Development of Membrane Electrode Assemblies for PEFC based on Aromatic Membranes

Kurzfassung

The paper presents the development and electrochemical testing of membrane electrode assemblies prepared by the DLR dry-spraying coating method on JSR aromatic membranes. The JSR membranes are composed of (sulfonated) aromatic block copolymer. The aim of this work is to demonstrate operation at elevated temperature up to 95 °C at reduced humidification of the cells on the way to achieve a temperature flexible stack. High temperature cell performance and stability is beneficial for numerous applications – e.g. in aircraft or residential cogeneration - as the cooling requirements are reduced and the cells and stacks can be operated with reduced control complexity. JSR membrane has contributed to the extension of the PEFC's operating temperature range (from temperatures of below zero to nearly 100 °C (or hot-dry conditions)). Using electrodes prepared by dry spraying the high temperature behaviour can be ascertained and a performance of 1 A cm-2 at 600 mV can be achieved at 95 °C. Variation of catalyst loading as well as gas diffusion layers demonstrates the balance between the conflicting goals of performance, cost reduction and durability. An impedance spectroscopy analysis of the cells for different membranes shows a good correlation with the expected conductivity of the various aromatic membranes as derived from ex-situ measurements and indicates a stable membrane performance. Observed degradation is mainly attributed to the electrodes thereby demonstrating the need to further optimize and develop the electrodes specifically for aromatic membranes. Further steps in this development process will be discussed.