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Concepts for preventing metal dissolution from stainless-steel bipolar plates in PEM fuel cells
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.ORCID iD: 0000-0002-7919-8835
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.ORCID iD: 0000-0003-4770-9554
Strateg Res, Sandv Mat Technol, SE-81181 Sandviken, Sweden..
Strateg Res, Sandv Mat Technol, SE-81181 Sandviken, Sweden..
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2022 (English)In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 253, article id 115153Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier BV , 2022. Vol. 253, article id 115153
Keywords [en]
Proton exchange membrane fuel cells, Bipolar plates, Metal dissolution, Cell voltage transients, Global hydrogen starvation, Ionic (galvanic) decoupling
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-307301DOI: 10.1016/j.enconman.2021.115153ISI: 000737138800003Scopus ID: 2-s2.0-85123937646OAI: oai:DiVA.org:kth-307301DiVA, id: diva2:1630477
Note

QC 20220120

Available from: 2022-01-20 Created: 2022-01-20 Last updated: 2024-08-15Bibliographically approved
In thesis
1. Electrochemical characterization of materials for next generation polymer electrolyte fuel cells
Open this publication in new window or tab >>Electrochemical characterization of materials for next generation polymer electrolyte fuel cells
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Polymer electrolyte fuel cells occupy a key position in implementing the hydrogen economy on a global scale. However, assessments of cost, availability and sustainability of materials currently used to manufacture state-of-the-art fuel cell stacks have given cause for concern. Platinum and platinum-group metals are prohibitively expensive and of low abundance. The benchmark ion-conductive polymer NafionTM and related perfluorosulfonic acid-based polymers are difficult to synthesize and environmentally persistent to extreme degrees. Graphitic and carbon composite bipolar plates are unsuitable for mass production and have low recycling potential. In the compiled works, alternative materials were evaluated both for the acidic and alkaline variations of polymer electrolyte fuel cells. Electrochemical characterization was carried out in single cell tests with a focus on finding the limitations in terms of ohmic, charge transfer and transport resistances in the cell, through polarization and impedance measurements.

Carbon coated stainless steel bipolar plates were tested operando in a proton exchange membrane fuel cell (PEMFC) under realistic conditions based on the New European Drive Cycle. Observed trace metal contamination of the MEA was linked to metal dissolution from coating defects caused by manufacturing (Paper I). A theoretical understanding of observed metal dissolution was confirmed experimentally and a concept for preventing metal dissolution was developed for PEMFC bipolar plates (Paper II). The developed concept was extended to uncoated stainless steel bipolar plates and tested successfully for three stainless steel types in operando PEMFC (Paper III)

Anion exchange polymers based on poly(arylene piperidinium) (PAP) were tested as both membranes and ionomers in a comparative study with a commercial reference material, showing higher performance and the significance of ionomer-carbon support interactions (Paper IV). PAP-based ionomers with varying ion exchange capacities were studied to optimize electrodes in anion exchange membrane fuel cells (AEMFC). A combination of high ion exchange capacity ionomer on both cathode and anode was best performing, linked to small water transport resistance in cathode and increased kinetic contribution of the anode HOR (Paper V). The effects of modifying the catalyst layer through the introduction of crosslinked PAP particles were studied in operando AEMFCs. A positive impact on charge transfer and diffusion resistances in electrodes containing particles could be observed. (Paper VI).

Silver nanoparticles were used as catalyst material in the cathode of previously optimized membrane electrode assemblies in AEMFC. The results showed promising performance compared to platinum electrodes based on monetary and sustainability considerations, but also challenges regarding catalyst stability and detrimental silver-ionomer interactions. (Paper VII).

Abstract [sv]

Bränsleceller med polymerelektrolyt har en avgörande roll för implementering av vätgasekonomin globalt. Faktorer som kostnad, tillgänglighet och miljöpåverkan av material som för närvarande används i moderna bränsleceller är dock ett bekymmer. Platina och platinagruppmetaller är dyra och sällsynt förekommande. Den dominerande jonledande polymeren NafionTM och liknande perfluorsulfonsyra-baserade polymerer är krävande att syntetisera och svårnedbrytbara i naturen. Bipolära plattor av grafit och kolkomposit är olämpliga för massproduktion och har låg återvinningspotential. I avhandlingens sammanställda arbeten utvärderades alternativa material både för de sura (PEMFC) och de alkaliska (AEMFC) varianterna av polymerelektrolytbränsleceller. Elektrokemisk karakterisering med polarisations- och impedansmätningar genomfördes i enkelceller för att studera begränsningarna vad gäller laddningsöverföring samt ohmska och transportrelaterade förluster i cellen.

Kolbelagda bipolära plattor av rostfritt stål undersöktes in operando i en PEMFC under realistiska förhållanden baserade på en standardiserad europeisk driftcykel. Spår av metalljoner i cellkomponenterna observerades efter test och kopplades till metallupplösning från defekter orsakade vid tillverkningen (Paper I). Upplösningen visade sig bero på potentialgradienter som uppstod vid förändringar i gassammansättningen och kunde undvikas med bättre reglerade flöden (Paper II). Tre typer av rostfritt stål utan kolbeläggning jämfördes i operando PEMFC med belagda bipolära plattor Inte i något av fallen påvisades någon metalljonupplösning(Paper III).

Anjonbytarpolymerer baserade på poly(arylenpiperidinium) (PAP) undersöktes både som membran och jonomer. I en jämförande studie med ett kommersiellt Aemion-material visade PAP högre prestanda. Vidare visade studien att interaktionen mellan jonomer och bärarkol hade betydelse för prestandan (Paper IV). PAP-baserade jonomerer med varierande jonbyteskapacitet studerades för att optimera elektroder i AEMFC. En kombination med jonomer med hög jonbyteskapacitet på både katod och anod var bäst, och kopplad till litet vattentransportmotstånd i katoden och ökat kinetiskt bidrag från anodreaktionen (Paper V). Effekterna av att modifiera katalysatorskiktet genom införandet av tvärbundna PAP-partiklar studerades i operando AEMFCs. En positiv inverkan på laddningsöverföring och diffusionsmotstånd i elektroder som innehåller partiklar kunde observeras. (Paper VI). 

Slutligen användes silvernanopartiklar som katodkatalysator i AEMFC med elektroder optimerade med PAP. Resultaten visade lovande prestanda jämfört med platinaelektroder, utifrån kostnads- och hållbarhetsaspekter, men också utmaningar gällande katalysatorns stabilitet och interaktionen mellan silver och jonomer. (Paper VII).

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2023. p. 114
Series
TRITA-CBH-FOU ; 2023:59
Keywords
Polymer electrolyte fuel cells, PEMFC, AEMFC, bipolar plates, corrosion, poly(arylene piperidinium), ionomer, electrode structure, silver nanoparticles, oxygen reduction reaction, Polymerelektrolytbränsleceller, PEMFC, AEMFC, bipolära plattor, korrosion, poly(arylenpiperidinium), jonomer, elektrodstruktur, silvernanopartiklar, syrgasreduktionsreaktion
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-340853 (URN)978-91-8040-794-6 (ISBN)
Public defence
2024-01-26, F3 (Flodis), Lindstedtsvägen 26, KTH, https://kth-se.zoom.us/meeting/register/u5wlcOGuqTwiGNXzKR_gDsNo2rokLVn_pyFk, Stockholm, 10:00 (English)
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Note

QC 20231218

Available from: 2023-12-18 Created: 2023-12-15 Last updated: 2024-01-15Bibliographically approved

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Novalin, TimonEriksson, BjörnLagergren, CarinaLindbergh, GöranWreland Lindström, Rakel

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