Kinetic theory of the open-circuit potential decay method for evaluation of behaviour of adsorbed intermediates

1987 ◽  
Vol 221 (1-2) ◽  
pp. 1-21 ◽  
Author(s):  
D.A. Harrington ◽  
B.E. Conway
Keyword(s):  
Kinetic Theory ◽  
Open Circuit Potential ◽  
Open Circuit ◽  
Potential Decay

A study of the electrochemical behaviour of cobalt in aqueous H2CO3/HCO3–/CO32– solutions at pH 7–9

2004 ◽  
Vol 82 (5) ◽  
pp. 583-594 ◽  
Author(s):  
Stéphan Simard ◽  
Danick Gallant
Keyword(s):  
Open Circuit Potential ◽  
Competitive Adsorption ◽  
Carbonic Acid ◽  
Acid Corrosion ◽  
Electrochemical Behaviour ◽  
Open Circuit ◽  
Corrosion Process ◽  
Rotating Disc ◽  
Solution Interface ◽  
Potential Decay

The electrochemical behaviour of a cobalt rotating electrode in H2CO3/HCO3–/CO32– aqueous solutions was investigated in the pH region from 7 to 9. The effects of H2CO3/HCO3–/CO32– concentration, pH, and the presence of phosphates as inhibitors was explored using a rotating disc electrode at 1000 rpm. Some potentiodynamic experiments indicate that for pH 8.5 and higher, carbonate and bicarbonate species play a key role on the rate of electrooxidation of cobalt. For pH lower than 8.5, the electrochemical behaviour of cobalt changes drastically and very aggressive corrosion is observed. The involvement of carbonic acid must be considered in the corrosion process of cobalt in this pH region. The study of passive film potential decay under open circuit potential and galvanostatic reduction was performed on preanodized cobalt electrodes in solutions of various compositions. These experiments indicated the phenomena occurring at the electrode–solution interface during the corrosion process. A mechanism involving competitive adsorption of different species is suggested on the basis of the experimental evidence.Key words: cobalt, bicarbonate, phosphate, carbonic acid, corrosion.

Study of a Decomposing Hydride Phase at Nickel Cathodes by Measurement of Open‐Circuit Potential Decay

1983 ◽  
Vol 130 (9) ◽  
pp. 1825-1836 ◽  
Author(s):  
B. E. Conway ◽  
H. Angerstein‐Kozlowska ◽  
M. A. Sattar ◽  
B. V. Tilak
Keyword(s):  
Open Circuit Potential ◽  
Open Circuit ◽  
Hydride Phase ◽  
Potential Decay

ON THE FORMATION OF "Ag2O3" ON SILVER ELECTRODES

1965 ◽  
Vol 43 (5) ◽  
pp. 1199-1214 ◽  
Author(s):  
E. J. Casey ◽  
W. J. Moroz
Keyword(s):  
Current Density ◽  
Open Circuit Potential ◽  
Open Circuit ◽  
Anodic Current Density ◽  
Decomposition Rates ◽  
Anodic Current ◽  
Adsorbed Species ◽  
Experimental Conditions ◽  
Potential Decay ◽  
Silver Electrodes

"Ag2O3" was examined electrochemically in eutectic KOH−H2O at −40 °C by coulombic measurements of quantities formed, open circuit potential decays, variation of potential as a function of anodic current density, and temperature coefficients of decomposition rates. It can be formed directly from Ag2O on Ag at current density (c.d.) > 15 μA/cm2, with a maximum thickness during the first oxidation cycle (25 layers, assuming a surface roughness factor of one) occurring at 65 μA/cm2. Potential decay (−∂E/∂ log t ≡ b) curves have protracted linear regions where 0.045 < b < 0.078, sometimes higher. One-tenth of a layer of adsorbed species superimposed on the higher oxide exists on the surface during O2 evolution. Reduction curves show a minimum in the potential decay of the higher oxide preceding the formation of Ag2O. The "Ag2O3" decomposes in approximately 1 h at −40 °C to either AgO or Ag2O. The activation energy for its thermal decomposition is 12.0 ± 2.0 kcal/mole. Under most experimental conditions studied the results indicated that the material is not true Ag2O3 but it is probably better described as Ag2O[O] where [O] is trapped oxygen.The evidence does point to the probable existence of a thin layer, which may be true Ag2O3, on the surface in a steady state which is maintained at high anodic current density ( > 100 μA/cm2 at −40°).

Adsorption and Oxidation of Thiosulfate on the Platinum Electrode in a Slightly Alkaline Medium

2000 ◽  
Vol 65 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Tomáš Loučka
Keyword(s):  
Alkaline Medium ◽  
Oxidation Reaction ◽  
Open Circuit Potential ◽  
Platinum Electrode ◽  
Adsorbed Layer ◽  
Open Circuit ◽  
Adsorbed Hydrogen ◽  
Oxidation Number ◽  
Hydrogen Electrode ◽  
Layer Region

The aim of this research was to study the oxidation and reduction of the adsorbed thiosulfate on the platinum electrode in a slightly alkaline medium. The adsorption was performed at the open circuit conditions. The reduction of the adsorbed layer in the hydrogen region is slower in a slightly alkaline medium than in acid. The mechanism of reduction and oxidation of adsorbed molecules is probably the same. The nonstationary currents measured in presence of thiosulfates showed that the change in the oxidation number does not take place during the adsorption in the double layer region. In the hydrogen region, thiosulfate replaces the adsorbed hydrogen while beeing reduced. Nonstationary currents at higher concentrations of thiosulfate indicate the presence of more layers on the electrode. Upon reaching higher concentrations of thiosulfate the oxidation reaction takes place between thiosulfate in solution and adsorbed product of its reduction. The open circuit potential of the platinum electrode measured in a thiosulfate solution was 0.780 and 0.783 V against the hydrogen electrode in the same solution.

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