• Hacker, Viktor
• Sandu, Daniel
• Heidinger, Mathias
• Edjokola, Joel
• Mayer, Kurt
• Bodner, Merit

Abstract

Degradation in polymer electrolyte fuel cells (PEFC) can be divided into chemical and physical degradation. Chemical degradation is greatly contributing to membrane degradation, which is a major contributor to reduced performance and lower efficiency. Chemical degradation of the membrane can be measured during operation, by analysing the effluent water from the cell. The chemical degradation is promoted by radical formation, which can occur on both the anode and the cathode side [1–3]. Low pH values and low relative humidities also increase chemical degradation by accelerating hydrogen peroxide (H2O2) production [4] and OCV conditions [5,6]. Oxygen-derived free radicals (HO* and HOO*) are formed in situ from hydrogen peroxide. These free radicals can react with the Nafion® membrane, leading to the emission of fluorides with the fuel cell exhaust. Fluoride emission and chemical degradation can also be caused by impurities in reactant gases or other sources of chemical degradation of the membrane [7,8]. Radical formation is enabled by Fenton active metals, whose presence can enable a homolytic oxygen bond cleavage, leading to radical formation [4]. Chemical degradation of the membrane can be identified by tracking the amount of fluorides in fuel cell effluent water.<br/><br/>Standards and synthetic test samples were prepared from ultrapure water and standard solutions. The fluoride concentration was determined using a calibration curve and standard addition. Potential interferences were evaluated by preparing test solutions, introducing different ions to standard samples. Matrix effects were evaluated by varying sample conditions to ensure consistent results. All samples are mixed with Zr(IV)-SPADNS2 and transferred to a cuvette for measurements [9].<br/><br/>Effluent water samples, standard and test samples are analysed using a UV-vis spectrometer developed by AiDEXA GmbH. This is done by monitoring the intensity in a given frequency range. The Zr(IV)-SPADNS2<br/> will react with fluorine present in the samples, causing a quenching reaction that reduces intensity in the peak intensity as well as causing a shift to lower wavelengths. Results from measurements can then be correlated to electrochemical measurements to obtain information about the correlation between chemical membrane degradation and fluoride emission. With this correlation, external measurements could be used for lifetime estimation based on the fluoride concentration present in effluent fuel cell water.<br/><br/><br/><br/>ACKNOWLEDGEMENT<br/>This research is performed under the projects HyLife (K-Project HyTechonomy, FFG grant number 882510) and B.GASUS (FFG grant number 884368), which are supported by the Austrian Research Promotion Agency (FFG).<br/><br/>REFERENCES<br/>[1] P. Frühwirt, A. Kregar, J.T. Törring, T. Katrašnik, G. Gescheidt, Phys. Chem. Chem. Phys. 22 (2020) 5647–5666.<br/>[2] A. Kregar, G. Tavčar, A. Kravos, T. Katrašnik, Appl. Energy 263 (2020) 114547.<br/>[3] M. Bodner, A. Schenk, D. Salaberger, M. Rami, C. Hochenauer, V. Hacker, Fuel Cells 17 (2017) 18–26.<br/>[4] M. Bodner, J. Senn, V. Hacker, in: Fuel Cells Hydrog. From Fundam. to Appl. Res., Elsevier, 2018, pp. 139–154.<br/>[5] M. Bodner, C. Hochenauer, V. Hacker, J. Power Sources 295 (2015) 336–348.<br/>[6] M. Bodner, B. Cermenek, M. Rami, V. Hacker, Membr. 2015, Vol. 5, Pages 888-902 5 (2015) 888–902.<br/>[7] B. Shabani, M. Hafttananian, S. Khamani, A. Ramiar, A.A. Ranjbar, J. Power Sources 427 (2019) 21–48.<br/>[8] X. Cheng, Z. Shi, N. Glass, L. Zhang, J. Zhang, D. Song, Z.S. Liu, H. Wang, J. Shen, J. Power Sources 165 (2007) 739–756.<br/>[9] R.M. Patel, K.S. Patel, M.L. Naik, Int. J. Environ. Stud. 56 (1999) 745–756.

Topics

• impedance spectroscopy
• polymer
• Oxygen
• glass
• glass
• Hydrogen
• quenching
• pH value