Dynamic EIS

In 1997 we first used dynamic impedance (dEIS) to study Pt oxide growth doi:10.1016/S0022-0728(96)04812-7. Impedance spectra are acquired while the system is slowly changing, usually in a slow sweep voltammogram, which allows the study of surface electrochemistry under conditions that may not be accessible by conventional steady-state impedance. Our early work used lock-in amplifier methods. More recently, we have developed hardware and software to acquire and analyse impedance spectra through the muiltisine method. Ref 1 describes the hardware, and Ref 2 describes the software, algorithms, and capabilities and limitations of the method. See the main publications list for application papers.

  1. R.L. Sacci and D.A. Harrington, Dynamic Electrochemical Impedance Spectroscopy, ECS Transactions, 19 (2009) 31-42. doi:10.1149/1.3247564
  2. R.L. Sacci, F. Seland and D.A. Harrington, Dynamic Electrochemical Impedance Spectroscopy for Electrocatalytic Reactions, Electrochim. Acta., 131 (2014) 13-19. doi:10.1016/j.electacta.2014.02.120

EIS of multistep mechanisms

I have developed a general theory for the electrochemical impedance of multistep mechanisms. This theory enables prediction of the number of bends in a Bode plot for an arbitrary mechanistic scheme, without a detailed mathematical analysis, and predicts types of equivalent circuits for some classes of mechanisms.

A tutorial introduction to some aspects of the theory is given in this powerpoint presentation, which is an annotated and slightly expanded version of a talk given at the 6th International Symposium on Electrochemical Impedance Spectroscopy, Cocoa Beach, Florida, 2004. Ref 2 is more recent, covers some more general issues and is probably the best starting point.

Most recently, I have shown (ref 1) that the Nyquist plot reduces to a single semicircle when one step is rate determining.

  1. D.A. Harrington, The Rate-Determining Step in EIS, J. Electroanal. Chem.,737 (2015) 30-36. doi:10.1016/j.jelechem.2014.06.003
  2. D.A. Harrington and P. van den Driessche, Mechanism and Equivalent Circuits in EIS, Electrochim. Acta, 56 (2011) 8005-8013. doi:10.1016/j.electacta.2011.01.067
  3. D.A. Harrington and P. van den Driessche, Equivalent Circuits for Some Surface Electrochemical Mechanisms, J. Electroanal. Chem., 567 (2004) 153-166. DOI Logo
  4. J. D. Campbell, D. A. Harrington, P. van den Driessche and J. Watmough, Stability of Surface Mechanisms with Three Species and Mass-Action Kinetics, J. Math. Chem., 32 (2002) 281-301. DOI Logo
  5. D.A. Harrington and P. van den Driessche, Stability and Electrochemical Impedance of Mechanisms with a Single Adsorbed Species, J. Electroanal. Chem., 501 (2001) 222-234. DOI Logo
  6. D.A. Harrington, Stability and Inductive Behaviour in Electrochemical Impedance, Proc. of Corrosion and Prevention 2000, November 19-22, Auckland, Proceedings Volume 2000, paper 112 pp. 1-7, Australasian Corrosion Association, Brentford Square, Victoria, Australia.
  7. D.A. Harrington and P. van den Driessche, Impedance of Multistep Mechanisms: Equivalent Circuits at Equilibrium, Electrochim. Acta, 44 (1999) 4321-4329. DOI Logo
  8. D.A. Harrington, Electrochemical Impedance of Multistep Mechanisms: Mechanisms with Static Species, J. Electroanal. Chem., 449 (1998) 29-37. DOI Logo
  9. D.A. Harrington, Electrochemical Impedance of Multistep Mechanisms: A General Theory, J. Electroanal. Chem., 449 (1998) 9-28. DOI Logo
  10. D.A. Harrington, Electrochemical Impedance of Multistep Mechanisms: Mechanisms with Diffusing Species, J. Electroanal. Chem., 403 (1996) 11-24. DOI Logo
  11. D.A. Harrington and B.E. Conway. A.C. Impedance of Faradaic Reactions Involving Electrosorbed Intermediates; Part I: Kinetic Theory, Electrochim. Acta, 32 (1987) 1703-1712. doi:10.1016/0013-4686(87)80005-1

EIS for large amplitude signals

A theory for large-amplitude and second-harmonic impedances for mechanisms with a single adsorbed species was presented in Can. J. Chem., 75 (1997) 1508 doi:10.1139/v97-181, and the MAPLE worksheet is available for download.

EIS for fuel cells

We used EIS to diagnose faults in PEM fuel cell stacks running under load.

  1. J.-M. Le Canut, R. Latham, W. Mérida and D.A. Harrington, Impedance Study of Membrane Dehydration and Compression in PEM Fuel Cells, J. Power Sources, 192 (2009) 457-466. doi:10.1016/j.jpowsour.2009.03.027
  2. W. Mérida, D. Harrington, J.M. Le Canut, and G. McLean, Characterisation of Proton Exchange Membrane Fuel Cell (PEMFC) Failures via Electrochemical Impedance Spectroscopy, J. Power Sources, 161 (2006) 264–274. doi:10.1016/j.jpowsour.2006.03.067
  3. J.-M. Le Canut, R.M. Abouatallah and D.A. Harrington, Detection of Membrane Drying, Fuel Cell Flooding and Anode Catalyst Poisoning on PEMFC Stacks by Electrochemical Impedance Spectroscopy, J. Electrochem. Soc., 153 (2006) A857-A864. doi:10.1149/1.2179200