title: Surface faceting and elemental diffusion behaviour at atomic scale for alloy nanoparticles during in situ annealing.
abstract: The catalytic performance of nanoparticles is primarily determined by the precise nature of the surface and near-surface atomic configurations, which can be tailored by post-synthesis annealing effectively and straightforwardly. Understanding the complete dynamic response of surface structure and chemistry to thermal treatments at the atomic scale is imperative for the rational design of catalyst nanoparticles. Here, by tracking the same individual Pt3Co nanoparticles during in situ annealing in a scanning transmission electron microscope, we directly discern five distinct stages of surface elemental rearrangements in Pt3Co nanoparticles at the atomic scale: initial random (alloy) elemental distribution; surface platinum-skin-layer formation; nucleation of structurally ordered domains; ordered framework development and, finally, initiation of amorphization. Furthermore, a comprehensive interplay among phase evolution, surface faceting and elemental inter-diffusion is revealed, and supported by atomistic simulations. This work may pave the way towards designing catalysts through post-synthesis annealing for optimized catalytic performance.
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, One Bethel Valley Road, Building 4515, Oak Ridge, Tennessee 37831-6064, USA.
authors.forename: Miaofang
authors.initials: M
authors.lastname: Chi
authors.affiliation: Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pennsylvania 15260, USA.
authors.forename: Yinkai
authors.identifier: http://orcid.org/0000-0002-0200-1491
authors.initials: Y
authors.lastname: Lei
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pennsylvania 15260, USA.
authors.forename: Guofeng
authors.initials: G
authors.lastname: Wang
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Dongguo
authors.initials: D
authors.lastname: Li
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, One Bethel Valley Road, Building 4515, Oak Ridge, Tennessee 37831-6064, USA.
authors.forename: Karren L
authors.initials: KL
authors.lastname: More
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Lupini
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Lawrence F
authors.initials: LF
authors.lastname: Allard
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Nenad M
authors.initials: NM
authors.lastname: Markovic
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Vojislav R
authors.initials: VR
authors.lastname: Stamenkovic