Interfacial excess entropies and solvent structures

Abstract

Detailed consideration is given to thermodynamic relationships describing the temperature dependence of the properties of electrified interfaces. Excess entropies are derived for multicomponent systems and in particular it is shown that the effect on the residual excess entropy, S*, of the specifically adsorbed organic species can be directly determined by experiment. Values of S* in the presence of thiourea (TU) can be understood in terms of the surface excesses of TU and the degree of solvent orientation. The preferred orientation of water is shown to be charge-dependent, under all conditions to be zero at −3 µC cm−2, and largely determined by its molecular polarisability. Temperature-invariant capacities are shown to occur widely and are not easily explained in terms of cluster models or time-dependent solvent orientation.