Dealloying below the critical potential

K. Wagner, S. R. Brankovic, N. Dimitrov, Karl Sieradzki

Research output: Contribution to journalArticle

69 Citations (Scopus)

Abstract

Conventionally, the critical potential represents the potential marking the onset of bulk dealloying. The current density below the critical potential is only weakly dependent on potential, and the physical processes responsible for this passive-like behavior are poorly understood. In situ scanning tunneling microscopy was used to study the nature of the surface morphology which develops at potentials less than the critical potential. At fixed potential, the time-dependent evolution of the surface morphology was correlated with the observed current decay. This allowed us to identify and model the physical processes which control the current decay. We find two general regimes of power, law behavior in the current decay corresponding to exhaustion of an activation-controlled dissolution process (t-1) and the operation of one of three mechanisms of surface mass-transport control (t-5/8, t-1/2, and t-1/4). Potential-pulsing experiments were performed in order to examine the effect of a "blocking" noble-metal layer on the nucleation and growth of the porous structure associated with bulk dealloying. These results were analyzed using a Johnson-Mehl-Avrami analysis. The Avrami exponents found were fractional and in the range of 1.25 to 1.8. The fractional exponents were interpreted in terms of the fractal dimension characterizing the initial stages of porosity formation during bulk dealloying.

Original languageEnglish (US)
Pages (from-to)3545-3555
Number of pages11
JournalJournal of the Electrochemical Society
Volume144
Issue number10
StatePublished - Oct 1997

Fingerprint

Surface morphology
Scanning tunneling microscopy
Fractal dimension
Precious metals
Process control
Dissolution
Nucleation
Current density
Mass transfer
Porosity
Chemical activation
decay
Experiments
exponents
exhaustion
noble metals
marking
scanning tunneling microscopy
fractals
dissolving

ASJC Scopus subject areas

  • Electrochemistry
  • Surfaces, Coatings and Films
  • Surfaces and Interfaces

Cite this

Wagner, K., Brankovic, S. R., Dimitrov, N., & Sieradzki, K. (1997). Dealloying below the critical potential. Journal of the Electrochemical Society, 144(10), 3545-3555.

Dealloying below the critical potential. / Wagner, K.; Brankovic, S. R.; Dimitrov, N.; Sieradzki, Karl.

In: Journal of the Electrochemical Society, Vol. 144, No. 10, 10.1997, p. 3545-3555.

Research output: Contribution to journalArticle

Wagner, K, Brankovic, SR, Dimitrov, N & Sieradzki, K 1997, 'Dealloying below the critical potential', Journal of the Electrochemical Society, vol. 144, no. 10, pp. 3545-3555.
Wagner K, Brankovic SR, Dimitrov N, Sieradzki K. Dealloying below the critical potential. Journal of the Electrochemical Society. 1997 Oct;144(10):3545-3555.
Wagner, K. ; Brankovic, S. R. ; Dimitrov, N. ; Sieradzki, Karl. / Dealloying below the critical potential. In: Journal of the Electrochemical Society. 1997 ; Vol. 144, No. 10. pp. 3545-3555.
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