Title

Long-Range Segregation Phenomena In Shape-Selected Bimetallic Nanoparticles: Chemical State Effects

Keywords

AFM; diffusion; nanoparticle; octahedral; PtNi; PtNi alloy; segregation; XPS

Abstract

A study of the morphological and chemical stability of shape-selected octahedral Pt0.5Ni0.5 nanoparticles (NPs) supported on highly oriented pyrolytic graphite (HOPG) is presented. Ex situ atomic force microscopy (AFM) and in situ X-ray photoelectron spectroscopy (XPS) measurements were used to monitor the mobility of Pt0.5Ni0.5 NPs and to study long-range atomic segregation and alloy formation phenomena under vacuum, H2, and O2 environments. The chemical state of the NPs was found to play a pivotal role in their surface composition after different thermal treatments. In particular, for these ex situ synthesized NPs, Ni segregation to the NP surface was observed in all environments as long as PtOx species were present. In the presence of oxygen, an enhanced Ni surface segregation was observed at all temperatures. In contrast, in hydrogen and vacuum, the Ni outward segregation occurs only at low temperature (<200-270 C), while PtOx species are still present. At higher temperatures, the reduction of the Pt oxide species results in Pt diffusion toward the NP surface and the formation of a Ni-Pt alloy. A consistent correlation between the NP surface composition and its electrocatalytic CO oxidation activity was established. © 2013 American Chemical Society.

Publication Date

10-22-2013

Publication Title

ACS Nano

Volume

7

Issue

10

Number of Pages

9195-9204

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1021/nn403793a

Socpus ID

84887000521 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/84887000521

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