Electrochemical Studies of the Benzoate Adsorption on Au (111) Electrode |
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Authors: | Hong-Qiang Li Sharon G. Roscoe Jacek Lipkowski |
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Affiliation: | (1) Guelph-Waterloo Centre for Graduate Work in Chemistry, Guelph Campus, University of Guelph, Ontario, N1G 2W1, Canada;(2) Department of Chemistry, Acadia University, Wolfville, Nova Scotia, B0P 1X0, Canada |
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Abstract: | Cyclic voltammetry (CV), differential capacity (DC), and charge densitymeasurements have been employed to study the benzoate (BZ) adsorption at the Au(111)electrode surface. Thermodynamic analysis of charge density ( M) data has beenperformed to describe the properties of the adsorbed benzoate ion. The Gibbsexcess , Gibbs energy of adsorption G, and the number of electrons flowingto the interface per adsorbed benzoate ion at a constant potential (electrosorptionvalency) and at a constant bulk concentration of the benzoate (reciprocal of theEsin—Markov coefficient) have been determined. The results demonstrate thatalthough benzoate adsorption starts at negative charge densities, it takes placepredominantly at a positively charged surface. At the most positive potentials,the surface concentration of benzoate attains a limiting value of about 7.3×10–10mol-cm–2, which is independent of the bulk benzoate concentration. This valueis consistent with packing density corresponding to a closed-packed monolayerof vertically adsorbed benzoate molecules. At negative charge densities, benzoateassumes a flat ( -bonded) surface coordination. The surface coordination ofbenzoate changes, by moving from a negatively to positively charged surface.At the negatively charged surface, the electrosorption bond is quite polar. Thepolarity of the chemisorption bond is significantly reduced due either to a chargetransfer or a screening of the charge on the anion by the charge on the metal. |
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Keywords: | Benzoate adsorption Au(111) electrode chronocoulometry |
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