(Invited) Innovative Membrane Electrode Assemblies for the Next Generation Proton Exchange Membrane Water Electrolyzers

Abstract

The Hydrogen Economy (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. The HE implementation relies on the development of zero-carbon emission technologies for Hydrogen (H2) production. “Green” hydrogen can be produced at large scale by integration of water electrolyzers (WEs) with renewable energy sources. Currently, the proton exchange membrane water electrolyzers (PEMWEs) are considered to be the most advanced WEs that can be integrated with solar panels and wind turbines to produce large quantities of green H2. The main challenges that the state-of-the-art membrane electrode assemblies (MEAs) for PEMWEs are currently facing are: (i) high cost because of the high platinum group metals (PGM) loadings in their catalysts layers (2-3 mgPGM/cm2 in each electrode), and time consuming and expensive multi-step fabrication processes associated with their manufacturing; (ii) limited durability caused by the instability of the catalysts and the other cell components, and (iii) safety concerns associated with the hydrogen gas crossover and the absence of technologies that can effectively keep it below the safety level of the lower flammability limit (LFL) [1, 2, 3].In this work, we demonstrate the capabilities of a unique methodology for fabrication of advanced catalysts, catalyst layers, and MEAs for PEMWEs, known as Reactive Spray Deposition Technology (RSDT). 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 for application in PEM fuel cells and water electrolyzers [5, 6]. This technology allows precise control of the composition, morphology, and particle size distribution of a wide range of nanoparticles, supported and unsupported on carbon, and ensures fine tuning of the catalysts’ activity and durability. MEAs with geometric areas of 86 cm2 and 680 cm2, both with one order of magnitude lower PGM loading in their catalyst layers in comparison to the state-of-the-art MEAs for PEM water electrolyzers [6,7], are fabricated by the RSDT and evaluated for up to 5000 hours at current density of 1.8 A cm-2, 50 oC, and 400 psi differential hydrogen pressure. Diagnostic tests that include polarization curves, electrochemical impedance spectroscopy, linear sweep voltammetry, and hydrogen crossover measurements are performed periodically in order to evaluate the cell performance change during the long-term durability test. After the test, the MEAs are disassembled and subjected to comprehensive post test analysis. A wide range of techniques, including high-resolution TEM, STEM, EDS, SEM, ICP, XCT, XPS, and digital optical microscopy, have been used to study the degradation mechanisms governing the performance loss in the MEAs during the long-term steady state operation. The results from these tests will be presented and discussed in detail in this talk.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.pdfKlose, P. Trinke, T. Böhm, B. Bensmann, S. Vierrath, R. Hanke-Rauschenbach, and S. Thiele, J. Electrochem. Soc., 165, F1271–F1277 (2018).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).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).Ayers, K. Current Opinion in Electrochemistry, 18, 9–15 (2019).