Tracking the Early-life of PtNi/C Shape-Controlled Catalysts upon their Integration in PEMFC

The integration of promising bimetallic electrocatalytic active materials for oxygen reduction reaction (ORR) into practical and functional proton-exchange membrane fuel cell (PEMFC) electrodes remains largely impeded by the poor performances that these exhibit at high current loads. The early life of PtNi/C catalysts presenting either structurally faceted/ordered or defective/disordered surface morphology is compared to that of both spherical PtNi/C and Pt/C catalysts. Different single-cell operating conditions were studied. At low current density, in the kinetically limited region, a good agreement between liquid electrolyte and single-cell configuration is reported and the kinetic benefit of PtNi/C catalysts compared to Pt/C is (at least partially) maintained. However, PtNi/C catalysts show severe limitations in the O 2 mass transport limited region. Morphological and compositional changes were monitored at each stage showing that Ni atoms are leached at every step from ink formulation to the first PEMFC test. We show that Ni is already redistributed in the membrane in the fresh membrane electrode assembly (MEA) state. Ni 2+ cationic contamination of the ionomer/membrane contributes to the disappointing results obtained in MEA configuration. In addition, for shaped-controlled PtNi/C, the surface faceting loss combined with restructuring via coalescence and crystallite growth further compromise their transfer in technological devices.