期刊
CHEMCATCHEM
卷 7, 期 22, 页码 3655-3664出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/cctc.201500380
关键词
alloy nanoparticles; in situ electron microscopy; iron; phase transition; platinum
资金
- NSERC
- APC (CaRPE-FC)
- NRC
Coupling electron microscopy techniques with insitu heating ability allows us to study phase transformations on the single-nanoparticle level. We exploit this setup to study disorder-to-order transformation of Pt-Fe alloy nanoparticles, a material that is of great interest to fuel-cell electrocatalysis and ultrahigh density information storage. In contrast to earlier reports, we show that Fe (instead of Pt) segregates towards the particle surface during annealing and forms a Fe-rich FeOx outer shell over the alloy core. By combining both exsitu and insitu approaches to probe the interplay between ordering and surface-segregation phenomena, we illustrate that the surface segregation of Fe precedes the ordering process and affects the ordered phase evolution dramatically. We show that the ordering initiates preferably at the pre-existent Fe-rich shell than the particle core. While the material-specific findings from this study open interesting perspectives towards a controlled phase evolution of Pt-Fe nanoalloys, the characterization methodologies described are general and should prove useful to probing a wide-range of nanomaterials.
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