In situ Spectroscopic Studies of the Metal-Electrolyte Interface

Abstract

Electrochemical interfaces are widely spread out in nature. In most of the spontaneous processes at a solid-liquid interfaces driving electric force generated by accidental heterogeneities acts at the solid surface coupled to non-uniform potential distribution. In an electrochemical system, the necessary physicochemical parameters (e.g., voltage or current, nature and composition of the electrolytic solution, etc.) can be empirically controlled in order to direct the course of a faradaic process. However, little is known about the influence of the nature of the metal side on the rate and mechanisms of these processes at a microscopic level. The need of ancillary spectroscopic techniques with molecular specificity and high sensitivity is steadly growing, particularly in connection with studies in electrocatalysis and energy conversion. A correct use of these techniques and a proper interpretation of the experimental results connot abstain from considering the possible perturbing effect produced by the strong inter- facial electric field on the electronic and vibrational energy of the reacting species. This is a consequence of the Fermi-Thomas screening of the potential inside the metal (within ca. 0.5 Å) and its deployment in the solution side within a distance of a few Ångstroms. So that, even a potential of 1 V away from the potential of zero charge applied to the metal can produce a field of more than 10⁷ V/cm across the first layer of the solvent (e.g., water) adsorbed onto the electrode.