Autocatalytic mechanism of H sub(2)O sub(2) reduction on Ag electrodes in acidic electrolyte: Experiments and simulations

It is shown that the cathodic reduction of hydrogen peroxide (H sub(2)O sub(2)) on silver electrodes in acidic electrolyte can proceed by two parallel mechanisms: first, by the `normal' mechanism that has been discussed in the literature, second, by a novel mechanism proceeding at a significant...

Full description

Saved in:
Bibliographic Details
Published in:Electrochimica acta 1999-01, Vol.44 (25), p.4499-4506
Main Authors: Flaetgen, Georg, Wasle, Sabine, Luebke, Margot, Eickes, Christian, Radhakrishnan, Ganesan, Doblhofer, Karl, Ertl, Gerhard
Format: Article
Language:English
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:It is shown that the cathodic reduction of hydrogen peroxide (H sub(2)O sub(2)) on silver electrodes in acidic electrolyte can proceed by two parallel mechanisms: first, by the `normal' mechanism that has been discussed in the literature, second, by a novel mechanism proceeding at a significantly more positive potential. It is proposed that the second mechanism involves the activating adsorbate (OH) sub(ad), that forms in the course of the H sub(2)O sub(2) reduction reaction as an unstable intermediate. The coverage of the electrode with (OH) sub(ad) increases with the rate of H sub(2)O sub(2) reduction, i.e., the process is autocatalytic. At more negative potentials the coverage decreases as the rate of adsorbate reduction/desorption rises. This leads to a potential region of negative differential charge-transfer resistance and thus to complex dynamic phenomena, in particular to electrochemical oscillations. Model calculations based on these considerations yield the potential dependent OH-adsorption, the N-shaped current /voltage curves and current oscillations that agree well with the experimental findings.
ISSN:0013-4686