Significance of Effects of High Pressure on Kinetics of Electrode Reactions: II . The Nature of Solvent Reorganization in the Activation Process of an Electrochemical Redox Reaction

Abstract

New information on the nature of the solvent reorganization process involved in formation of the transition state in an electrochemical redox reaction [the couple] is given by studies of the kinetics of this process at high pressures in aqueous solutions at Au. The apparent activation volume is evaluated together with the true volumes of activation for the forward and reverse directions of the redox reaction. By means of calculations of the electrostriction associated with the long‐range dielectric polarization in comparison with that associated with ion‐solvent interaction in the primary hydration shell, it is shown that the activation process must be mainly (75%) due to short‐range solvent reorganization in the primary shell. This is contrary to what has often been assumed in the interpretation of the energy of activation of ionic redox reactions. The experiments also allow some deduction to be made about the “symmetry” of the transition states in the electrochemical reaction in comparison with that in the corresponding homogeneous reaction, in so far as solvent reorganization is concerned.