Analysis of gas transport phenomena in a polymer electrolyte fuel cell by electrochemical pressure impedance spectroscopy

Electrochemical Pressure Impedance Spectroscopy for Polymer Electrolyte Membrane Fuel Cells: Signal Interpretation

“…Furthermore, they measured a strong increase of the maximum magnitude for a decrease of the oxygen stoichiometry, which they interpreted as oxygen diffusion becoming rate-controlling for a higher oxygen depletion. 14 The same trend for a variation of oxygen stoichiometry was observed by Zhang et al, 19 who attributed the increase of the magnitude to the decrease of the oxygen concentration and hence an increase of the "mass transport impedance." Furthermore, Shirsath et al measured an increase of the maximum magnitude for the cell operation under flooding conditions 15 and for the replacement of the gas diffusion layer (GDL) from a product with microporous layer (MPL) to one without.…”

“…Engebretsen et al 13 used a loudspeaker for the pressure excitation, which allowed them to measure spectra up to 100 Hz, but the spectra were subject to considerable noise. Shirsath et al [14][15][16][17][18] and Zhang et al 19 used a more accurate pressure controller for the pressure excitation, which led to a cleaner signal, albeit in a reduced frequency range below 1 Hz and 0.1 Hz, respectively. In addition to EPIS, similar new characterization methods are currently investigated which are based on the same basic idea but differ in their approach.…”

“…In the case of EPIS, Shirsath et al [14][15][16][17] and Zhang et al 19 obtained typical common features for the operation with air as the cathode gas feed. Figure 1 shows exemplary EPI spectra in the Bode representation taken from our previous combined experimental and modeling study.…”

“…In the extended frequency range of the simulations above 1 Hz, the magnitude shows a decrease (FOI 5) towards zero, qualitatively consistent with the experimental results of Engebretsen et al that extended up to 100 Hz. 13 Shirsath et al 14 attributed the large magnitude (FOI 3) and the strongly negative phase shifts (FOI 4) to the diffusion of oxygen. This hypothesis was based on their EPIS experiments with a change of the cathode gas feed composition from air to pure oxygen, 16 for which the increase of magnitude and decrease of phase shift with frequency was less pronounced.…”

Molecular-Level Control over Oxygen Transport and Catalyst–Ionomer Interaction by Designing Cis–Trans Isomeric Ionomers

“…In the equivalent circuit, R Ω represents the total ohmic resistance of the cell (mainly caused by the ionic resistance of the AEM). R Ct usually describes the interfacial charge transfer resistance of the MEA. , The two MEAs exhibited similar ohmic resistance because they were equipped with the same AEM (which can also be observed from the high-frequency resistances (HFR) curves in Figure a). However, the interfacial resistances of the two MEAs are quite different, especially at low RH.…”