THERMODYNAMIC DERIVATION AND MODEL-CALCULATIONS OF THE METAL UNDERPOTENTIAL DEPENDENCE ON ELECTRON WORK FUNCTION DIFFERENCES

The relationship between the work function of the substrate + adsorbat e system and the underpotential shift is derived from a thermodynamic argument. An alternative explanation of the correlation formulated in the literature between the underpotential shift and the work function difference of the metals involved is proposed. A simple model is used to illustrate the meaning of the equations derived. Abrupt adsorption- desorption behaviour is predicted for those electrochemical systems wh ere the work function shows a pronounced minimum as a function of the coverage, provided that this is a first-order contribution to the chem ical potential of the system.