Impedance characterization of anodized silver/silver chloride electrodes
1980; Elsevier BV; Volume: 113; Issue: 1 Linguagem: Inglês
10.1016/s0003-2670(01)85114-x
ISSN1873-4324
AutoresRathbun K. Rhodes, Richard P. Buck,
Tópico(s)Analytical Chemistry and Sensors
ResumoAbstract Impedance measurements were made on anodized silver chloride layers on silver electrodes at 293–305 K. Thicknesses calculated from coulometry ranged from 6 × 10 -5 cm to 3.6 × 10 -4 cm. Results characterized the macroscopic transport properties from 56.2 kHz to 0.0178 Hz. Bulk film specific conductivities increased to a level value of 6 × 10 -6 S cm -1 with increased thickness, and they varied with solution composition: a minimum value in 10 -3 M AgNO 3 and maxima in 10 -1 M KCl and 10 -1 M AgNO 3 . Activation energies indicated interstitial conduction in high contacting silver solutions and vacancy conduction in high contacting chloride solutions. For the thicker electrodes, a second process, probably grain boundary constriction impedances, is resolvable between 56.2 kHz and 316 Hz. At lower frequencies still, from 100 Hz to 0.316 Hz, effects of external solution diffusion are seen in dilute solutions of silver and chloride. Values for the absolute impedances and the frequency character are extremely close to theoretical predictions. At the lowest frequencies measured an additional impedance process occurs. For the thinnest electrodes the arc is semi-circular and may indicate a kinetic process or kinetics—diffusion coupling. For the thickest electrodes this arc appears like a semiinfinite diffusion process. The magnitude of this effect qualitatively explains the increased tune responses of electrodes in the most dilute solutions.
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