Octahedral to Cuboctahedral Shape Transition in 6 nm Pt3Ni Nanocrystals for Oxygen Reduction Reaction Electrocatalysis |
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Authors: | Melina Zysler David Zitoun |
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Affiliation: | Department of Chemistry and Bar-Ilan Institute for Technology and Advanced Materials (BINA), Bar-Ilan University, Ramat Gan, 5290002 Israel |
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Abstract: | Pt3Ni stands as one of the most active electrocatalysts for the oxygen reduction reaction (ORR). The activity varies with the morphology of the nanocrystals with a high activity observed for the octahedral shape where only the high density {111} crystallographic planes are exposed. Herein, the synthesis of 6 nm Pt3Ni octahedral nanocrystals with a Pt enriched shell or cuboctahedral nanocrystals with a Ni enriched shell is described. Interestingly, the cuboctahedral nanocrystals display a six-pointed star/skeleton of platinum, which features a very uncommon atomic distribution. In the synthesis, a decrease in the oxygen partial pressure induces the transition from octahedral to cuboctahedral morphology. The octahedral and cuboctahedral nanocrystals both demonstrate high ORR activity (1.1 mA cm−2Pt and 1.2 A mg−1Pt at 0.9 V vs reversible hydrogen electrode (RHE) are the highest values obtained for PtNi-20 and PtNi-15, respectively). After exposure to oxidative conditions in the acidic electrolyte, the cuboctahedral nanoparticles with a pristine Ni-rich skin show a Pt skin and retain their cuboctahedral morphology. |
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Keywords: | cuboctahedral nanoparticles electrocatalysts oxygen reduction reaction Pt3Ni nanocrystals shape transitions |
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