Dependence of surface potential (electrostatic potential at the inner Helmholtz plane, Psi(0)) at the silver bromide aqueous electrolyte interface was measured as a function of the activities of Br- and Ag+ by using a single crystal silver bromide electrode (SCr-AgBr). Absolute values of surface potentials were obtained from electrode potentials of SCr-AgBr and isoelectric points. Measurements were performed at different temperatures in the range from 10 to 50 degrees C. Corresponding equilibrium constants of interfacial reactions were obtained using the 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 thermodynamic parameters obtained were Delta H-n degrees = 33 kJ mol(-1) and Delta S-n degrees = 31 J mol(-1) K-1; and for the binding of silver ions leading to a positive surface charge, Delta H-p degrees = 72 kJ mol(-1) and Delta S-p degrees = 196 J mol(-1) K-1. Association of counterions (CI) with oppositely charged surface sites partially compensates the surface charge. Assuming approximately the same affinities for anions (NO3-) and cations (K+) thermodynamic parameters for their binding were obtained as Delta H-Cl degrees 7 kJ mol(-1) and Delta S-Cl degrees approximate to 105 J mol(-1) K-1. (C) 2010 Elsevier Inc. All tights reserved.