Chronocoulometric measurements of azobenzene adsorption on mercury from water + ethanol mixtures of different composition

Abstract

Chronocoulometric measurements of azobenzene adsorption on mercury at –0.430 V/s.c.e. from water + ethanol mixtures are reported. Having assumed that, at ethanol concentrations C^*₁ > 4 mol dm^–3, water adsorption at the chosen potential is negligible, we interpreted the adsorption data by using the adsorption isotherm KC^*₁/C^*n₂=θ₁ e/n^αθ1(1-θ₁)ⁿ, where C^*₁ and θ₁ are the bulk concentration and the surface coverage by azobenzene, n is the number of adsorbed ethanol molecules displaced by one azobenzene molecule, K is an adsorption coefficient and α is an interaction factor. The possibility of varying both C^*₁ and C^*₂ allows the configuration effect, due to a n value equal to 3, to be distinguished from the effect of adsorbate-adsorbate interactions, due to a nonzero α value. A statistical mechanical derivation of the isotherm employed is provided.