Advanced Catalysts for PEM Water Electrolyzers, Fabricated By Reactive Spray Deposition Technology: Study of the Degradation Mechanisms in the Catalysts’ Layers By in-Situ and Ex-Situ Synchrotron X-Ray Absorption Spectroscopy

Abstract

Development of novel and improved catalysts and membrane electrode assemblies (MEAs) for proton exchange membrane (PEM) based energy conversion devices is of crucial importance for widespread application of the PEM fuel cells (FCs) and water electrolyzers (WEs). These PEM based devices are critical for the Hydrogen Economy (HE) implementation. The HE is the economy of the near future and is the only viable alternative to the current fossil fuel-based economy. This future green economy will eliminate the greenhouse gas emissions and stop the imminent global warming and climate change. Currently, the main challenges that the state-of-the-art MEAs for PEMWEs are facing are: (i) high cost because of the high platinum group metals (PGM) loadings in their catalysts layers and time consuming and expensive multi-step fabrication processes; and (ii) poor durability caused by the instability of the catalysts and the materials [1, 2].The reactive spray deposition technology (RSDT), developed at UConn, is a novel methodology for fabrication of advanced MEAs for PEMFCs and PEMWEs [3-5]. The RSDT is a flame assisted method [4, 5] that combines the catalysts synthesis and deposition directly on the PEM membrane in one-step, which results in fast and facile fabrication of large scale (up to 1000 cm2) MEAs [4, 5]. In addition, this technology allows precise control of the composition, morphology, and particle size distribution of wide range of nanoparticles supported and unsupported on carbon, and thus ensures fine tuning of the catalysts’ activity and durability. The RSDT fabricated MEAs have improved activity and durability performance with one order of magnitude lower catalyst loadings in their electrodes in comparison to the state‐of‐the‐art commercial MEAs for PEM water electrolyzers [6]. In this work we report the results from the in‐situ and ex‐situ synchrotron X-ray Absorption Spectroscopy (XAS) studies of the Ir/IrOx (anode) and Pt/C (cathode) catalysts, fabricated by the RSDT. The experiments were performed at beamline 7-BM at NSLS II at Brookhaven National Laboratory. The electronic and atomic structures of the Ir and Pt in the catalyst layers after their fabrication, during operation at different cell voltages, and after long term steady‐state operation were studied by XANES and XAFS, respectively. The results obtained, provide better understanding of the improved activity of the catalysts, as well as of the degradation mechanisms that govern the MEAs’ failure. References https://www.energy.gov/sites/prod/files/2017/05/f34/fcto_myrdd_fuel_cells.pdf https://www.energy.gov/sites/prod/files/2015/06/f23/fcto_myrdd_production.pdf Kim, S., Myles, Maric, R., et al. Electrochimica Acta, 177, 190-200 (2015).Yu, H., Baricci, A., Bisello, A., Bonville, L., Maric, R., et al. Electrochimica Acta, 247, 1155-1168 (2017).Roller, J., Maric, R., 24(8) December 2015 pp. 1529-1541 (2015).Mirshekari, G., Ouimet, R., Zeng, Z, Yu, H., Bliznakov, S., Bonville, L., Niedzwiecki, A., Errico, S., Capuano, C., Mani, P., Ayers, K., Maric, R. International Journal for Hydrogen Energy, 46(2), 2021, pp. 1526-1539 (2021).