Exploring a Facile Synthetic Procedure of Iron-Based Platinum Group Metal-Free Electrocatalyst for Polymer Electrolyte Fuel Cells

Abstract

The transportation sector, mainly powered by fossil fuels, is responsible for approximately 14% of all greenhouse gas emissions1. Polymer electrolyte fuel cells (PEFCs) are promising candidates for sustainable transport as they only emit water, can be refilled fast, and enable long ranges with a single refill. Their current costs and dependence on scarce materials challenge their broad implementation in heavy-duty vehicles and maritime transportation 2. Another challenge is the catalyst degradation during operation, therefore the goal of at least 35,000 lifetime hours for heavy-duty transportation is ambitious as existing fuel cell vehicles have been engineered for ca. 5,000 hours3. The state-of-the-art catalyst layers are based on platinum nanoparticles supported on carbon and global efforts have been made to develop high-activity catalysts with reduced platinum contents, including platinum alloys such as Pt-Ni4 and Pt-Co5, alternative supports such as nanotubes6, or a combination aforementioned methods. While platinum-based materials remain the most active for the oxygen reduction reaction, their elevated cost and instability during operation motivate the exploration of alternative materials.Platinum group metal (PGM)-free catalysts have gained prominence in the PEFCs field, where Fe-N-C based catalysts have shown high oxygen reduction reaction activity in acidic media7, approaching that of platinum-based catalyst layers, yet their practical application is hindered by insufficient stability under operating conditions8. Inspired by recent efforts7,8, our goal is to develop stable, active, and low-cost catalyst layers using earth-abundant materials. In this poster presentation, I will discuss my efforts in the synthesis of Fe-N-C catalysts by the incorporation of iron in a calcinated nitrogen-doped zeolitic imidazolate framework (ZIF). ZIFs are excellent supports due to their high porosity of approximately 60% and a surface area of 1600 m2/g, leading to a high density of active sites9. After the incorporation of iron, post-treatments are applied including leaching and the utilization of secondary nitrogen precursors, where efforts are made to develop non-hazardous activation approaches. The incorporation of secondary nitrogen precursors such as cyanamide have been shown to promote the formation of metal-N-C bonds and increase the performance towards the oxygen reduction reaction10,11. We employ microscopic, spectroscopic and electrochemical techniques, such as the rotating disc electrode, to correlate the catalyst composition with electrochemical performance and durability. With this work, we hope to gain an understanding of composition-structure relationships to enhance the performance of iron-based platinum-free catalysts for PEFCs. Acknowledgements SH2IPDRIVE has received funding from the Ministry of Economic Affairs and Climate Policy, RDM regulation, carried out by the Netherlands Enterprise Agency. References W.F. Lamb et al., 2021, Environmental Research Letters vol. 16.S.T. Thompson et al., 2018, Solid State Ion 319, 68–76.D.A. Cullen et al., 2021, Nature Energy vol. 6 462–474.S.I. Choi et al., 2013, Nano letters 13(7), 3420-3425.P.R. Kumar et al., 2018, Surfaces and Interfaces 12,116-123.D. Schonvogel et al., 2017, Journal of the Electrochemical Society 164(9), F995.A. Mehmood et al., 2022, Nature Catalysis 5(4), 311-323.X. Wan, and J. Shui, 2022, ACS Energy Letters 7(5), 1696-1705.J.C.Tan et al, 2010, Proceedings of the National Academy of Sciences 107(22), 9938-9943.X. Wu et al., 2022, Journal of The Electrochemical Society 169.1, 016507.N.D. Leonard et al., 2018, ACS Catalysis 8(3), 1640-1647.