The Effect of Atomic Arrangements on the Oxygen Reduction Reaction Performance of Carbon-supported CoPtAg Catalysts

In this study, carbon-supported CoPtAg nanoparticles with different atomic ratios have been reduced under CO atmosphere and applied as electrocatalysts for oxygen reduction reaction (ORR). These samples with low Pt loading have comparable ORR activity and stability to Pt/C. An appropriate amount of Ag addition like 5 at % can effectively promote the performance of CoPt owing to the modification of the oxophilicity. Then carbon-supported Co₉₀Pt₅Ag₅ nanoparticles with different atomic arrangements have been reduced by different agents. The coordination numbers of Pt-Co and Co-Co (CN_Pt-Co and CN_Co-Co) of catalysts are related to their ORR activity and stability, respectively. Co90 sample with Ag and Pt randomly distributing within the Co matrix has high CN_Co-Co, which does not have positive effect on the ORR performance. On the other hand, Co90-1 sample with Ag and Pt cores within the Co matrix has the highest CN_Pt-Co and ORR activity ascribed to the electronic modification effect. However, it losses 32% ORR activity after accelerated durability test of 1000 cycles due to high CN_Co-Co. Co90-2 with Pt in the inner core and Ag on the outer shell structure has moderate CN_Pt-Co, very low CN_Co-Co, and un-filled d-states, which not only modify the oxophilicity but also benefit the ORR stability with a decay rate of 21%. We have demonstrated the atomic arrangement-performance relationship of highly stable and low Pt catalysts.