T. Wandlowski

Double-layer dynamics in the adsorption of tetrabutyl ammonium ions at the mercury—water interface: I: Survey

Abstract 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.

Hydrogen bonding and two-dimensional condensation in uracils

Abstract The molecular organization in compact uracil films at the mercury/water interface is suggested to be a planar array of hydrogen—bonded molecules, similar to that found in the solid state.

Double-layer dynamics in the adsorption of tetrabutyl ammonium ions at the mercury-water interface: II: Capacitance transients

Abstract Capacitance-time transients show that the capacitance pit is formed by a process of nucleation and growth. The corresponding film can subsequently be transformed into another anion-containing film. Capacitance-time transients also provide evidence for the existence of a condensed layer containing anions at quite negative potentials.

Double-layer dynamics in the adsorption of tetrabutyl ammonium ions at the mercury water interface.: III. The admittance of the needle peak

Abstract The interfacial admittance at the needle peak contains a new element, dominant at low frequencies, owing to the growth and dissolution of patches of condensed film in the narrow region of potentials in which they coexist with areas not so covered. At sufficiently high adsorbate concentrations, the additional admittance can be represented by a series RC circuit in parallel to the usual desad admittance. Experimental results for tetrabutyl ammonium bromide in aqueous 0.5 M NaBr are reported; these can be represented well in terms of this model.

The condensation of 6-propyl-2-thiouracil at the mercury—electrolyte interface

Abstract At the mercury—water interface, 6-propyl-2-thiouracil in aqueous 0.5 M NaF exhibits several regions of interfacial condensation at sufficiently high adsorbate concentrations, including a metastable region. The kinetics of formation of these films are described.

Double-layer dynamics in the adsorption of tetrabutylammonium ions at the mercury | water interface Part 4. The reduction of hexammine-cobalt(III) through tetrabutylammonium films

Abstract The reduction of hexamminecobalt(III) at the mercury-water interface is strongly affected by the presence of a condensed tetrabutylammonium film. When the anions present are fluoride and/or tetrafluoroborate, electron transfer through the film proceeds via an inner-sphere mechanism, i.e. the film must be opened so that hexamminecobalt(III) can make direct contact with the metal. In the presence of bromide anions, an outer-sphere pathway is indicated, probably involving bridging by bromide ions. Unusual current-time transients of the reduction of hexamminecobalt(III) in the presence of tetrabutylammonium ions are correlated with the kinetics of film formation.

On the admittance of the needle peak

Abstract We respond to recent criticism (R.D. Armstrong, J. Electroanal. Chem., 372 (1994) 27) of our earlier paper on the admittance of the needle peak of tetrabutyl ammonium bromide at the mercury | water interface (J. Electroanal. Chem., 352 (1993) 279), and identify areas of serious misunderstanding.

Two-dimensional condensation of methylguanidinium nitrate at the mercury | water interface

Abstract Methylguanidinium nitrate can form a condensed interfacial monolayer, similar to that observed with guanidinium nitrate. However, the presence of the methyl group dramatically changes the effect of the salt monolayer on electrode kinetics.