Investigation of PEMFC Cathode Rf-Dependent Performance Losses for Voltage Cycling and Start-up Accelerated Stress Tests
Authors: Hnyk Franziska Carmen , Astudillo Leonardo Isaias , Hughes Sydney , Gasteiger Hubert Andreas 
Published: December 2024

In order to replace internal combustion engines in the heavy-duty (HD) transportation sector, proton exchange membrane fuel cells (PEMFCs) require extended operating hours with minimal performance loss.[1] During research and development, the fuel cell stack performance loss for >30,000 hours of operation can be estimated by tailored accelerated stress tests (ASTs) that induce typical degradation modes which can be tested in small active area single-cells. Two of the main cathode catalyst layer degradation modes resulting in a reduced electrochemical surface area are Pt degradation by load/voltage cycling (VC) and carbon support degradation by start-up (SU).
VC ASTs induce performance losses by decreasing the roughness factor (rf) of the cathode catalyst, due to Pt particle growth through the mechanism of Ostwald ripening and by loss of the Pt into the ionomer/membrane phase.[2] For small cathode rfs, an increase in O2 transport resistance leads to a severe drop in performance. As shown in previous studies, during VC ASTs a characteristic correlation between cathode rf and H2/air performance loss can be found for a given membrane electrode assembly (MEA).[3] However, performance losses during SU ASTs originate from a combination of Pt degradation and carbon corrosion,[4,5] which is affecting this characteristic correlation.
This study will focus on HD relevant VC and SU protocols to mimic cathode catalyst layer degradation during PEMFC operation. For the SU AST, an adapted protocol from Bisello et al.
[5] is applied to an MEA with a Pt/C cathode catalyst in a 50cm2 single-cell setup. The rf-dependence of the H2/Air performance is reevaluated for the SU protocol, comparing it to the VC AST. Furthermore, VC and SU protocols are combined to get further insights into the design of combined AST protocols and the resulting lifetime assessment of cathode catalyst layers undergoing mixed modes of degradation.

References

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Acknowledgement

We gratefully acknowledge financial support from the Fuel Cells and Hydrogen 2 Joint Undertaking (JU) under the MORELife grant agreement 101007170 that enabled us to conduct these studies. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and Hydrogen Europe and Hydrogen Europe Research.