Fluctuations of concentration overpotential generated at gas-evolving electrodes

The electrode overpotential is usually expressed in terms of partial components related to ohmic, activation and concentration effects. For a gas-evolving electrode, the overpotential fluctuates because of bubble evolution but only the global overpotential fluctuations and, more recently, their ohmi...

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Bibliographic Details
Published in:Electrochimica acta 2005-06, Vol.50 (18), p.3726-3736
Main Authors: Gabrielli, C., Huet, F., Nogueira, R.P.
Format: Article
Language:English
Subjects:
Chemical Sciences
Chemistry
Concentration overpotential
Electrochemical noise
Electrochemistry
Electrodes: preparations and properties
Electrolyte resistance fluctuations
Exact sciences and technology
Gas cavity
Gas-evolving electrodes
General and physical chemistry
Material chemistry
Other electrodes
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Summary:The electrode overpotential is usually expressed in terms of partial components related to ohmic, activation and concentration effects. For a gas-evolving electrode, the overpotential fluctuates because of bubble evolution but only the global overpotential fluctuations and, more recently, their ohmic part are easily accessible by routine experiments. In the present paper, high-amplitude fluctuations of concentration overpotential have been experimentally revealed by an anomalous behaviour of the current fluctuations induced by hydrogen evolution on platinum electrodes under potential control in alkaline media with or without the presence of a second mass-transport-controlled reaction. Inverted current jumps, reproducibly observed owing to an artificial bubble-nucleation site created on the edge of the rotating electrode, which provoked periodic bubble eruption, were ascribed to local concentration changes drastically affecting the current-lines distribution. These experimental results validate the theoretical models that predicted those anomalies but remained unverified up to now. A quantitative estimation of each overpotential component at bubble eruption is addressed by means of a simplified analytical approach supported by the simultaneous measurement of the electrochemical current noise and electrolyte resistance fluctuations.
ISSN:0013-4686
1873-3859
DOI:10.1016/j.electacta.2005.01.019