engleski

Reversible redox reaction complicated by the reactant adsorption

Pulse voltammetric techniques are very sensitive to the anion-induced adsorption of metal ions on mercury electrodes [1,2]. In some cases, such as the adsorption of neutral complex PbBr2 [3], the response may consist of the diffusion and adsorption waves, while in other cases a single peak appears regardless of metal ion concentration [4]. In the former case, a sampled dc polarogram consists of a main wave and a post-wave that are separated by the minimum [5]. In this communication the influence of the reactant adsorption on dc polarograms and pulse, differential pulse and square-wave voltammograms of a reversible redox reaction on a stationary spherical electrode is investigated theoretically for Langmuir and Frumkin isotherms. The responses depend on lateral interactions in the monolayer. Indications of attractions between the adsorbed molecules are the continuous shift of peak potentials of the post-peaks towards lesser values, the splitting of the post-peak and the minimum followed by very steep post-wave. The repulsion forces prevent the separation of diffusion and adsorption waves. The model applies to adsorptive accumulation of ions of amalgam-forming metals.

cyclic staircase voltammetry; adsorption; microelectrode

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