Patterned Nafion membrane for proton exchange membrane fuel cell with ultra-low Pt catalyst loading

International audience; To reduce the cost of proton exchange membrane fuel cell (PEMFC), one approach is to minimize the amount of platinum. The use of physical vapor deposition process for the synthesis of efficient catalysts and for the development of fuel cells based on thin catalytic layers [1] has already significantly reduced the amount of platinum catalyst [2]. However, when the platinum catalyst is directly deposited on the membrane by magnetron sputtering (without the use of catalytic inks), the power density (in Wcm-2) delivered by the fuel cell is currently limited. Such fuel cell based on CCM architecture (catalyst coated membrane) with a Pt loading of 20 μgPtcm-2 is able to deliver up to 25 kilowatts per gram of platinum, while the power density is 0.5 Wcm-2.To improve the power density delivered by CCM fuel cell, the GREMI laboratory and the CEA aim to increase the membrane surface by using pulsed laser micromachining before the physical vapor deposition of Pt catalyst. A femtoseconde laser is used to create craters, dumps and ripples on the surface of stainless steel molds. These are then pressed against a Nafion membrane to print the negative of these patterns on one of its face. By using such process, micrometer and sub-micron designs appear on the surface of the Nafion membrane. The patterned membranes are then covered by Pt catalytic nanoclusters and tested in H2/O2 PEMFC. Their electrical characteristics are compared to fuel cell based on un-patterned membrane. Patterned membranes lead to an increase of the delivered power density. The most efficient fuel cell delivers 0.73 mWcm-2 with a Pt loading of 25 μgPtcm-2 on the cathode side. This improvement appears to come from an increase of the catalytic activity and of the membrane conductivity.REFERENCES[1] Pascal Brault, Amaël Caillard, Stève Baranton, Mathieu Mougenot, St¦phane Cuynet, and Christophe Coutanceau, ChemSusChem 2013 6, 1168–1171 [2] M. Cavarroc, A. Ennadjaoui, M. Mougenot, P. Brault, R. Escalier, Y. Tessier, J. Durand, S. Roualdès, T. Sauvage, C. Coutanceau, Electrochemistry Communications 2009 11 859–861