Single Cell and Short Stack Evaluation of Cathode Backpressure Effects on Low Temperature Proton Exchange Membrane Water Electrolysis Anode Catalyst Performance and Degradation
Authors: Medina Samantha , Chan Ai-Lin , Duarte Ricardo P. M. , Ruple Matthew J , Alia Shaun M 
Published: December 2024

In order to enable the H2@Scale vision1 and to achieve low-cost hydrogen production that is competitive with steam methane reformation, it is necessary to decrease the capital cost and this can be done by leveraging variable renewable energy as an electricity feedstock for low temperature proton exchange membrane (PEM) electrolyzers.2 Despite this, cost and durability are still current challenges in state-of-the art water electrolysis systems. More research is needed to better understand the effects of dynamic operation on electrolyzer degradation. Understanding the degradation mechanisms governing intermittent electrolysis operation can enable future improvements related to component design and system operation. Furthermore, electrolyzers operating at differential pressures and producing electrochemically compressed hydrogen could decrease the hydrogen production cost by eliminating the need for equipment related to mechanical compression.3

To address polymer electrolyte membrane (PEM) electrolyzer durability concerns and develop effective degradation mitigation strategies, it is important to understand electrode and membrane degradation mechanisms at both the single cell and stack level. The focus of this research is to advance our current understanding of the anode catalyst layer (CL) degradation mechanisms observed for single cells and short stacks (4-10 cells) under relevant operating conditions (i.e. applying cathode backpressure).

Building upon recent investigations of continual intermittent operation at the single cell level4,5 this work continues to probe the intricacies of anode catalyst layer degradation. In this study, single cell hydrogen cross-over rates were varied by cathode backpressure conditions (ambient to 30 Bar) and were compared to elucidate the impact hydrogen has on anode catalyst layer degradation. Short stack polarization curves (ambient to 30 Bar), durability performance, and diagnostics measurements were compared to relevant single cell experiments, and differences in cell voltage losses, and CL resistance were observed. Durability test durations varied from 168 – 500+ hrs, and the electrolyzer operating temperatures were 80°C (single cell) and 75°C (short stack). Hydrogen cross-over rates were found to correlate to single cell potential during operational shutdowns. Electrochemical impedance spectroscopy further demonstrates higher degrees of kinetic loss and the immergence of additional loss mechanisms. The findings presented in this research contribute to the fundamental understanding of low-temperature PEM electrolysis dynamics under cathode backpressure conditions for single cells and short stacks. The implications of this research offer practical insights for the design and operation of efficient and durable electrolysis systems crucial for the advancement of sustainable hydrogen production technologies.

(1) H2@Scale. Hydrogen and Fuel Cell Technologies Office. https://www.energy.gov/eere/fuelcells/h2scale.

(2) Mark, R.; Jadun, P.; Gilroy, N.; Connelly, E.; Boardman, R.; Simon, A. J.; Elgowainy, A.; Zuboy, J. The Technical and Economic Potential of the H2@Scale Concept within the United States; NREL/TP-6A20-77610; National Renewable Energy Laboratory: Golden, CO, 2020.

(3) Ragnhild Hancke, Thomas Holm, and Øystein Ulleberg, “The Case for High-Pressure PEM Water Electrolysis,” Energy Conversion and Management 261 (2022): 115642, https://doi.org/10.1016/j.enconman.2022.115642.

(4) Alia, S. M.; Reeves, K. S.; Yu, H.; Park, J.; Kariuki, N.; Kropf, A. J.; Myers, D. J.; Cullen, D. A. Electrolyzer Performance Loss from Accelerated Stress Tests and Corresponding Changes to Catalyst Layers and Interfaces. Journal of The Electrochemical Society
2022, 169 (5), 054517. https://doi.org/10.1149/1945-7111/ac697e.

(5) A. Weiß et al., “Impact of Intermittent Operation on Lifetime and Performance of a PEM Water Electrolyzer,” Journal of The Electrochemical Society 166, no. 8 (April 29, 2019): F487, https://doi.org/10.1149/2.0421908jes.

Figure 1