Electrochemical impedance spectroscopy frequency region

Figure 6.24. Expansion of the high-frequency region of Figure 5.4 [24]. (Reprinted from Electrochimica Acta, 50(12), Easton EB, Pickup PG. An electrochemical impedance spectroscopy study of fuel cell electrodes. Electrochim Acta, 2469-74, 2005, with permission from Elsevier and the authors.)...

Electrochemical impedance spectroscopy (EIS) analysis was performed in 0.5 M NaCl solution at room temperature, using a Gamry REF 600 potentiostat. A three-electrode cell was employed, with the variously treated AA3105 aluminium alloys as the working electrode, a saturated calomel reference electrode and a platinum wire counter electrode. Before EIS analysis, the open-circuit potential of the specimen was continuously monitored from immersion in the electrolyte for 30 min. The EIS data were acquired over the frequency region of 1 MHz to 0.001 Hz at 7.13 points per... 

The impedance spectroscopy is most promising for electrochemical in situ characterization. Many papers have been devoted to the AB5 type MH electrode impedance analysis [15-17]. Prepared pellets with different additives were used for electrochemical measurements and comparing. Experimental data are typically represented by one to three semicircles with a tail at low frequencies. These could be described to the complex structure of the MH electrode, both a chemical structure and porosity [18, 19] and it is also related to the contact between a binder and alloy particles [20]. The author thinks that it is independent from the used electrolyte, the mass of the electrode powder and the preparing procedure of electrode. However, in our case the data accuracy at high frequencies is lower in comparison with the medium frequency region. In the case, the dependence on investigated parameters is small. In Figures 3-5, the electrochemical impedance data are shown as a function of applied potential (1 = -0.35V, 2 = -0.50V and 3 = -0.75V). 

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