A UNIFIED TREATMENT OF THE EQUILIBRIUM PROPERTIES OF ELECTROSORBED LAYERS COMPOSED OF NEUTRAL AND IONIC SPECIES

Classical thermodynamics is used in combination with the electrostatic theory to develop generalized expressions for the electrochemical pot entials of neutral and ionic species of multicomponent layers adsorbed on electrode surfaces. The proposed approach allows all kinds of dipo le-dipole, field-dipole, ion-field and ion-image interactions to be re adily taken into account. The electrochemical potentials are used for the derivation of the equilibrium equations, ie the adsorption isother ms and the equation of state. A number of limiting cases of the multic omponent adsorption are briefly examined. The attention is focused on the effect of the specific adsorption of anions on the adsorption feat ures of a neutral organic adsorbate. It is found that the theoretical predictions are in general agreement with experiment. The most interes ting of the predicted properties is the increase in the adsorption of an organic adsorbate in the presence of adsorbed anions when the elect rode charge density is used as the independent electrical variable. In direct experimental evidences of this phenomenon are presented from li terature and an explanation within the framework of our theory is give n. Copyright (C) 1996 Elsevier Science Ltd