The electrical contact resistance is a key parameter for optimising both the bipolar plate of the polymer electrolyte membrane fuel cell (PEMFC) and the electrical contact of the power terminal of the stack. The contact resistance is affected by the conductivity, roughness, and hardness of the two contacting surfaces. Here, new, application-specific contact resistance measurement methods are proposed for both the stack power terminal, and the bipolar plate. The proposed methods are compared to methods from references as well as standards, and it is concluded that the uncertainty of the measurements can be reduced by changing the measurement setup, and that the influence of probe resistance on measurement results can be eliminated. Furthermore, the effect of different accelerated durability tests on the contact resistance of the power terminal is examined both on test coupons and on a prototype screw connection with an electroless NiP and an electroplated NiSn coatings. As expected, the NiSn coupons gives lower contact resistance after ageing as compared to the NiP. However, the increase in contact resistance seen on coupons after ageing is not observed on the prototype screw connection.

Proton exchange membrane fuel cells (PEMFCs) are used to convert hydrogen and oxygen to electricity, heat, and water. There are no greenhouse gas emissions, given that the hydrogen is produced from renewable sources, such as water electrolysis from wind, hydro or solar energy. PEMFCs can be found on the commercial market today, predominantly in applications such as forklifts, passenger cars and combined heat and power units. The PEMFC is a new technology, and there are hurdles to overcome, mainly with regard to price and durability.

In this work, two PEMFC components are the main focus: the bipolar plate and the catalyst. For the bipolar plate, the effect of defects from fabrication is investigated to further understand the critical factors for corrosion and how to avoid it. Droplets from laser cutting and cracks in the coating due to the forming of pre-coated plates are both identified as possible sources of corrosion. However, by correct design, both can be avoided or made less critical. Laser welding stainless steel 304 is, on the other hand, found not to be a source of corrosion under simulated PEMFC bipolar plate conditions. Furthermore, tailoring the properties of a multicomponent alloy coating by additions of Ta and W is explored to stabilise the coating at higher potentials in the acidic environment of the PEMFC. Ta is found to achieve a protective passive layer at a lower concentration than W. However, it does significantly increase the interfacial contact resistance. One-step synthesis of a ternary alloy by electrodeposition is studied for the catalyst to allow for facile screening of new alloy compositions, both in- and ex-situ. The ternary alloy gives comparable results to the binary alloy even at lower Pt content.

As the PEMFC has entered the commercial market relatively quickly, there is a lack of standardised tests, both on the component and system level. The procedure for testing the interfacial contact resistance of the bipolar plate is studied in detail, and the methodology is further developed to ensure reliable and comparable results.

Protonledande polymermembranbränsleceller (PEMFCs) används för att omvandla vätgas och syrgas till elektricitet, värme och vatten. Om vätgasen produceras på ett förnybart sätt, till exempel genom vattenelektrolys driven med sol, vind eller vattenkraft, sker det inga utsläpp av växthusgaser. Redan idag finns PEMFCs på den kommersiella marknaden. Huvudsakligen används de i applikationer som gaffeltruckar, personbilar och kraftvärmeapplikationer. Eftersom PEMFCs är en relativt ny teknik, finns det fortfarande ett behov för utveckling, speciellt när det kommer till kostnad och livslängd.

Två PEMFC komponenter har varit huvudfokus för detta arbete: den bipolära plattan och katalysatorn. För den bipolära plattan studeras effekten av defekter från produktionen på korrosionsbeständigheten. Både droppar av smält metall från laserskärning och sprickor i beläggningen från formning av förbelagd plåt kan initiera korrosion på den bipolära plattan. Dock, kan båda defekterna undvikas vid korrekt design av plattan. Däremot visar det sig att lasersvetsar i rostfritt stål 304 utan beläggning inte initierar korrosion i ett simulerat PEMFC-miljö. I tillägg utforskas möjligheten att utvidga det passiva området för en multikomponentlegering genom tillsatser av Ta och W. Ta bildar ett stabilt passivskikt vid lägre halter jämfört med W, dock ökar kontaktresistansen signifikant. För katalysatorn studeras elektroplätering av en ternär legering direkt på gasdiffusionsskiktet för enkel screening av nya legeringar för katalysatorn. Den ternära legeringen ger jämförbar prestanda med den binära, även vid låga Pt halter.

Allt eftersom PEMFC har kommersialiserats ökar fokuset på utveckling av standardiserade prov, både på komponent och systemnivå. Metodologin för att mäta kontaktresistansen för bipolära plattor vidareutvecklas i detta arbete för att säkra pålitliga och repeterbara mätningar.

This study provides principles for designing new corrosion resistant high entropy alloys. The theoretical framework is a percolation model developed by Newman and Sieradzki that predicts the ability of an alloy to passivate, i.e., to form a protective surface oxide, based on its composition. Here, their model is applied to more complex materials than previously, namely amorphous CrFeNiTa and CrFeNiW alloys. Furthermore, the model describes a more complex passivation process: reforming the oxide layer above the transpassive potential of Cr. The model is used to predict the lowest concentration of Ta or W required to extend the passive region, yielding 11–14 at% Ta and 14–17 at% W. For CrFeNiTa, experiments reveal a threshold value of 13–15 at% Ta, which agrees with the prediction. For CrFeNiW, the experimentally determined threshold value is 37–45 at% W, far above the predicted value. Further investigations explore why the percolation model fails to describe the CrFeNiW system; key factors are the higher nobility and the pH sensitivity of W. These results demonstrate some limitations of the percolation model and offer complementary passivation criteria, while providing a design route for combining the properties of the 3d transition metal and refractory metal groups.

Proton exchange membrane fuel cells (PEMFCs) are an important alternative to fossil fuels and a complement to batteries for the electrification of vehicles. However, their high cost obstructs commercialization, and the catalyst material, including its synthesis, constitutes one of the major cost components. In this work, Pt–Ni and Pt–Ni–Mo(O) nanoparticles (NPs) of varying composition have been synthesized in a single step by pulse electrodeposition onto a PEMFC's gas diffusion layer. The proposed synthesis route combines NP synthesis and their fixation onto the microporous carbon layer in a single step. Both Pt–Ni and Pt–Ni–Mo(O) catalysts exhibit extremely high mass activities at oxygen reduction reaction (ORR) with very low Pt loadings of around 4 μg/cm2 due to the favorable distribution of NPs in contact with the proton exchange membrane. Particle sizes of 40–50 nm and 40–80 nm were obtained for Pt–Ni and Pt–Ni–Mo(O) systems, respectively. The highest ORR mass activities were found for Pt67Ni33 and Pt66Ni32–MoOx NPs. The feasibility of a single-step electrodeposition of Pt–Ni–Mo(O) NPs was successfully demonstrated; however, the ternary NPs are of more amorphous nature in contrast to the crystalline, binary Pt–Ni particles, due to the oxidized state of Mo. Nevertheless, despite their heterogeneous nature, the ternary NPs show homogeneous behavior even on a microscopic scale.

As part of the global work towards reducing CO2 emissions, all vehicles needs to be electrified, or fueled by green fuels. Batteries have already revolutionised the car market, but fuel cells are believed to be a key energy conversion system to be able to electrify also heavy duty vehicles. The type of fuel cell commercially available for vehicles today is the polymer electrolyte membrane fuel cell (PEMFC), but for it to be able to take a larger market share, the cost must be reduced while sufficient lifetime is ensured.

The PEMFC is a system containing several components, made of different materials including the polymer membrane, noble metal catalyst particles, and metallic bipolar plate. The combination of different materials exposed to elevated temperature, high humidity and low pH make the PEMFC components susceptible to corrosion and degradation.

The noble metal catalyst is one of the major contributors to the high cost. In this work, the latest research on new catalyst materials for PEMFCs are overviewed. Furthermore, electrodeposition as a simple synthesis route to test different Pt-alloys for the cathode catalyst in the fuel cell is explored by synthesis of PtNi and PtNiMo. The gas diffusion layer of the PEMFC is used as substrate to reduce the number of steps to form the membrane electrode assembly.

In addition to cheaper and more durable materials, understanding of how the materials degrade, and how the degradation affects the other components is crucial to ensure a long lifetime. Finding reliable test methods to validate the lifetime of the final system is necessary to make fuel cell a trusted technology for vehicles, with predictable performance.

In this work, commercial flow plates are studied, to see the effect of different load cycles and relative humidities on the corrosion of the plate. Defects originating from production is observed, and the effect of these defects on the corrosion is further analysed. Suggestions are given on how the design and production of bipolar plates should be made to reduce the risk of corrosion in the PEMFC.

Som en del av det globala arbetet med at reducera utsläppen av koldioxid måste alla fordon elektrifieras eller tankas med förnybart bränsle. Batterier har redan revolutionerat bilmarknaden, men bränsleceller är en viktig pusselbit för att också elektrifiera tunga fordon. Den typen av bränsleceller för fordon som finns tillgänglig på den kommersiella marknaden i dag är polymerelektrolytbränslecellen (PEMFC). För att PEMFC skall ta en större marknadsandel måste kostnaderna minskas och livslängden förlängas.

PEMFC består av ett antal komponenter gjorda av olika material, bland annat polymer membran, ädelmetallkatalysator, och metalliska bipolära plattor. Kombinationen av olika material i tillägg till den höga temperaturen, hög fuktighet och låg pH gör att materialen i bränslecellen är utsatta för korrosion.

Ädelmetallkatalysatorn är en av de kostdrivande komponenterna i bränslecellen. I denna studien presenteras en översikt över framstegen inom katalysatormaterial för PEM bränsleceller de senaste två åren. Sedan studeras elektroplätering som en enkel produktionsmetod för nanopartiklar av platina legeringar. Möjligheten att simultant plätera fler metaller, och att använda gasdiffutions-skiktet från bränslecellen som substrat för att reducera antal produktionsteg och därmed reducera kostnader, undersöks. Det möjliggör också snabb testning av olika legeringar för att identifiera den optimala sammansättningen med hög prestanda, lång livslängd och lite platina.

I tillägg till att ta fram billigare och tåliga material är det viktigt att förstå hur materialen degraderar och hur degraderingen av ett material påverkar de andra komponenterna. Med den kunskapen kan man utveckla accelererade testmetoder för att bedöma livslängden av hela bränslecellen. Validerade testmetoder är viktigt för att styrka förtroendet till nya teknologier.

I denna studien fokuseras det också på korrosion av bipolära plattor, och hur olika lastcykler och fuktnivåer som kan bli applicerad vid accelererad testning påverkar korrosionen. Också effekten av defekter från tillverkningen i den skyddande beläggningen analyseras med hänsyn till korrosion, för att ge mer insikt i hur bipolära plattor kan designas och produceras för att minska korrosionen.

Research on fuel cell technology is constantly gaining importance, while global emission requirements are becoming more and more restrictive. For environmentally neutral proton exchange membrane fuel cells (PEMFCs) to become a competitive technology, sustainable infrastructures need to be established. One of the main showstoppers is the utilization of the rare and therefore costly precious metal Pt as the key element in the electrocatalysis of hydrogen and oxygen. A huge amount of research is done on immensely reducing or even replacing Pt for future PEMFC technology. In this research update, the progress on oxygen reduction reaction catalysts in acidic media over the past two years is reviewed, with special attention to their durability.