The development of Pt-based alloys
for oxygen reduction reaction
(ORR) is an important subject to enhance the performance of polymer
electrolyte membrane fuel cells (PEMFCs) and metal–air batteries.
Herein, ORR on Pt alloys with smaller and larger dopants in both Pt-shelled
and cored alloys have been extensively investigated from both computational
and experimental approaches to rationalize the detailed mechanism.
Our density functional theory (DFT) based calculations found that
Pt alloying with smaller dopants (Co, Cu, Pd) is thermodynamically
stable at Pt-shelled structures and their improved ORR activity originates
from ligand and geometric effects. On the other hand, Pt alloying
with larger and less reactive dopants, such as Au, thermodynamically
favors Pt-cored structure and shows the best ORR activity through
ensemble effect of surface dopant. Additionally, our results revealed
that d-band center of surface Pt can be correlated to ORR activity
for Pt-shelled alloys, but not to Pt-cored ones. The computational
predictions were in consistent with specific and mass activity measurements
in the electrochemical experiment. Our computational and experimental
efforts provided the conceptual foundation for the understanding of
ORR mechanism on Pt alloys in both shelled and cored forms and for
the first time concluded that Pt alloying with Au will show the best
ORR activity through the ensemble effect from the chemistry viewpoint.
The combinational modification of the morphology, alloying, and support for Pt catalysts has been optimized towards the oxygen reduction reaction. Graphene-supported PtPd nanorods have lower unfilled Pt d-states than carbon-supported Pt nanoparticles (Pt/C) and their specific and mass activities after the accelerated durability test are about 6.5 and 2.7 times higher than those of Pt/C, attributed to the synergistic electronic modification effect and graphene-metal interaction.
The one-dimensional structure and the electronic modification effect result in the excellent ORR activity and durability of Pt3Pd nanorods synergistically.
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