Diagnosis of MEA degradation under accelerated relative humidity cycling

Abstract

The objective of this work is to identify the failure mode diagnosis protocols for polymer electrolyte membrane (PEM) fuel cells with the use of accelerated testing conditions. The single cells used in this work were constructed using commercial Ion Power ® membrane electrode assemblies (MEAs) and the performance degradation was studied under accelerated dynamic reactant relative humidity (RH) conditions. The influence of RH on cell performance was investigated, and a strong dependence of degradation with respect to relative humidity was found. RH cycling was seen to not only cause the gradual decrease in performance at the beginning of cell operation, but it was also related to the rapid decline in performance observed after 330 h operation. This change in degradation rate is seen a change in the material degradation failure mechanism at this point in the operational history of the cell. The increase in cell resistance, membrane crossover, fluoride release rate and decrease in electrochemical surface area (ESA) were also observed with time, and these results were correlated to change in degradation rate. Infra-Red (IR) imaging of an aged MEA was utilized to show varying temperature profiles and outline the possibility of cracks, tears or pinholes in the membrane.

Experimental investigation of pinhole effect on MEA/cell aging in PEMFC

“…4. The nearly linear increase in current density with the potential indicates the existence of a short circuit in the MEA [6,9]. By subtracting the contribution of the internal short circuit resistance as explained in [9], the limiting current density of H 2 crossover can be obtained by following equation: …”

“…1 MPa, the open circuit voltage (OCV) decreased significantly from 0.93 to 0.22 V; on the contrary, for (P C ÀP A ) ¼ 0.1 MPa, the OCV remained unchanged. Vengatesan et al [6] and Panha et al [7] developed infra-red (IR) imaging to identify the localization of pinholes on MEA and evidenced that pinholes were formed at the inlet of the dry reactant before being propagated on the MEA surface. Computational fluid dynamics (CFD) simulation [5] showed the formation of a hot spot in the cathode catalyst layer (CL) at the site of the pinhole (Ø ¼ 0.14 mm), with local temperatures 4e5 K higher than in the surrounding area.…”

Modeling the Liquid Water Transport in the Gas Diffusion Layer for Polymer Electrolyte Membrane Fuel Cells Using a Water Path Network

“…On the one hand, the water has to be retained in the ionomer to avoid dehydration and performance loss due to low protonic conductivity. Dehydration also leads to membrane electrode assembly (MEA) degradation due to membrane thinning and pinhole formation [1,2]. On the other hand, the liquid water saturation in the gas diffusion layers (GDLs) must be low enough to sustain the gas transport from the gas channels to the active sites.…”

Microstructural and Mechanical Characterization of Catalyst Coated Membranes Subjected to In Situ Hygrothermal Fatigue

“…17 In order to evaluate the durability and diagnose potential mitigation strategies at reasonable cost and time, accelerated stress testing (AST) is generally applied via aggravating the chemical and mechanical stressors including current density, cell voltage, temperature, and RH fluctuations. 2,4,18 Open circuit voltage (OCV) 13,[18][19][20][21][22][23] and RH cycling [24][25][26][27][28][29][30] AST protocols are generally utilized to exacerbate the rate of chemical and mechanical degradation, respectively. Lai et al 24 performed in-situ humidity cycling tests on different membranes exposed to various RH swings and reported that the time-to-failure was extended as the membranes were subjected to smaller humidity swings.…”