Effect of catalyst layer defects on local membrane degradation in polymer electrolyte fuel cells

Abstract

Aiming at durability issues of fuel cells, this research is dedicated to a novel experimental approach in the analysis of local membrane degradation phenomena in polymer electrolyte fuel cells, shedding light on the potential effects of manufacturing imperfections on this process. With a comprehensive review on historical failure analysis data from field operated fuel cells, local sources of iron oxide contaminants, catalyst layer cracks, and catalyst layer delamination are considered as potential candidates for initiating or accelerating the local membrane degradation phenomena. Customized membrane electrode assemblies with artificial defects are designed, fabricated, and subjected to membrane accelerated stress tests followed by extensive post-mortem analysis. The results reveal a significant accelerating effect of iron oxide contamination on the global chemical degradation of the membrane, but dismiss local traces of iron oxide as a potential stressor for local membrane degradation. Anode and cathode catalyst layer cracks are observed to have negligible impact on the membrane degradation phenomena. Notably however, distinct evidence is found that anode catalyst layer delamination can accelerate local membrane thinning, while cathode delamination has no apparent effect. Moreover, a substantial mitigating effect for platinum residuals on the site of delamination is observed.

3D Failure Analysis of Pure Mechanical and Pure Chemical Degradation in Fuel Cell Membranes

“…3 Chemical degradation mechanisms typically involve the formation of radical chemical species, such as hydroxyl (HO•), hydroperoxyl (HOO•), and hydrogen (H•) radicals, which attack the backbone and/or side chain of the polymeric membrane molecule leading to its bond cleavage. [30][31][32] Mechanical degradation mechanisms are driven by mechanical stresses that develop within the constrained membrane due to dynamic hygrothermal conditions present during automotive duty cycles.…”

Rational Design of Ultrathin Gas Barrier Layer via Reconstruction of Hexagonal Boron Nitride Nanoflakes to Enhance the Chemical Stability of Proton Exchange Membrane Fuel Cells

“…Along with the results of OCV and FER measurements, the cross‐sectional images of the MEAs confirm that the membrane of hBN0_MEA was severely degraded after the OCV hold test for 100 h (Figure c–f). After the ASTs, all of the membranes of the MEAs did not suffer from delamination, or mechanical cracks (Figure d,f). However, the thickness of hBN0_MEA is reduced by 30% to 31.6 ± 2.3 µm, while the thickness of hBN1_MEA hardly changed even after the AST (≈44.3 µm).…”

Investigation of catalyst layer defects in catalyst-coated membrane for PEMFC application: Non-destructive method

“…Real defects and their effect on cell performance are very difficult for PEMFC manufacturers to characterize once the fuel cell stacks are installed. The topic of real defects in PEMFC electrodes is currently the subject of debate and is not fully understood …”

“…Other studies have shown that local variations in the thickness of the CCM and GDL originating during MEA fabrication can lead to cracks that function as stress concentrating points in the membrane and ultimately cause pinholes to form . Fewer studies have focused on CL defects developed due to deformation of membrane and fabrication of CCMs, that ultimately increases the electrical resistance of the CL and decreases overall performance in PEMFC.…”