Fluctuations of concentration overpotential generated at gas-evolving electrodes

C. Gabrielli, F. Huet, R. P. Nogueira

Research output: Contribution to journalArticlepeer-review

96 Scopus citations

Abstract

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.

Original languageBritish English
Pages (from-to)3726-3736
Number of pages11
JournalElectrochimica Acta
Volume50
Issue number18
DOIs
StatePublished - 10 Jun 2005

Keywords

  • Concentration overpotential
  • Electrochemical noise
  • Electrolyte resistance fluctuations
  • Gas cavity
  • Gas-evolving electrodes

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