Kinetics of Redox Couples at Solid Electrodes III - Ferro-Ferricyanide System in Alkaline Media on Rotating Disk Electrodes of Polycristalline Perowskite Cobaltites La1-xSrxCoO3, with x = 0.2 and 0

1975 ◽  
Vol 79 (4) ◽  
pp. 323-326 ◽  
Author(s):  
H. Nguyen Cong ◽  
J. Brenet ◽  
P. Chartier
Keyword(s):  
Rotating Disk ◽  
Alkaline Media ◽  
Redox Couples ◽  
Solid Electrodes ◽  
Disk Electrodes ◽  
Kinetics Of

scholarly journals La dissolution anodique du cuivre en présence d'ions F− dans des solutions aqueuses acides

1987 ◽  
Vol 65 (9) ◽  
pp. 2109-2113 ◽  
Author(s):  
E. Potvin ◽  
M. Drogowska ◽  
H. Ménard ◽  
L. Brossard
Keyword(s):  
Anodic Dissolution ◽  
Rotating Disk ◽  
Copper Electrode ◽  
Limiting Factor ◽  
Uniform Corrosion ◽  
Acidic Solutions ◽  
Rate Of Dissolution ◽  
Disk Electrodes ◽  
Kinetics Of ◽  
Cyclic Voltamperometry

The influence of F− ions on the anodic dissolution of copper in aqueous acidic solutions (pH 1.6–6), mainly at pH 5 with 0.1 M KF, has been studied. The nature of the changes that occur on the electrode during the oxidation has been examined by cyclic voltamperometry as well as by different techniques of surface analysis (SEM, XPS, AES). To determine the mechanism of the electrochemical oxidation of copper at pH 5, studies with rotating disk electrodes have been carried out under conditions giving rise to a general dissolution of copper. At pH 1.6–6, the copper electrode dissolves uniformly, i.e., without preferential zones on the surface, when it is submitted to a potentiodynamic polarization (10 mV s−1) at potentials above 0 VECS. At slightly acidic pH (pH 5, KF0.1 M), with a sweep of potential up to +0.5 V, the oxidation of copper begins with a generalized corrosion of the electrode and it is followed by the formation of a film of Cu2O that is not passivating; as the oxidation proceeds, the current drops and the electrode becomes passivated. One model for the anodic dissolution is presented for the results obtained at pH 5. When a uniform corrosion develops on the rotating electrode, the copper is oxidized to Cu2+ ions. When ω → 0, the rate of dissolution of the electrode is limited by the diffusion of the Cu2+ ions from the electrode to the solution, whereas when ω → ∞ the process of charge transfer is the limiting factor to the kinetics of the dissolution. [Journal translation]

Kinetics of surface reactions on rotating disk electrodes

2012 ◽  
Vol 80 ◽  
pp. 326-333 ◽  
Author(s):  
Ronald Vargas ◽  
Carlos Borrás ◽  
Jorge Mostany ◽  
Benjamín R. Scharifker
Keyword(s):  
Surface Reactions ◽  
Rotating Disk ◽  
Disk Electrodes ◽  
Kinetics Of

Mineral interfacial processes in the method of induced polarization

Geophysics ◽  
1984 ◽  
Vol 49 (7) ◽  
pp. 1105-1114 ◽  
Author(s):  
James D. Klein ◽  
Tom Biegler ◽  
M.D. Horne
Keyword(s):  
Frequency Domain ◽  
Diffusion Layer ◽  
Electrode Potential ◽  
Rotation Speed ◽  
Low Frequency ◽  
Rotating Disk ◽  
Active Species ◽  
Hydrodynamic Theory ◽  
Electrode Polarization ◽  
Disk Electrodes

A phenomenological laboratory investigation has been conducted of the IP response of pyrite, chalcopyrite, and chalcocite. The technique that was used is standard in electrochemistry and employs rotating disk electrodes. The effect of rotation is to stir the electrolyte and thus to restrict the maximum distance available for diffusion of electroactive aqueous species. For high rotation speed and low excitation frequencies, the mean diffusion length exceeds the thickness of the diffusion layer. The net effect is to reduce the electrode impedance at low frequency. The thickness of the diffusion layer and thus the impedance at low frequency can be controlled by the rotation speed. Measurements using rotating disk electrodes have been conducted in both the time domain and the frequency domain. For both pyrite and chalcopyrite, the results were the same: no dependence on rotation was observed. For frequency domain measurements with chalcocite, a strong dependence on rotation was observed. The interpreted diffusion layer thickness was found to depend on rotation speed to the [Formula: see text] power, in agreement with results predicted by hydrodynamic theory. The results of this study imply that there are two physical processes responsible for electrode polarization in the IP method. For chalcocite and perhaps other related copper sulfide minerals, the probable mechanism is diffusion of copper ions in the groundwater. In case, the phenomenon is correctly described by the Warburg impedance. Chalcocite’s distinctive response is thought to be related to its forming a reversible oxidation‐reduction couple with cupric ions in solution. No other common sulfide mineral forms a reversible couple with its cations in solution. For the other minerals of this study, the lack of dependence on rotation implies that diffusion of active species in the electrolyte is not the controlling process. Possible alternate mechanisms include surface controlled processes such as surface diffusion or adsorption phenomena. Ancillary data obtained during this study indicate the interface impedance of chalcopyrite is proportional to the electrode potential which in turn can be controlled by rotation speed, electrolyte composition, or application of an external dc current or voltage. This implies that the surface concentration of active species is dependent on electrode potential.

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