Membrane Electrode Assemblies Fabricated By Reactive Spray Deposition Technology for Advanced Proton Exchange Membrane Water Electrolyzers: Study of the Degradation Mechanisms

Abstract

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:10.1149/2.1441704jesButtler, 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).