Rapid and Local EIS on a Segmented Fuel Cell: A New Method for Spatial and Temporal Resolution

Abstract

A new method for acquiring temporal and spatially resolved electrochemical impedance spectroscopy data on a segmented proton exchange membrane fuel cell is developed. The cell used in this study consists of a segmented anode with 20 galvanically insulated segments. By measuring all segments simultaneously, restricting the frequency range, imposing all frequencies within one measuring task, and decoupling the acquisition and post-processing steps, we can reduce the acquisition time to 1 second. The results yield the spatial and temporal evolution of the TLM’s parameters, e.g., membrane resistance Rmem. Our results show that the temporal evolution of local Rmem strongly differs from the temporal evolution of the global Rmem. Moreover, we can see strong differences in the temporal evolution of local Rmem. The results further indicate that re-humidification after a decrease of stoichiometry appears almost instantly, while after an increase of stoichiometry it takes several minutes until the cell is dried out and equilibrated again. Furthermore, we can show, that the ratio of the 1 kHz resistance R1kHz to Rmem locally changes over time, making it an unsuitable substitute for Rmem. We therefore suggest R1kHz not to be taken as an indicator or substitute for Rmem.

Non-Invasive Measurement of Impedance Spectra Distribution in Polymer Electrolyte Fuel Cells

“…Particularly, R CT can be extracted from the impedance data even though frequencies lower than 3 Hz that provide the zero imaginary impedance are not collected. Recently, Schmitt and co-workers showed 25 that reduced frequency range sampling can be reliably used for increased temporal EIS resolution.…”

An Experimental Study of Humidity Distribution Dynamics in a Segmented PEM Fuel Cell

“…Evaluation of RH eq parameterizations under transient operation.-To enable the transient acquisition of R 0 as well as all fixed frequency resistances of interest in one dataset, we apply the so called RaLo EIS technique introduced in our previous publication. 26 We acquire EIS data in the frequency range from 10 kHz to 20 kHz every two seconds for the experimental conditions 3a and b listed in Table I. With this technique all frequencies are automatically acquired within one EIS, and no repetition of the experiment for multiple frequencies is needed.…”

“…eq A modified version of our RaLo EIS technique presented by Schmitt et al 26 been used to increase the acquisition speed for measuring R kHz 1 to 5 samples per second for all segments simultaneously. The interplay between the evolution of local RH eq and local current density has been studied, showing an alignment of their turning points.…”

“…This customized impedance data acquisition is highly flexible and can be used for rapid and local EIS (=RaLo EIS) data acquisition, which we have introduced in our latest publication. 26 By processing all 20 segments simultaneously, reducing the frequency range from 10 kHz to 20 Hz, measuring all frequencies within one acquisition task, and decoupling the acquisition and postprocessing step we are able to reduce the time for acquiring EIS on all 20 segments simultaneously to less than 1 s. Similarly, the method can be used to acquire impedance data at fixed frequencies even faster. For single frequencies, the sampling time can be reduced to ∼0.2 s. For better distinction, we will call this method RaLoff (Rapid and Local for fixed frequency) acquisition.…”

Рекуррентная Формула Для Вычисления Импеданса Катодного Каталитического Слоя В Топливном Элементе С Полимерным Электролитом

“…An alternative approach for calculation of the CCL impedance is construction of transmission line (TL) model consisting of a large number of repeated resistive and capacitive elements representing transport and kinetic processes. Recently, a TL model has been developed and used for fitting experimental impedance spectra of a segmented cell operated with neat oxygen [7]. The TL modeling usually leads to accurate results; however, some elements (processes) in the repeating TL fragment may be missing.…”