Catalyst Assessments and Device Incorporation in Low Temperature Electrolysis

Abstract

Although hydrogen has a significant role in transportation and agriculture, its use in energy consumption overall has been limited, particularly when produced through electrochemical water splitting. With decreasing electricity prices, electrolysis cost reductions can be achieved and allow for an opportunity for greater use.(1) While load following renewable power sources can reduce feedstock cost, further cost reductions rely on minimizing the capital cost by reducing the platinum group metal (PGM) content.(2) Efforts are needed to understand and mitigate electrolyzer degradation, particularly when accounting for lower PGM loadings and intermittent operation.Previous efforts have developed accelerated stress tests focused on catalyst layer and interfacial loss with standard material sets. (3) Expanded studies have incorporated advanced materials, including higher surface areas, different oxide compositions, supports, and multicomponents. Kinetic improvements were found to lessen load requirements and can mitigate catalyst loss. Cell performance loss during extended operation, however, tended to qualitatively correspond to ex-situ dissolution rates of less stable materials leading to accelerated catalyst layer thinning, migration into the membrane, and interfacial tearing, as determined in post-mortem electron microscopy analysis.While individual components dictate cell-level performance and durability, how components are integrated into membrane electrode assemblies was found to have an impact on catalyst layer properties and electrolyzer performance/durability. Catalyst layers were modified using an ultrasonic spray approach due to the number of variables that could be tuned. While changes to these variables affect several properties and loss mechanisms, trends were found with regards to how catalyst-ionomer integration and catalyst layer uniformity affected performance nonidealities and how losses grew during extended operation. These approaches are useful in diagnostics, to identify and mitigate lower performance and durability. Understanding catalyst layer formation and the relationship between catalyst layer properties and electrolyzer performance/durability is critical to establishing baselines and better informing catalyst development and fabrication efforts.[1] B. Pivovar, N. Rustagi and S. Satyapal, The Electrochemical Society Interface, 27, 47 (2018).[2] K. Ayers, N. Danilovic, R. Ouimet, M. Carmo, B. Pivovar and M. Bornstein, Annual Review of Chemical and Biomolecular Engineering, 10, 219 (2019).[3] S. M. Alia, S. Stariha and R. L. Borup, J. Electrochem. Soc., 166, F1164 (2019).