In:
ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2016-02, No. 38 ( 2016-09-01), p. 2353-2353
Abstract:
In recent years phosphoric acid doped PBI-type fuel cells have drawn much attention as a promising candidate for energy storage and conversion applications at relatively high temperatures (100 – 200 °C). The elevated operating temperature of HT-PEMFCs (high-temperature polymer electrolyte membrane fuel cells) simplifies water and thermal management. In addition, it greatly enhances the fuel cell’s tolerance against impurities (e.g. CO) in hydrogen, which is critical for operation with reformate hydrogen. However, durability and stability of high-temperature PEM-MEAs still need to improve for widespread commercialization [1], and better tools for identifying performance-loss related mechanisms are desirable. A very useful in-situ technique for performance analysis of HT-PEMFCs is electrochemical impedance spectroscopy (EIS). As previously reported, EIS can be used to characterize the impact of different parameters (e.g. stoichiometry, temperature, etc.) on cell kinetics [2, 3] . Equivalent circuit models are usually used to analyze the EIS data and identify the performance-loss related mechanisms. A major drawback of this approach is that the assumptions for the model equivalent circuits are sometimes ambiguous or even misleading due to the lack of priori knowledge about the electrochemical system under study. Furthermore, a clear separation of various physiochemical processes is difficult if the time constants of these processes overlap significantly in the frequency domain. To overcome these drawbacks, advanced mathematical methods such as Distribution of Relaxation Times (DRT) can be applied. DRT relies on the representation of the polarization impedance by its characteristic time constants and is numerically approximated by a discrete distribution function. This method has been successfully demonstrated for process identification and separation in solid oxide fuel cells (SOFC) [4]. In this study, we applied this technique on high temperature PEM-MEAs for the first time. Electrochemical processes were identified and analyzed by varying cell parameters such as temperature and stoichiometry. The results offer a refined understanding of loss mechanisms and provide valuable guidance for fuel cell improvement and optimization. [1] A. Chandan, M. Hattenberger, A. El-kharouf, S. Du, A. Dhir, V. Self, B.G. Pollet, A. Ingram, W. Bujalski, J. Power Sources 231 (2013) 264 [2] J. L. Jesperesen, E. Schaltz, S.K. Kær, J. of Power Sources 191 (2009) 289-296 [3] F. Mack, R. Laukenmann, S. Galbiati, J. A. Kerres, R. Zeis, ECS Transactions 69 (17), 1075-1087 (2015) [4] A. Leonide, V. Sonn, A. Weber, and E. Ivers-Tiffée, Journal of the Electrochemical Society 155 (1) B36-B41 (2008) Figure 1 Typical Nyquist plot of a phosphoric acid doped PBI-type HT-PEMFC at different current densities (a) and the corresponding distribution function (b). Figure 1
Type of Medium:
Online Resource
ISSN:
2151-2043
DOI:
10.1149/MA2016-02/38/2353
Language:
Unknown
Publisher:
The Electrochemical Society
Publication Date:
2016
detail.hit.zdb_id:
2438749-6
