Diffusion Impedance in a Thin-Layer Cell:  Experimental and Theoretical Study on a Large-Disk Electrode

Abstract

Using an accurate thin-layer cell, the electrochemical impedance corresponding to the diffusion of ferro-cyanide ions was measured on a large-disk electrode covered by thin films of electrolyte. Experimental impedance diagrams obtained in a large frequency range (100 kHz−5 mHz) were in good agreement with those expected in the case of a spatially restricted linear diffusion impedance. For electrolyte film thicknesses lower than 100 μm, an increase of the low-frequency limit of the real part of the impedance and a decrease of the high-frequency phase angle were however observed experimentally as the electrolyte film thickness decreases. This specific behavior, in disagreement with the classical linear diffusion theory, was explained by the potential distribution existing in the thin-layer cell and was modeled using an original transmission line. In a very low-frequency range (lower than 1 mHz), an additional time constant was also evidenced. In consistency with previous work of Gabrielli et al. on microelectrodes, this feature was ascribed to the radial contribution of diffusion processes existing within a thin-layer cell.

Cathodic protection of buried steel structures: Processes occurring at the steel/soil interface during wet/dry cycles

“…This shows that the cathodic process, that is, O 2 reduction, has been affected. More precisely, this indicates that coupon WE CP1 behaves like a semi‐infinite porous electrode . This means that O 2 reduction involves, in the present case, the diffusion of O 2 inside the pores of the mineral layer covering the steel surface and its reduction on the walls of these pores.…”

“…More precisely, this indicates that coupon WE CP1 behaves like a semi-infinite porous electrode. [19][20][21] This means that O 2 reduction involves, in the present case, the diffusion of O 2 inside the pores of the mineral layer covering the steel surface and its reduction on the walls of these pores. This implies the presence of a conductive corrosion product, which is magnetite, as discussed in Section 3.4.…”

Limited Diffusion and Cell Dimensions in a Micrometer Layer of Solution: An Electrochemical Impedance Spectroscopy Study

“…The impedance behavior obtained under our experimental set‐up resulted in agreement with the limited diffusion theory for a reflecting boundary condition, with no noticeable distortion, particularly from the expected vertical line in the Nyquist plot. Other studies have considered the inclusion of a radial diffusion to explain some distortions in the impedance profile; for example, Gabrielli et al . showed that this radial diffusion is relevant in the case of microdisc electrodes, where the lateral surface is quantitatively relevant.…”

“…The impedance behavior obtained under our experimental set-up resulted in agreement with the limited diffusion theory for a reflecting boundary condition, with no noticeable distortion, particularly from the expected vertical line in the Nyquist plot. Other studies have considered the inclusion of a radial diffusion to explain some distortions in the impedance profile; [21] for example, Gabrielli et al [22] showed that this radial diffusion is relevant in the case of microdisc electrodes, where the lateral surface is quantitatively relevant. This is not our case, as scanning electron microscopic (SEM) analysis reveals that the printed layer of SPEs has a quite homogeneous width of about 10 mm ( Figure 5), so the ratio between the plane surface and the lateral printed surface is 100, and can be disregarded.…”

The Rapeseed Oil Based Organofunctional Silane for Stainless Steel Protective Coatings

“…Therefore, this way of presenting the circuit is physically meaningful. The M element represents a particular diffusion phenomena i.e., a restricted linear diffusion with reflective boundary conditions [39,40,[48][49][50][51]:…”