Diffusional Impedance of a Recessed Microelectrode

The impedance of the recessed microelectrode is shown in the Nyquist plot on the left; the unit of impedance is ohm ().

For a small recess depth (snapshot 1), the recessed microelectrode performs as an inlaid microdisc electrode; the diffusional impedance is similar to the impedance of a microdisc electrode. As the recess depth increases (snapshot 3), the spherical diffusion occurring at the edge of the microelectrode is reduced; the linear diffusion prevails in the recess and the diffusional impedance evolves to the Warburg impedance.

Reference

L. Murtomäki and K. Kontturi, "Electrochemical Characteristics of the Microhole ITIES," Journal of Electroanalytical Chemistry, 449(1–2), 1998 pp. 225–229. doi:10.1016/S0022-0728(98)00051-5.