High performance Fe and N-codoped graphene quantum dot supported Pd3Co catalyst with synergistically improved oxygen reduction activity and great methanol tolerance

Designing highperformance and durable nonplatinum catalysts as oxygen reduction reaction (ORR) catalysts is still a major barrier of fuel cell commercialization. In this work, simple hydrothermal and impregnation routes were applied to prepare nonplatinum PdCo bimetallic nanocatalysts such as FeN doped graphene quantum dot (FeNGQD) supported Pd3Co (Pd3Co/FeNGQD 10 wt%), carbon supported Pd3Co/C (10 wt%), graphene quantum dot supported Pd3Co/C (10 wt%). The synthesized catalysts were physicochemically characterized by Xray diffraction (XRD), Raman spectroscopy, transmission electronmicroscopy (TEM), and Xray photoelectron spectroscopy (XPS). The electrochemical investigation was carried out in three electrode halfcell system to evaluate the catalyst activity for oxygen reduction reaction (ORR), the tolerance to methanol crossover and durability. In comparison to commercial Pt/C (ETEK, 20 wt%), the Pd3Co/FeNGQD with lower weight percentage catalyst (similar to 10 wt%) displayed comparable electrocatalytic activity toward ORR with even higher methanol-tolerance capability and durability. The fabricated Pd3Co/FeNGQD with (10 wt %) metal loading exhibited only 20% lower activity than Pt/C (ETEK, 20 wt%) toward ORR. Nevertheless the durability study of the catalyst in acidic media showed that the Pd3Co/FeNGQD preserve 40% of its activity while Pt/C (ETEK, 20 wt %) exhibited only 20% of its initial catalytic activity for ORR. Moreover the activity loss in the presence of methanol (0.1 M) was obtained for Pt/C (ETEK, 20 wt%) and Pd3Co/FeNGQD 35% and 14%, respectively. To investigate the role of catalyst support, catalytic activities of Pd3Co/FeNGQD, Pd3Co/C, Pd3Co/GQD and Pd/FeNGQD were compared. The results demonstrated superior catalytic activity of Pd3Co/FeNGQD which could be related to the cocatalytic role of FeNGQD due to the presence numerous of active sites exposed to the reactants.