Demonstrating the absence of metal ion contamination in operando PEM fuel cells utilizing unmodified stainless steel bipolar plates

• Published in: Applied energy Vol. 349; p. 121669
• Main Authors: Novalin, Timon, Eriksson, Björn, Proch, Sebastian, Bexell, Ulf, Moffatt, Claire, Westlinder, Jörgen, Lagergren, Carina, Lindbergh, Göran, Lindström, Rakel Wreland
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2023
• Subjects: Bipolar plate; Corrosion mechanism; Ionic decoupling; Proton exchange membrane fuel cell; Stainless steel passivation; Corrosion mechanism; Stainless steel passivation; Proton exchange membrane fuel cell; Bipolar plate; Ionic decoupling
• ISSN: 0306-2619; 1872-9118; 1872-9118
• DOI: 10.1016/j.apenergy.2023.121669

Using stainless steel as material for bipolar plates (BPPs) in proton exchange membrane fuel cells (PEMFCs) carries a perceived risk of corrosion and subsequent metal ion contamination of the membrane electrode assembly (MEA). However, assessments in literature on this hazard to PEMFC systems have been based on ex-situ corrosion studies, where general assumptions made on the BPP environment might not be a correct simulation of real on-site conditions. In this contribution, uncoated BPPs from stainless steel grades 304 L, 316 L and 904 L were subjected to in-situ hybrid endurance/stress testing to simulate realistic conditions in operating fuel cell systems and re-evaluate the need of additional corrosion protection. A post analysis of the plates showed no signs of surface dissolution on any of the tested samples and the concentration of iron in the MEA averaged 7 to 10 ppm for uncoated samples and 7 to 11 ppm for coated and graphitic reference tests, displaying a negligible amount of trace metals compared to critical thresholds found in literature. Contact resistance values were stable for all samples and observable changes in cell performance and voltage degradation was confirmed to be unrelated to the presence of uncoated bipolar plates. The combined effects of decoupling of bipolar plate surface potentials from electrode potentials and operational control of stable gas flow compositions to sustain stainless steel surface passivation, were identified as explanation for the experimentally observed corrosion resistance of uncoated stainless steel plates in PEMFCs. Corrosion resistance of bipolar plates stems from the interplay of three phenomena observed in operando proton exchange membrane fuel cells. [Display omitted] •Stainless steel bipolar plates without additional surface protection.•In-situ hybrid endurance/stress test simulating realistic automotive conditions.•Ex-situ analysis of plate surfaces and membrane electrode assembly.•High resistance to corrosion and metal ion contamination attested.•Interplay of ionic decoupling, stable surface potentials and sustained passivation.