title: Kirkendall effect and lattice contraction in nanocatalysts: a new strategy to enhance sustainable activity.
abstract: Core-shell nanoparticles increasingly are found to be effective in enhancing catalytic performance through the favorable influence of the core materials on the active components at the surface. Yet, sustaining high activities under operating conditions often has proven challenging. Here we explain how differences in the components' diffusivity affect the formation and stability of the core-shell and hollow nanostructures, which we ascribe to the Kirkendall effect. Using Ni nanoparticles as the templates, we fabricated compact and smooth Pt hollow nanocrystals that exhibit a sustained enhancement in Pt mass activity for oxygen reduction in acid fuel cells. This is achieved by the hollow-induced lattice contraction, high surface area per mass, and oxidation-resistant surface morphology--a new route for enhancing both the catalysts' activity and durability. The results indicate challenges and opportunities brought by the nanoscale Kirkendall effect for designing, at the atomic level, nanostructures with a wide range of novel properties.
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, United States. jia@bnl.gov
authors.forename: Jia X
authors.initials: JX
authors.lastname: Wang
authors.forename: Chao
authors.initials: C
authors.lastname: Ma
authors.forename: YongMan
authors.initials: Y
authors.lastname: Choi
authors.forename: Dong
authors.initials: D
authors.lastname: Su
authors.forename: Yimei
authors.initials: Y
authors.lastname: Zhu
authors.forename: Ping
authors.initials: P
authors.lastname: Liu
authors.forename: Rui
authors.initials: R
authors.lastname: Si
authors.forename: Miomir B
authors.initials: MB
authors.lastname: Vukmirovic
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Radoslav R
authors.initials: RR
authors.lastname: Adzic