Abstract
Abstract : Surface enhanced Raman scattering has been used to detect in situ the formation of O= and OH- adsorbed on a Ag electrode in an aqueous solution of 25 micromolar Na2Cr2O7 and .01 to .001 M KC1. Both oxide and hydroxide adsorbates are observed after completion of an oxidation-reduction cycle in a standard voltammetry experiment. As the Ag electrode voltage is swept cathodically, the O=ads is protonated to form more OH-ads but, unlike in MnO4- solutions, no further protonation to form H20 occurs at any cell voltage. The addition of O2 gas to the electrolyte deprotonates the adsorbed OH- to form an oxide covered surface. These results for CrO4 solutions are contrasted with previous results for MnO4 electrolytes to obtain information about the nature of the metal-solution interface in chromate passivated metal surfaces. Keywords: Catalysis, Passivation, Metal surfaces, Protonation, Metal oxide absorbates, Silver, Electrodes, Hydroxides.
Published Version
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