Advanced Fuel Cell Catalyst based on Graphene

International audienceCarbon blacks supported Pt, currently widely used as electrocatalysts in Polymer Electrolyte Membrane Fuel Cells (PEMFC) are thermochemically unstable in PEMFC operating conditions. This is especially true at the cathode side where, on top of relatively elevated temperature (80°C) and acidic conditions, both the potential and the relative humidity may be high. The resulting carbon oxidation is partially responsible for the PEMFC performance decrease observed over time. Hence, long term durability still needs to be improved in order to consider PEMFC as credible alternatives to conventional power sources for automotive, stationary or portable applications.Much effort have been directed to identify and synthesize alternative carbon materials as catalyst supports for PEMFCs. One strategy to decrease carbon support corrosion is to use carbon with high extent of graphitization, which is supposed to decrease defect sites on the carbon structure, where carbon oxidation starts [1], [2]. However high graphitic content of carbon can be a brake for particle nucleation and dispersion. Among the different forms of carbon, graphene, a monolayer of graphite, has attracted increasing attention because of its unique two-dimensional (2D) single sheet of sp2 carbon in a hexagonal arrangement. Graphene possesses unique properties, such as high charge-carrier mobility (up to 105 cm2 V-1 s-1), super conductivity, ambipolar electric field effect, high mechanical strength (130 GPa), quantum Hall effects at room temperature, and high surface area (2,600 m2 g-1). These properties make graphene ideal for a wide potential applications such as in nanoelectronics, electrode support for catalysts in electrochemical energy systems, chemical and biological sensors, composite materials and biotechnology.Although graphene exhibits an attractive range of properties as catalyst supports for fuel cells (FC), they suffer from a serious issue. Integration of such catalyst in catalyst layer (CL) is complex due to the high cohesive van der Walls attractions between graphene sheets, named also pi-stacking of graphene layers, leading to serious blocking of the active surface area. To overcome this phenomena, one solution consists to add spacers or additives in graphene sheets such as carbon black, carbon nanotube and urea have been reported to be intercalated into Pt/graphene or with several applications in FCs [3]. In this work, platinum catalysts were synthetized on Graphene support, nanocharacterised, processed in ink and incorporated in fuel cell. Several techniques of MEA fabrication were used: CCB (catalyst coated backing), CCM (catalyst coated membrane) or CCM by decal (transfert on inert substrate). We investigated these new active layers at the cathode side in term of electrocatalytic performance and compared the electrochemical properties of these hybrid materials with a commercial Pt/C catalyst using carbon blacks as carbon support. Moreover, the use of additive was also studied to enhance performance by aerate active layer and avoid pi-stacking of graphene layer.The goal of the project is to demonstrate that the use of GRM based carbon supports can be promising in effectively reducing the carbon corrosion and then increase lifetime of the cell. Accelerated stress test has been done in 25cm² fuel cell setup on both AST for carbon support and fuel cell Dynamic Load Cycle, FC-DLC cycles.The GrapheneCore3 European program funds this work.References[1] Lu, Y; Applied Catalysis B: Environmental 199 (2016) 292-314.[2] Yadav, R.; Industrial & Engineering Chemistry Research 57 (2018) 9333-9350.[3] Suter, T. A. M. et al. Nanomaterials 11, 2530 (2021)