Using Distribution of Relaxation Times Analysis to Explore Overpotentials in Proton Exchange Membrane Water Electrolyzers Utilizing Sintered Metal and Fibrous Titanium Porous Transport Layers
Authors: Gado Alanna M. , Bliznakov Stoyan , Bonville Leonard J. , Maric Radenka 
Published: November 2022

Proton exchange membrane water electrolyzers (PEMWEs) show potential for the clean production of renewable and high-purity hydrogen. [1] The widespread implementation of PEMWE usage faces performance and economic hurdles. In order to improve cell performance and durability, thus reducing capital cost, identifying and understanding the origins of performance losses is crucial. Overpotentials fall into three categories: ohmic, kinetic, and mass transport, which relate to various resistances within the cell during operation. Traditionally, electrochemical equivalent circuits (EEC) have been used to analyze electrochemical impedance spectroscopy (EIS) for polarizing processes, but this tool requires extensive background knowledge of both electrochemical processes and circuits. The use of distribution of relaxation times (DRT) as an EIS analysis tool allows for the objective distinguishing of individual and distinct electrochemical processes within the cell that contribute to these overpotentials [2,3,4]. DRT as an EIS analysis tool allows for more comprehensive understanding and comparison of overpotential processes, especially between cells of varying configurations. Understanding overpotential origins will provide a pathway for mitigating performance restricting processes and developing better performing, more durable, and more cost-effective build configurations.

In this work, several configurations of a single cell 25 cm2 PEMWE were tested. Cell performance using titanium fiber porous transport layers (PTLs) is compared against the use of sintered titanium PTLs, in both unplated and plated configurations. Four PEMWE cells were built using Bekaert unplated and plated titanium fiber PTLs, and Mott 20 mil unplated and plated sintered titanium PTLs. Results show good cell performance. DRT analysis of diagnostic data allows for the objective identification, discussion, and comparison of overpotential contributions.

References

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[2] Dierickx, S., Weber, A., & Ivers-Tiffée, E. (2020). How the distribution of relaxation times enhances complex equivalent circuit models for fuel cells. Electrochimica Acta, 355, 136764. https://doi.org/10.1016/j.electacta.2020.136764

[3] Ivers-Tiffée, E., Weber, A. (2017). Evaluation of electrochemical impedance spectra by the distribution of Relaxation Times. Journal of the Ceramic Society of Japan, 125(4), 193–201. https://doi.org/10.2109/jcersj2.16267

[4] Gado, A., Ouimet, R. J., Bonville, L., Bliznakov, S., & Maric, R. (2021). Analysis of electrochemical impedance spectroscopy using distribution of relaxation times for proton exchange membrane fuel cells and electrolyzers. ECS Meeting Abstracts, MA2021-02(41), 1261–1261. https://doi.org/10.1149/ma2021-02411261mtgabs