Measurements of double layer capacitance – Battery – Corrosion – Application Note 21Latest updated: August 31, 2021
In this application note, the electrical double layer of an iron electrode in acidic media is investigated. The capacitance is determined by both Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) techniques. For the EIS data, the ZFit and the pseudo capacitance tools are used to automate the capacitance calculation from an R/Q circuit.
All electrochemical processes take place at the electrode/electrolyte interface, i.e. the electrical double layer (Figure 1). Different models of this layer were stated by Helmholtz, Gouy-Chapman, Stern, or Grahame [1,2]. The structure of the double layer is similar to an electrical condenser constituted by two charged areas separated by a dielectric. The dielectric thickness corresponds to the ionic radius, i.e. 50 nm. In this note, the electrical double layer of the iron electrode in acidic conditions is investigated. In this purpose, two techniques are used to determine the value of the capacitance: the Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV).
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