Durability Loss Mechanisms and Sources in Proton Exchange Membrane-Based Electrolysis

Abstract

In commercial electrolysis today, the cost of electricity input drives the cost of hydrogen production. As electrochemical water splitting is coupled directly with low-cost power sources, however, capital cost at lower capacity (renewable input) will be a significant factor in hydrogen cost [1,2]. While a variety of components affect electrolysis capital cost, reducing catalyst loading (several milligrams per square centimeter today) will be necessary to approach hydrogen production cost targets. Efforts have begun to address electrolyzer durability at low catalyst loading and variable load/input profiles, to: establish single-cell durability baselines for catalyst development projects; evaluate how the type and magnitude of stressor influences single-cell performance over time; and assess the ability of potential control to limit in-situ durability losses [3]. Although commercial electrolyzers are durable today, thick catalyst layers appear to mask catalyst corrosion and delay loss observations. Moreover, intermittent operation associated with renewable load profiles significantly accelerate loss compared to constant load. Performance loss has been tied to decreasing kinetics, where both catalyst layer thinning and changes to the electrode structure were observed. Cell diagnostics has been used to evaluate resistances in the catalyst layer, and changes at the catalyst layer interface may contribute to the observed loss. A variety of factors were examined as the sources of catalyst loss, including the expected dissolution rate of test profiles, the frequency of load cycling, and the ramp rate to peak load [4,5]. Testing has expanded to expected operation profiles (wind, solar) to correlate accelerated stress tests to anticipated use and device lifetime. Recently, studies have expanded into other catalyst loss mechanisms, including start-stop operation and hydrogen crossover. Lower potentials in the anode catalyst layer reduce the catalyst surface and lead to particle agglomeration and increased dissolution rates. These factors have been included to assess various stressors resulting in catalyst loss and shorter device lifetime. [1] H2 at Scale: Deeply Decarbonizing our Energy System. Presented at Annual Merit Review, U.S. Department of Energy; Washington, DC, June 6−10, 2016. https://www.hydrogen.energy.gov/pdfs/review16/2016_amr_h2_at_scale.pdf.[2] Denholm, P.; O’Connell, M.; Brinkman, G.; Jorgenson, J. Overgeneration from Solar Energy in California: A Field Guide to the Duck Chart; Vol. NREL/TP-6A20-65023; National Renewable Energy Laboratory: Golden, CO, 2015. Available at the following: http://www.nrel.gov/docs/fy16osti/65023.pdf.[3] S. M. Alia, H2@Scale: Experimental Characterization of Durability of Advanced ElectrolyzerConcepts in Dynamic Loading, 2018. https://www.hydrogen.energy.gov/pdfs/review18/tv146_alia_2018_p.pdf. [4] Cherevko, S.; Geiger, S.; Kasian, O.; Kulyk, N.; Grote, J. P.; Savan, A.; Shrestha, B. R.; Merzlikin, S.; Breitbach, B.; Ludwig, A.; Mayrhofer, K. J. J. Cat. Today 2016, 262, 170.[5] S. M. Alia and G. C. Anderson, J. Electrochem. Soc., 2019, 166, F282-F294.