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Charging of Silver Bromide Aqueous Interface: Evaluation of Enthalpy and Entropy of Interfacial Reactions from Surface Potential Data

Dependence of inner surface potential (Ψ0) at the silver bromide aqueous electrolyte interface was measured as a function of activities of Br– and Ag+ by using a single crystal silver bromide electrode (SCr-AgBr). Absolute values of surface potentials were obtained from isoelectric points. Measurements were performed at different temperatures in the range from 10 to 50°C. Corresponding equilibrium constants of interfacial reactions were obtained using Surface Complexation Model and interpreted via the van't Hoff equation. As a result of the interpretation for the binding of bromide ions leading to a negative surface charge, the following thermodynamic parameters were obtained: ; , while for the binding of silver ions leading to a positive surface charge, these parameters were obtained: ; . Association of counterions (CI) with oppositely charged surface sites partially compensate the surface charge. Assuming approximately the same affinities for anions ( ) and cations (K+) thermodynamic parameters for their binding were obtained as: ; .

silver bromide; single crystal electrode; surface potential; interfacial equilibrium constants; enthalpy; entropy

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