Single cell testing of newly developed materials in HT-PEM fuel cells

Kurzfassung

High temperature-polymer exchange membrane fuel cells (HT-PEM FC) combine many advantages among the various fuel cell technologies for stationary applications in the low to medium kW range. The DoE has set a target of 60,000 operating hours for stationary systems [1]. In order to achieve this goal under increased requirements for longevity and cost efficiency, key components in HT-PEM systems have to be improved. This challenging task is approached within the project HT-PEM 2.0, funded by the German Federal Ministry for Economic Affairs and Energy, with the participation of the industry. One task within the project is to compare MEAs with various confidential modifications of the membrane developed by the industry partners in terms of their performance and durability in order to identify best candidates for future application in HT-PEM FC stacks. Results of these tests and initial findings are presented for the first time in this presentation. Each MEA undergoes a so-called screening test. This comprises a break-in phase and Begin-of-Test (BoT) electrochemical characterisation (IV-curves, impedance spectra, cyclic voltammetry) in a test bench. Based on these results and additional ex-situ analyses like the determination of the acid discharge, promising MEAs are chosen to be additionally tested on their durability. This includes 310 load cycles between 0.6 A cm² for 4 minutes and 1.0 A cm-2 for 16 minutes, with an IV-curve every 62 cycles. Additionally, the described electrochemical characterisation before and after the cycling and ex-situ analyses are executed. This procedure was developed as part of the QUALIFIX project [2]. Compared to the state of the art, investigated in the QUALIFIX project, the results presented here show a clear development on MEAs within the framework of the HT-PEM 2.0 project. The most marked improvement can be seen at a decreased degradation rate over the load cycling test of one MEA with a rate of -15 µV h-1 at a current density of 1.0 A cm-2 compared to -98 µV h-1 in the QUALIFIX project. This indicates improvement within the MEA due to a constant power density over long time periods. Another result of this MEA is the in average roughly 20 % lower ohmic resistance, determined from impedance measurements. Further results, details of the tests and other MEAs will be part of the presentation.