Abstract


Porous electrodes are used in practical applications of electrochemistry. Solution resistance strongly affects impedances observed at such electrodes. Redox processes cause, in general, potential and concentration gradients inside pores. De Levie developed a porous electrode model in the absence of dc current and concentration gradient but in the presence of the potential gradient.

In the presence of dc current concentration and potential gradients appear. An analytical solution exists only when the potential gradient might be neglected. In the present lecture, four models of porous electrodes will be considered:

  1. Only dc concentration gradient exists (no dc or ac potential gradients)
  2. Dc concentration gradient with the addition of the ac solution resistance in pore
  3. Dc concentration and potential gradients exist (no ac resistance)
  4. Dc concentration and potential gradients with the addition of the ac solution resistance in pore

Simulations of the complex plane plots and comparison with the full solution (4) allow us to decide when the simplified models might be used. Models 1) and 3) produce two semicircles on the complex plane plots. Adding of the ac solution resistance in pores causes high frequency straight line at 45° followed by two(deformed) semicircles. Using de Levie's equations allows to extract the kinetic parameters for lower solution resistances.



Bio:

Prof. Lasia's photo Professor Andrzej Lasia is an Emeritus Professor from the Chemistry Department of Sherbrooke University in Quebec, Canada. He is best known for his renowned book in impedance spectroscopy "Electrochemical Impedance Spectroscopy and Its Applications". He obtained his Ph.D from the University of Warsaw, Poland, 1975 and worked at Université de Sherbrooke since 1983. During his active and then retired years his main focus was on impedance spectroscopy in connection with electrocatalysis, hydrogen adsorption, absorption and evolution, water electrolysis, porous electrodes, corrosion of metals, etc. as well as the theoretical background of impedance spectroscopy and relaxation techniques. In total, he has 162 scientific publications, over 145 conference presentations and has been a guest speaker around 100 times.