STUDY OF THE GOLD - AQUEOUS-ELECTROLYTE INTERPHASE BY MODULATED REFLECTION SPECTROSCOPY

The admittance and differential reflectivity of an electrode of polycrystalline gold in contact with aqueous 0.02 M NaF, KClO4, 0.01 M Na2SO4 and KCl have been measured in the range of potential where the electrode is ideally polarized (-0.7 V to 0.8 V NHE). In NaF and KClO4 evidence was obtained for the compression of the adsorbed layer of water. The increase of the number of water molecules, with respect to the number in the least original state (at-4μC cm-2), is 3% at +8 μC cm-2 and at-17 μC cm-2. At the potential of zero charge the water dipoles are oriented preferentially with the oxygen towards the metal. In KCl the optical measurements confirm the existence of two types of Au-Cl- interaction and the covalent character of the bond at the most positive charges. © 1979 Elsevier Sequoia S.A.