Proton exchange membrane water electrolyzers (PEMWEs) have demonstrated enormous potential as the next generation hydrogen production technology. The main challenges that the state-of-the-art PEMWEs are currently facing are excessive cost and poor durability. Understanding the failure modes in PEMWEs is a key factor for improving their durability, lowering the precious metal loading, and hence cost reduction. In this work, reactive spray deposition technology (RSDT) has been used to fabricate a membrane electrode assembly (MEA) with one order of magnitude lower Pt and Ir catalyst loadings (0.2-0.3 mgPGM cm-2) in comparison to the precious metal loadings in the stat-of-the-art commercial MEAs (2–3 mgPGM cm-2). As fabricated MEA with an active area of 86 cm2, has been tested for over 5000 hours at steady-state conditions that are typical for an industrial hydrogen production system. Herein, we present and discuss the results from a comprehensive post-test analysis of the MEA of interest. The main degradation mechanisms, governing the performance loss in the RSDT fabricated MEA with ultra-low precious metal loadings, have been identified and discussed in detail. All failure modes are critically compared and the main degradation mechanism with the highest impact on the MEA performance loss among the others is identified.

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Despite the recent progress in increasing the power generation of Anion‐exchange membrane fuel cells (AEMFCs), their durability is still far lower than that of Proton exchange membrane fuel cells (PEMFCs). Using the complementary techniques of X‐ray micro‐computed tomography (CT), Scanning Electron Microscopy (SEM) and Energy Dispersive X‐ray (EDX) spectroscopy, we have identified Pt ion migration as an important factor to explain the decay in performance of AEMFCs. In alkaline media Pt+2 ions are easily formed which then either undergo dissolution into the carbon support or migrate to the membrane. In contrast to PEMFCs, where hydrogen cross over reduces the ions forming a vertical “Pt line” within the membrane, the ions in the AEM are trapped by charged groups within the membrane, leading to disintegration of the membrane and failure. Diffusion of the metal components is still observed when the Pt/C of the cathode is substituted with a FeCo−N−C catalyst, but in this case the Fe and Co ions are not trapped within the membrane, but rather migrate into the anode, thereby increasing the stability of the membrane.

The reactive spray deposition technology (RSDT) that has been developed at UConn, is one of the most promising new methodologies for direct fabrication of large scale MEAs for proton exchange membrane water electrolyzers (PEMWEs) with ultra-low platinum group metals (PGM) loadings in their catalyst layers [1,2]. The RSDT is an open to air flame assisted method for fabrication of MEAs that combines the catalysts synthesis and direct deposition on the Nafion® membrane in one step [2,3]. Thus, this method eliminates multiple time consuming and expensive steps in the MEA manufacturing process and reduces the fabrication time from days and weeks to hours. As a dry spray methodology with integrated system for in-situ quality control of the catalysts and catalyst layers (CLs),[1] the RSDT allows precise control of the catalysts composition, loading, porosity, thickness, and ionomer content. Furthermore, it has been demonstrated that by controlling the precursor solutions flow rates, and the flame deposition parameters, catalyst layers with gradient distribution in the nanoparticle size, as well as in the PGM loading in the CLs can be achieved, which ensures fine tuning of the activity and durability performance of the MEAs of interest [4].Herein, we will demonstrate the capabilities of the RSDT methodology to fabricate large scale MEAs for PEMWEs, that have one order of magnitude lower PGM loadings in the CLs and activity and durability performance comparable to the state-of-the-art commercial MEAs. RSDT fabricated MEAs with geometric area of the electrodes of 86 cm2 and 680 cm2, and loadings of 0.2 mgPt/cm2 in the cathode and 0.3 mgIr/cm2 in the anode have been tested at conditions typical for industrial electrolyzers. The performed long term steady-state test for over 5000 hours, as well as the measured polarization curves and EIS spectra clearly show excellent activity and durability performance of these MEAs. In addition, the RSDT fabricated MEAs have integrated recombination layers that effectively reduce the hydrogen crossover to below 10 %LFL. Furthermore, comprehensive post-test analysis of the MEAs after 5000 hours of operation has been performed and the degradation mechanisms governing their performance loss were identified and will be discussed in detail.References Mirshekari, G., Ouimet, R., Zeng, Z, Yu, H., Bliznakov, S., Bonville, L., Niedzwiecki, A., Errico, S., Capuano, C., Mani, P., Ayers, K., Maric, R., 2021.“High-Performance and Cost-Effective Membrane Electrode Assemblies for Advanced Proton Exchange Membrane Electrolyzers: Long-Term Durability Assessment”, International Journal for Hydrogen Energy, 46(2), 2021, pp. 1526-1539.Roller, J., Maric, R., 2015. A Study on Reactive Spray Deposition Technology Processing Parameters in the Context of Pt Nanoparticle Formation, Journal of Thermal Spray Technology, 24(8) December 2015 pp. 1529-1541.Yu, H., Baricci, A., Casalegno, A., Guetaz, L., Bonville, L., Maric, R., 2017. Strategies to mitigate Pt dissolution in low Pt loading proton exchange membrane f...

Proton exchange membrane water electrolyzers (PEMWEs) have demonstrated great potential as the next generation hydrogen production technology1,2. The main challenges that the state-of-the-art PEMWEs are currently facing are: (i) high cost, (ii) low efficiency, and (iii) poor durability performance3. Understanding the failure modes of PEMWEs during the operation is a key factor for improving their durability performance, as well as for lowering the precious metal loading in the catalyst layers and hence for reducing their cost. However, the catalyst degradation mechanisms in PEMWEs during operation, especially for the Ir-based anode catalysts, have not been fully understood. In this work, reactive spray deposition technology (RSDT) has been used to fabricate membrane electrode assemblies (MEAs) with one order of magnitude lower Pt and Ir catalyst loadings in their cathode and anode catalyst layers, respectively, in comparison to the precious metals loading in the state-of-the-art commercial MEAs for PEMWEs 4–6. Two of as- fabricated MEAs with geometric area of 86 cm2, have been tested at steady-state conditions that are typical for commercial hydrogen production system. One of the cells was stopped and disassembled after 50 hours of operation, while the second one was disassembled after it failed after over 500 hours of operation. Herein we present a comprehensive comparative study of both MEAs, aimed at identifying and understanding the degradation mechanisms causing the MEAs failure. The pre- and post-test MEA characterizations are performed by scanning/transmission electron microscopy (S/TEM), scanning electron microscopy (SEM), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD) and X-ray computed tomography (X-CT). In addition, rotating disk electrode (RDE) technique has been utilized for assessment of the catalytic activities of the RSDT-fabricated anode Ir/IrOx catalysts before and after the failure. The main degradation mechanisms, governing the failure modes in the MEAs of interest, have been identified and discussed. References Carmo, M., Fritz, D. L., Mergel, J. & Stolten, D. A comprehensive review on PEM water electrolysis. Int. J. Hydrogen Energy 38, 4901–4934 (2013). Babic, U. et al. Critical Review — Identifying Critical Gaps for Polymer Electrolyte Water Electrolysis Development Review — Identifying Critical Gaps for Polymer Electrolyte Water. (2017). doi:10.1149/2.1441704jes Buttler, A. & Spliethoff, H. Current status of water electrolysis for energy storage, grid balancing and sector coupling via power-to-gas and power-to-liquids: A review. Renew. Sustain. Energy Rev. 82, 2440–2454 (2018). Roller, J. M. & Maric, R. A Study on Reactive Spray Deposition Technology Processing Parameters in the Context of Pt Nanoparticle Formation. J. Therm. Spray Technol. 24, 1529–1541 (2015). Roller, J. M., Kim, S., Kwak, T., Yu, H. & Maric, R. A study on the effect of selected process parameters in a jet diffusion flame for Pt nanoparticle formation. J. Mater. Sci. 52, 9391–9409 (2017). Yu, H. et al. Nano-size IrOx catalyst of high activity and stability in PEM water electrolyzer with ultra-low iridium loading. Appl. Catal. B Environ. 239, 133–146 (2018).

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).