Colloque

Electrochemical Adsorption of Organic Bases and their Conjugate Acids

B.E. Conway

R.G. Barradas

Membre a labase

B.E. Conway

Résumé du colloque

Following previous studies on solid metals, electrocapillary measurements are reported for the adsorption of a series of heterocyclic and aromatic bases (and their ions) at the mercury electrode. The adsorption isotherms are derived for various electrode potentials and standard free energies ΔG⁰ of adsorption are deduced and related to molecular and electronic structure of the adsorbates. Specific π-orbital interaction effects are indicated which determine the orientation of the bases at the electrode. It is shown that dipole interaction effects lead to variations of ΔG⁰ with the 3/2 power of surface coverage θ; this prediction is confirmed experimentally. The variation of ΔG⁰ with θ 3/2 has two distinct linear regions, the change of slope ( ∂ΔG⁰ / ∂θ3/2 )E being related to molecular orientation at high fields and coverages. The effects are closely related to the shifts of the potential of the electrocapillary maximum ( e.c.m. ) observed in the solutions of the bases. The observed ΔG⁰ values at the e.c.m. are related to those found for adsorption of two bases at the air/water interface.

Contexte

Section :

Chimie physique

Thème du colloque :

Chimie physique

Responsables :

Ludovic Ouellet

Hôte : Université Laval

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