(87j) Ageing Effects of Catalyst Ink for Polymer Electrolyte Membrane Fuel Cells

The major contribution, about 90 %, of the energy demand in the transport sector is up to date provided by petroleum products [1]. A viable way to reduce greenhouse gas emissions in this sector is to use hydrogen as a fuel for polymer electrolyte membrane fuel cell (PEMFC) vehicles. The widespread commercialisation of fuel cell electric vehicles demands an increase in reliability and durability as well as a reduction in costs [2,3]. The performance-determining core unit of a PEMFC, the membrane electrode assembly, consists of a polymer electrolyte membrane which is covered with anodic and cathodic catalyst layers (CLs) on both sites, respectively. CLs are formed by applying catalyst inks (CI) onto the PEM, with different application methods, such as spray coating or inkjet printing. Most commonly, the CI consists of a catalyst (e.g., platinum), an ionomer as binder, as well as an alcohol-water mixture as solvent. The electrochemical reactions take place in the CI and consequently the CI is vital for the performance of a PEMFC. Unfortunately, ageing effects during CI storage can cause activity losses and performance degradation.

In this work, we demonstrate CI ageing degradation effects under various aspects over a long storage time of up to three weeks. The composition of the CI (Pt/C, Nafion, isopropanol, water) is kept constant for all measurements and based on in-house experience. Sedimentation studies reveal a significant change in concentration of the components over time despite the overall adequate stability of dispersion. Degradation products formed by the oxidation of isopropanol are qualified and quantified. Results show their non-negligible presence even in freshly prepared CI. Half and fuel cell measurements are used to determine the effect of storage on the catalytic activity and hence, the cell performance. Results could be used for considerations about CI preparation and storage in small and large-scale PEMFC production e.g., for the reduction of waste or increased PEMFC performance.

References

1. S. Energy Information Administration. Use of energy explained: Energy use for transportation. 2021. URL: https://www.eia.gov/energyexplained/use-of-energy/transportation.php (accessed: 11/04/2022)

2. Iain Staffell et al. “The role of hydrogen and fuel cells in the global energy system”. In: Energy & Environmental Science 12 (2019), pp. 463 – 491. DOI: 1039/C8EE01157E

3. Gregory Trencher. “Strategies to accelerate the production and diffusion of fuel cell electric vehicles: Experiences from California”. In: Energy Reports 6 (2020), pp. 2503 - 2519. DOI: 1016/j.egyr.2020.09.008