Thermodynamics of ideal polarizable interfaces

Abstract

Here we extend on the brief introduction of the surface tension given in Chap. 4. To a large extent, our treatment is based on the works of Grahame [1] and Parsons [2] and, like all proper thermodynamics, is exact. However, our way of defining the surface tension and deriving its differential is different, and is based on a discussion with H. Ibach, whose book contains an alternative derivation directed at solid electrodes [3]. In the classical derivation, the surface tension is introduced ad hoc, and it is not clear that it has the potential as its natural variable. For liquid electrodes thermodynamics offers a precise way to determine the surface charge and the surface excesses of a species. This is one of the reasons why much of the early work in electrochemistry was performed on liquid electrodes, particularly on mercury – another reason is that it is easier to generate clean liquid surfaces than clean solid surfaces. With some caveats and modifications, thermodynamic relations can also be applied to solid surfaces, and it is still the most exact way to obtain surface excesses.