Determination of Membrane Degradation in Polymer Electrolyte Fuel Cells with in-Situ and Ex-Situ Measurements

Abstract

Fuel cells convert chemical energy directly into electrical energy with high efficiency and without pollutants. The decomposition products in the clean exhaust gas caused by the chemical degradation of the membrane of polymer electrolyte fuel cells (PEFCs) can be used to monitor the service life of the cell. For perfluorinated sulfonic acid (PFSA)-based membranes, chemical degradation is investigated via ex situ monitoring of the effluent water. The decomposition of the PFSA backbone, which is part of the polymer electrolyte membrane (PEM), can be detected by the degradation products such as fluoride or fluorinated compounds [1]. There are multiple methods for measuring fluoride in water. We have developed a new method for the simple and precise measurement of fluoride based on the optical change caused by the quenching of a zirconium complex. This method requires only 900 µL of the sample and 100 µL of the complex [2].We have extended the two fluoride measurement methods, namely fluoride sensitive electrode (FSE) and photometry (PM), to include ion chromatography (IC). This serves as an additional point of comparison with high accuracy and expands the measuring scope to include other ions like sulfate and their potential influence on photometric measurements.The electrochemical characterization of the materials has been improved by adapted electrochemical impedance spectroscopy (EIS) equivalent circuits, which include a more detailed analysis of the contribution of degradation processes. Linear sweep voltammetry (LSV) was used to measure the gas crossover through the membrane. Cyclic voltammetry provides information about the change in electrochemical surface area. Electrochemical characterizations and fluoride measurements are supplemented by ex situ imaging methods to determine membrane thinning.[1] M. A. Yandrasits, A. Komlev, K. Kalstabakken, M. J. Kurkowski, and M. J. Lindell, “Liquid Chromatography/Mass Spectrometry Analysis of Effluent Water from PFSA Membrane Fuel Cells Operated at OCV,” J. Electrochem. Soc., vol. 168, no. 2, p. 024517, Feb. 2021, doi: 10.1149/1945-7111/abe56a.[2] M. Heidinger, E. Kuhnert, K. Mayer, D. Sandu, V. Hacker, and M. Bodner, “Photometric Method to Determine Membrane Degradation in Polymer Electrolyte Fuel Cells,” Energies 2023, Vol. 16, Page 1957, vol. 16, no. 4, p. 1957, Feb. 2023, doi: 10.3390/EN16041957.