Analytical concentration impedance of a transport layer

•Analytical model for concentration impedance of a transport layer (TL) is developed.•A formula for the TL concentration impedance is derived.•The characteristic frequency of TL impedance is close to the Warburg finite-length frequency. A formula for concentration (zeta-) impedance of reactant transport through a finite–length layer attached to the electrochemical electrode is derived. The static point of the Nyquist spectrum is independent of the layer transport parameters, while the peak of -Iζ is located at the frequency which is close to the Warburg finite–length frequency.