The shelf-life of catalyst ink for fabricating polymer electrolyte fuel cells (PEFCs) is relevant for large-scale manufacturing with unforeseen production stops. In this study, the storage effects on the physicochemical characteristics of catalyst ink (Pt/C, Nafion, 2-propanol, water) and subsequently manufactured catalyst layers are investigated. Sedimentation analysis showed that catalyst particles are not fully stabilized by charge interaction induced by Nafion. Acetone was found to be an oxidation product, even in freshly prepared ink with platinum catalyzing the reaction. Rotating disk electrode analysis revealed that the electrochemically active surface area is, overall, minimally increased by storage, and the selectivity towards water formation (4-electron pathway) is unharmed within the first 48 h of storage. MEAs prepared from stored ink reach almost the same current density level after conditioning via potential cycling. The open-circuit voltage (OCV) increases due to increased catalyst availability. Scanning electron microscopy and mercury intrusion porosimetry showed that with increasing acetone content, the pore structure becomes finer, with a higher specific surface area. Electrochemical impedance spectroscopy revealed that this results in a more hindered mass transfer but lowered charge transfer resistance. The MEA with the highest OCV and power output and the lowest overall cell resistance was fabricated from catalyst ink stored for a duration of four weeks.

This study investigates the use of mixed ionic electronic conductors (MIECs) in ceramic structures to enhance green hydrogen storage through Chemical Looping Hydrogen (CLH) technology. A novel method integrates Yttria-stabilized zirconia (YSZ) into a ceramic foam matrix, significantly improving oxygen exchange capacity (OEC) and specific hydrogen productivity (SHP) by 30–40% with YSZ3 and 10–15% with YSZ8. Over 150 cycles, YSZ8 show the best pressure behavior in the fixed-be and doubling the storage capacity compared to conventional materials like pure ZrO₂. The study also reveals the superior cyclic stability of these materials, maintaining over 80% efficiency across numerous cycles. These advancements not only support safer, more cost-effective hydrogen storage and transportation but also demonstrate strong potential for industrial scalability, crucial for future energy systems and CO₂-neutral technologies. The structured oxygen carriers could revolutionize hydrogen storage by offering a scalable, efficient solution that meets the demands of modern energy infrastructures.

Green hydrogen is central to the energy transition, but its production often requires expensive materials and poses environmental risks due to the perfluorinated substances used in electrolysis. This study introduces a transformative approach to green hydrogen production via chemical looping, utilizing an iron-based oxygen carrier with yttrium-stabilized zirconium oxide (YSZ). A significant innovation is the replacement of Al₂O₃ with SiO₂ as an inert support pellet, enhancing process efficiency and reducing CO₂ contamination by minimizing carbon deposition by up to 700%. The major findings include achieving a remarkable hydrogen purity of 99.994% without the need for additional purification methods. The Fe-YSZ oxygen carrier possesses a significantly higher pore volume of 323 mm³/g and pore surface area of 18.3 m²/g, increasing the pore volume in the iron matrix by up to 50%, further improving efficiency. The catalytic system exhibits a unique self-cleaning effect, substantially reducing CO₂ contamination. Fe-YSZ-SiO₂ demonstrated CO₂ contamination levels below 100 ppm, which is particularly noteworthy. This research advances our understanding of chemical looping mechanisms and offers practical, sustainable solutions for green hydrogen production, highlighting the crucial synergy between support pellets and oxygen carriers. These findings underscore the potential of chemical looping hydrogen (CLH) technology for use in efficient and environmentally friendly hydrogen production, contributing to the transition to cleaner energy sources.

Mass transfer of the reactant gases, water management, thermal and electrical conductivity are all highly depending on the properties of the gas diffusion layer (GDL) in polymer electrolyte fuel cells (PEFCs). GDLs are produced in complex and energy demanding processes including high temperature graphitization and are modified using polytetrafluoroethylene (PTFE) to introduce the hydrophobicity needed to efficiently remove water [1]. PTFE is, however, negatively impacts the required electrical conductivity and is facing an uncertain future with the pending restrictions on the use of perfluoroalkyl substances (PFAS) [2], [3]. Therefore, we have investigated the use of electrically conductive polyaniline (PANI) coatings on carbon fiber substrates with modifications to increase hydrophobicity. As substrate, AvCarb carbon paper EP40 was used and PTFE treated EP40T was used as state-of-the-art reference. EP40 was coated through dip-coating or electro-coating using PANI modified with sodium dodecylbenzenesulphonate as additive to adjust hydrophobicity [4]. With this approach, we have been able to show comparable pore volumes and pore surface areas (Figure 1) through mercury porosimetry as well as comparable hydrophobic properties. References [1] A. Ozden, S. Shahgaldi, X. Li, and F. Hamdullahpur, “A review of gas diffusion layers for proton exchange membrane fuel cells—With a focus on characteristics, characterization techniques, materials and designs,” Prog. Energy Combust. Sci., vol. 74, pp. 50–102, 2019, doi: 10.1016/j.pecs.2019.05.002. [2] E. Dhanumalayan and G. M. Joshi, “Performance properties and applications of polytetrafluoroethylene (PTFE)—a review,” Adv. Compos. Hybrid Mater., vol. 1, no. 2, pp. 247–268, Jun. 2018, doi: 10.1007/s42114-018-0023-8. [3] ECHA/NR/23/04, “ECHA publishes PFAS restriction proposal,” 2023. https://echa.europa.eu/-/echa-publishes-pfas-restriction-proposal (accessed Mar. 27, 2023). [4] F. Tritscher, A. Mularczyk, A. Forner-Cuenca, V. Hacker, and M. Bodner, “Surfactant doped polyaniline coatings for functionalized gas diffusion layers in low temperature fuel cells.”, under review Figure 1: Mercury porosimetry measurements for the bare substrate, the state-of-the-art PTFE treated substrate, as well as hydrophobic PANI coated samples, prepared using dip-coating and electro-coating. Figure 1