Scaling-up and Characterization of Ultra Low-loading MEAs by Electrospray Manufacturing

Kurzfassung

The electrospraying of liquid suspensions containing catalytic nanoparticles is being successfully used in the production of nano-structured porous catalytic layers for proton exchange membrane fuel cell (PEMFC) electrodes [1–3]. The aim of these works is to reduce the platinum loading by increasing the platinum utilization without compromising the fuel cell performance. Several methods, especially those based on sputtering [4], have been used to reduce the platinum loading on the electrodes. But these methods require a strict atmosphere control and vacuum conditions that make them relatively expensive and not easily adaptable to mass production. The benefits of electrospraying are the simplicity of the experimental set up (only a pump-needle system and a high voltage power supply), the high platinum utilization due to the small electrosprayed particle size and the easy scale-up suitable for industrial production [5–6]. Experimental Catalyst inks were prepared by dispersing Pt/C nanopowders (Pt 10 wt.% on Vulcan XC-72R) in ethanol mixed with Nafion. Electrodes with 0.01 mgPtcm-2 Pt loading were prepared by electrospraying the catalyst ink. The substrate consisted of a 25 cm2 square size TorayTM carbon paper coated with a carbon MPL. Nafion 212 and Nafion 211 were used as membranes, sandwiched between two equal electrodes to make a MEA without the need of hot-pressing. Results and Discussion Performances of 25 cm2 MEAs with N212 and previous results conducted with a 5 cm2 MEA are compared with 0.02 mgPtcm-2 Pt loading. In both cases, the operation conditions were the same, absolute pressure: 4.4 bars, temperature: 70 ºC, feeding gases: dry H2/O2. Both MEAs show very similar performances without any sign of penalty due to the scaling-up. The maximum performance reaches up to near 600 mW/cm2 that accounting for the overall 0.02 mgPt cm-2 (cathode plus anode) loading leads to a platinum utilization of 30 kW/gPt as reported above. These results are discussed with respect to their implications for the important road to lowering noble metal loading of PEFC in different applications