Abstract
The adsorption of benzonitrile (BN) at a gold (111) single crystal electrode has been investigated quantitatively using chronocoulometry. The procedure described in this paper differs slightly from previous work in that experiments were performed not only in neutral pH solutions but also at pH 2.4 in order to shift the potential corresponding to the oxidation of the metal surface toward more positive values and hence extend the double layer region effectively. The following adsorption parameters: film pressure, Gibbs surface excess, Gibbs energy of adsorption and electrosorption valency, were determined as functions of the electrode potential and the charge density for concentrations of BN up to 0.03 M (close to saturation). The values of the relative Gibbs excess indicate that adsorbed BN molecules are oriented parallel to the electrode surface at negative and moderately positive potentials and low bulk concentrations. The Gibbs energy at maximum adsorption is equal to −27 kJ mol −1 which suggests that BN is chemisorbed weakly on Au(111). The results presented here are compared with those obtained from other studies of BN adsorption on gold and mercury.
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