The dependence of the exchange current density of the ferric/ferrous reaction on electrode surfaces has been investigated using the work functions of metals, surface potentials of the reactants, adsorption characteristics of water dipoles, hydration numbers, etc. The extent of dehydration of the reactant species at the reaction zone, as well as the influence of desorption of water dipoles from the electrode surface on the magnitude of exchange current density, is demonstrated. (C) 2004 Elsevier Inc. All rights reserved.