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Schlagwörter:
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Zusammenfassung:
Stationary and rotating disc electrode voltammetry are employed to study the kinetics of the peroxodisulfate reduction to sulfate on Au(110) and Au(111) electrodes in the perchloric acid solution. The surface and the interfacial structure of these electrodes are examined by ex-situ STM and impedance measurements, respectively. Strong adsorption of peroxodisulfate and/or sulfate on both surfaces is observed, which has the superequivalent character, and which is controlled mainly by the charge on the metal. The surface structure and symmetry of the Au(111) surface allows for a more effective overlap of the electronic wave functions of the metal and the adsorbed peroxodisulfate, which results in a two order of magnitude faster electron transfer than on Au(110). On negatively charged surfaces, the rate of this electroctalytic pathway is limited by the decreasing surface concentration of peroxodisulfate, while the rate of the electron transfer to the solution species (the direct pathway) can be measured. Its correction for the double layer effect reveals that the true kinetic parameters of the direct pathway have essentially the same values for both electrodes. A comparison of the kinetic behaviour of the flame-annealed and non-annealed Au(111) electrodes throws some light on the role of the steps on the metal surface.
