title: Evidence and Model for Strain-Driven Release of Metal Nanocatalysts from Perovskites during Exsolution.
abstract: The evolution of the surface morphology during exsolution of Ni from the perovskite La0.4Sr0.4Ti0.97Ni0.03O3-δ under reducing conditions was determined using atomic force microscopy. The exsolution process was found to initially induce the formation of a 20-30 nm deep pit on the oxide surface followed by the emergence of a Ni particle at the bottom of the pit. Continued emergence of the particle results in it nearly filling the pit, producing a unique structure in which the Ni particle is socketed into the oxide surface. We also show that this morphological evolution can be explained using a simple energy-based model that accounts for the interplay between the surface free energy and the strain energy induced by the included metal nucleate. The unique socketed structure results in strong anchorage between the exsolved particles and the oxide host lattice, which imparts both high thermal stability and unique catalytic activity.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Pennsylvania , 311A Towne Building, 220 South 33rd Street, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Tae-Sik
authors.initials: TS
authors.lastname: Oh
authors.affiliation: Department of Materials Science and Engineering, University of Pennsylvania , 3231 Walnut Street, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Ehsan K
authors.initials: EK
authors.lastname: Rahani
authors.affiliation: School of Chemistry, University of St. Andrews , Fife KY16 9ST, Scotland, United Kingdom.
authors.forename: Dragos
authors.initials: D
authors.lastname: Neagu
authors.affiliation: School of Chemistry, University of St. Andrews , Fife KY16 9ST, Scotland, United Kingdom.
authors.forename: John T S
authors.initials: JT
authors.lastname: Irvine
authors.affiliation: Department of Materials Science and Engineering, University of Pennsylvania , 3231 Walnut Street, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Vivek B
authors.initials: VB
authors.lastname: Shenoy
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Pennsylvania , 311A Towne Building, 220 South 33rd Street, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Gorte
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Pennsylvania , 311A Towne Building, 220 South 33rd Street, Philadelphia, Pennsylvania 19104, United States.
authors.forename: John M
authors.initials: JM
authors.lastname: Vohs
keywords: atomic force microscopy; metal exsolution; perovskite; strain