Concepts for preventing metal dissolution from stainless-steel bipolar plates in PEM fuel cells. (1st February 2022)

• Record Type: Journal Article
• Authors: Novalin, Timon; Eriksson, Björn; Proch, Sebastian; Bexell, Ulf; Moffatt, Claire; Westlinder, Jörgen; Lagergren, Carina; Lindbergh, Göran; Wreland Lindström, Rakel
• Is Part Of: Energy conversion and management. Volume 253(2022)
• Publication Date: 2022-02-01
• Subjects: Proton exchange membrane fuel cells -- Bipolar plates -- Metal dissolution -- Cell voltage transients -- Global hydrogen starvation -- Ionic (galvanic) decoupling; Direct energy conversion -- Periodicals; Energy storage -- Periodicals; Energy transfer -- Periodicals; Énergie -- Conversion directe -- Périodiques; Direct energy conversion; Periodicals; 621.3105
• DOI: 10.1016/j.enconman.2021.115153
• Languages: English
• ISSNs: 0196-8904

Abstract

Graphical abstract: Highlights: Coated stain-less steel bipolar plates used in long-term single-cell tests. Ex-situ analysis of metal concentration in fuel cell components after test run. Metal oxycarbide stains on bipolar plate surface as source for metal contamination. Mitigation of dissolution by controlling surface potential through gas flows. Evidence for ionic decoupling and re-passivation of multicomponent surfaces. Abstract: The bipolar plate (BPP) is a component with vast cost-reduction potential in proton exchange membrane fuel cells (PEMFCs). Apart from mechanical and heat transfer requirements, the most desired BPP properties are high corrosion and low electrical contact resistance. In this study we confirm that due to ionic decoupling between BPPs and electrodes, the surface potentials of the BPPs remain stable even at varying operation loads. These mild potentials, in combination with low metal-ion leeching due to passive-transpassive-passive dissolution in stainless steels, suggest that low-cost carbon-coated stainless steel can readily be used as a BPP in PEMFCs. To prove this, single-fuel cell tests were carried out under realistic driving conditions, including electrochemical analysis, in-situ contact-resistance measurements, and post-mortem investigation of the membrane electrode assembly (MEA) by inductively coupled plasma trace-metal analysis, combined with electron microscopy and Auger spectroscopy of the BPPs. The results show that due to the ionic decoupling, conditions at the BPP surfaces are much less corrosive than previously thought. Furthermore, carbon-coated stainless-steel BPPs prove to be unaffected by global hydrogen starvation, which causes severe MEA degradation independent of the presence or absence of BPPs.