Impedance Study on Estimating Electrochemical Mechanisms in a Polymer Electrolyte Fuel Cell During Gradual Water Accumulation

Abstract

In this study, the change of electrochemical parameters during the gradual water accumulation of a polymer electrolyte fuel cell (PEFC) are estimated using electrochemical impedance spectroscopy (EIS) measurements and an impedance model based on electrode theory during a two‐step oxygen reduction reaction (ORR). EIS measurements were carried out in a 5 cm2 H2/O2 PEFC operated under a dead‐ended configuration of the gas reactants and during gradual accumulation of water. Kramers‐Kronig evaluation demonstrated that the EIS measurements comply with stability and linearity properties and the inductive loops featured at low frequencies are attributed to electrochemical mechanisms within the PEFC and not to instability during gradual water accumulation. The impedance model has been reported in a previous study and simulates inductive loops at low frequencies which are attributed to platinum oxide formation during the ORR. The estimated parameters obtained from this EIS‐modeling analysis can provide an insight into the decrease in PEFC performance during flooding conditions. A further qualitative analysis considering the effect of long‐term water accumulation on the oxygen‐reduction charge transfer resistance is discussed. It is possible to have an insight into the physical mechanisms of the PEFC, by combining different experimental techniques and fundamental theory in a complimentary manner.

Electrochemically induced catalytic adsorption sites in spent lithium-ion battery cathodes for high-rate vanadium redox flow batteries

“…The inductive loop showed that the electrochemical reaction was not complete, and the intermediates remained on the electrode surface. 65–67…”

Superionic Conduction in One-Dimensional Nanostructures

“…Over this frequency range, resistance (Re­( Z )) and reactance (−Im­( Z )) were recorded and graphed as Nyquist plots: −Im­( Z ) vs Re­( Z ). All Nyquist plots show positive values of Im­( Z ) at high frequencies, which is attributed to stray inductance from electrical wiring in the measurement setup . From the measured impedance, the total conductivity was determined by the equation σ = L / RA where L is the pellet thickness measured by digital calipers after the measurement, R is the resistance obtained from the x -intercept in Nyquist plots, and A is the cross-sectional area of the pellet, which was based on the inner diameter of the die used for pellet pressing.…”

“…All Nyquist plots show positive values of Im(Z) at high frequencies, which is attributed to stray inductance from electrical wiring in the measurement setup. 48 From the measured impedance, the total conductivity was determined by the equation σ = L/RA where L is the pellet thickness measured by digital calipers after the measurement, R is the resistance obtained from the x-intercept in Nyquist plots, and A is the cross-sectional area of the pellet, which was based on the inner diameter of the die used for pellet pressing. The Hebb−Wagner polarization technique was employed to measure the contribution of Cu + to the total electrical conductivity.…”

Further Understanding of Uncertainties in the Impedance Spectrum of the Polymer Electrolyte Fuel Cell due to Inductive Effects and Oxygen Diffusion Time Constant

“…9 to predict the inductive loop at low frequencies. In addition, parameters from theoretical relations reported in the literature and through a graphical interpretation of the complex plot were considered [50]. Noting that the inductor element was neglected ( = 0 in Eq.…”