Anode aging in polymer electrolyte membrane fuel Cells I: Anode monitoring by ElectroChemical impedance spectroscopy

Oxygen Transport Impedance in a Polymer Electrolyte Membrane Fuel Cell Equivalent Electrical Circuit

“…Note that the anode was also considered in the impedance models to get a better fit between theoretical and experimental data. This choice was consistent with one of our previous work where we had observed a degradation of the anode [14]. However, in the absence of anode degradation, similar or perhaps better fits may have been obtained using a TLM model for the CCL, i.e.…”

“…The above equation is obtained using 𝑅 𝑐𝑡 = 𝑏 𝑐 〈𝑗 𝑐𝑒𝑙𝑙 〉 𝑡 ⁄ ; 𝑅 𝑑 = 𝑏 𝑐 𝛿 4𝐹𝐷 𝑒𝑓𝑓 〈𝐶 𝑂 2 (0)〉 𝑡 ⁄ and 𝜏 𝑑 = 𝛿² 𝐷 𝑒𝑓𝑓 ⁄ [14], with jcell the current density (0.5 A/cm² in this case), F the Faraday constant (96 485 C.mol -1 ) and 〈𝐶 𝑂 2 (𝑂)〉 𝑡 the oxygen concentration at the GDL/channel interface, assessed by solving Fick's equation in steadystate [17]:…”

“…In addition to its simplified geometry, another particularity of this cell lies in the current collection, which is done independently on 20 electrically isolated segments along the channel length: this allows the measurement of the local impedance on each of these segments. A more complete description of this instrumented and segmented cell can be found in our previous work, see for instance [14]. Impedance data were measured in galvanostatic mode, -mostly at 0.5 A.cm -2 -with a perturbation amplitude of 10% for frequencies ranging from 10 mHz to 10 kHz, and with 10 points per decade.…”

Anode defects’ propagation in polymer electrolyte membrane fuel cells

“…These degradation mechanisms strongly depends on the operating conditions: high temperature and relative humidity (RH) are generally considered as aggravating factors for degradation [ [14][15][16][17][18][19] ]. However, although most of the works focus on the cathode, strong degradation at the anode was also evidenced under specific conditions, such as start-up and shut-down cycling, wet-dry cycling, potential cycling, and anode flooding [ [20][21][22][23]. Many studies have also shown that the use of reformed hydrogen containing varying amounts of carbon monoxide (CO) has a harmful effect on the anode [ 21,[24][25][26][27][28] ], the damages being often reversible.…”

“…Nevertheless, such membrane degradations in the regions where the cathode overlaps the anode were also confirmed by Ohma et al [ 40 ] in OCV conditions. For these reasons, it is reasonable to suspect that similar degradation mechanisms may occur anywhere in the cell when the anode CL is missing (due to possible imperfect manufacturing processes) or when it is strongly degraded; all the more so since anode defects or anode degradation have only a small impact on FC performances [ 22 ], so that they can remain undetected for rather long durations.…”