CRUZ-MANZO, S., CHEN, R. and RAMA, P., 2012. Inductive effect on the fuel cell cathode impedance spectrum at high frequencies. Journal of Fuel Cell Science and Technology, 9(5), 051002, 8pp.
The high frequency electrochemical impedance measurements with positive imaginary
components in the impedance complex plot of a polymer electrolyte fuel cell (PEFC) are
attributable to the inductance of the electrical cables of the measurement system. This
study demonstrates that the inductive effect of the electrical cables deforms the high frequency
region of the cathode impedance spectrum and as such leads to an erroneous
interpretation of the electrochemical mechanisms in the cathode catalyst layer (CCL).
This study is divided into a theoretical analysis and an experimental analysis. In the theoretical
analysis a validated model that accounts for the impedance spectrum of the CCL
as reported in the authors’ previous study is applied with experimental impedance data
reported in the literature. The results show that the ionic resistance of the CCL electrolyte
which skews the oxygen reduction reaction (ORR) current distribution toward the
membrane interface is masked in the cathode impedance spectrum by the inductive component.
In the experimental analysis cathode experimental impedance spectra were
obtained through a three-electrode configuration in the measurement system and with
two different electrical cables connected between the electronic load and the PEFC. The
results agree with the theoretical analysis and also show that the property of causality in
the Kramers-Kronig mathematical relations for electrochemical impedance spectroscopy
(EIS) measurements is violated by the external inductance of the measurement cables.
Therefore the experimental data presenting inductance at high frequencies do not represent
the physics and chemistry of the PEFC. The study demonstrates that a realistic
understanding of factors governing EIS measurements can only be gained by applying
fundamental modeling which accounts for underlying electrochemical phenomena and
experimental observations in a complementary manner.
The authors thank the Mexican National Council for Science
and Technology (CONACYT) for the sponsorship of the Ph.D.
research study of S. Cruz-Manzo (Grant No. 183195).