A noble metal-free catalyst based on N-doped carbon nanofibers supported on graphite (N-CNF 1 ) was employed for the oxygen reduction at the cathode of a Nafion PEMFC with a commercial Pt/C anode. Obtained performance in pure H2 and O2 indicated the presence of significant mass-transport limitations when utilizing catalyst loadings between 1 and 10 mg cm -2 . Strategies to reduce the limitations were explored by optimization of the cathode ionomer content, catalyst loading and application technique. Pore-formers (Li2CO3, (NH4)2CO3 and polystyrene microspheres) were utilized to improve the mass-transport within the layer. A maximum of 72 mW cm -2 and 1400 A g -1 or 300 W g -1 at peak power was demonstrated. The catalyst was then applied to the cathode of a 10-cell fuel cell stack, and a 400-hour durability test was conducted. The average cell voltage decay amounted to 162 µV h -1 . Finally, a market application analysis was conducted by comparing the capital and operating costs of FC systems based on Pt/C and on N-CNF cathodes. While the cheap (3,32 € g -1 ) N-CNF catalyst reduces the single MEA cost by almost a third, the total cost of ownership of an N-CNF based PEMFC system is still higher due to lower cell performance.
Next generation telecommunication satellites will demand increasingly more power. Power levels up to 50 kW are foreseen for the next decades. Battery technology that can sustain up to 50 kW for eclipse lengths of up to 72 minutes will represent a major impact on the total mass of the satellite, even with new Li-ion battery technologies. Regenerative fuel cell systems (RFCS) were identified years ago as a possible alternative to rechargeable batteries. CMR Prototech has investigated this technology in a series of projects initiated by ESA focusing on both the essential fuel cell technology, demonstration of cycle performance of a RFCS, corresponding to 15 years in orbit, as well as the very important reactants storage systems. In the last two years the development has been focused towards optimising the key elements of the RFCS; the HTPEM fuel cell and the High Pressure PEM electrolyser. In these ESA activities the main target has been to optimise the design by reducing the mass and at the same time improve the performance, thus increasing the specific energy. This paper will present the latest development, including the main results, showing that significant steps have been taken to increase TRL on these key components.
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