY WATER INTERFACE

The literature shows that the adsorption behavior of tetrabutyl ammonium ions exhibits several rather unusual aspects. We report here that, below room temperature, the capacitance exhibits a pit region at low tetrabutyl ammonium concentrations. However, this capacitance pit may disappear at higher adsorbate concentrations. Capacitance-potential curves also provide evidence for the existence of distinct interfacial "states" outside the pit region. The appearance of needle-like capacitance peaks is associated with the existence of one such interfacial state, which clearly involves anion co-adsorption. Finally, the region of tetrabutyl ammonium adsorption is strongly influenced by competitive specific adsorption of both anions and cations, and provides direct evidence for the specific adsorption of common alkali cations at sufficiently negative potentials.