Contribution of the metal to the differential capacity of an ideally polarisable electrode
Abstract
We consider the response of the metal in the ideally polarisable electrode to charging of the electrode, using a model for the metal surface in contact with the solvent of the electrolyte phase previously presented by us in this journal. We show that the effect of the solvent on the electrons of the metal cannot be considered to be simply that of a repulsive barrier. When the electrode charge varies qM(dip), the metal contribution to the double layer, is modified, implying a contribution which varies along the electrocapillary curve. By considering an electrostatic interaction between metal and solvent, we find an acceptable value for the contribution of the metal to the double-layer capacity. Furthermore, the introduction of appropriate parameters for the metals shows that one should expect CGa>CHg at the potential of zero charge, in accord with experimental observations. The influence of the choice of parameters, particularly those which express the interpenetration of metal and solvent in our model, is discussed as well as other possible models. The different contributions of electrons of different metals probably need to be considered in evaluating models for the inner-layer contribution to the capacity.