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Title: Understanding the Thermal Stability of Palladium–Platinum Core–Shell Nanocrystals by In Situ Transmission Electron Microscopy and Density Functional Theory

Core–shell nanocrystals offer many advantages for heterogeneous catalysis, including precise control over both the surface structure and composition, as well as reduction in loading for rare and costly metals. Although many catalytic processes are operated at elevated temperatures, the adverse impacts of heating on the shape and structure of core–shell nanocrystals are yet to be understood. In this work, we used ex situ heating experiments to demonstrate that Pd@Pt 4L core–shell nanoscale cubes and octahedra are promising for catalytic applications at temperatures up to 400 °C. We also used in situ transmission electron microscopy to monitor the thermal stability of the core–shell nanocrystals in real time. Our results demonstrate a facet dependence for the thermal stability in terms of shape and composition. Specifically, the cubes enclosed by {100} facets readily deform shape at a temperature 300 °C lower than that of the octahedral counterparts enclosed by {111} facets. A reversed trend is observed for composition, as alloying between the Pd core and the Pt shell of an octahedron occurs at a temperature 200 °C lower than that for the cubic counterpart. Density functional theory calculations provide atomic-level explanations for the experimentally observed behaviors, demonstrating that the barriers for edge reconstructionmore » determine the relative ease of shape deformation for cubes compared to octahedra. Furthermore, the opposite trend for alloying of the core–shell structure can be attributed to a higher propensity for subsurface Pt vacancy formation in octahedra than in cubes.« less
Authors:
ORCiD logo [1] ;  [2] ; ORCiD logo [1] ;  [2] ;  [3] ; ORCiD logo [4] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Georgia Inst. of Technology, Atlanta, GA (United States)
  2. Univ. of Wisconsin-Madison, Madison, WI (United States)
  3. Georgia Inst. of Technology, Atlanta, GA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
FG02-05ER15731
Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 11; Journal Issue: 5; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Research Org:
Univ. of Wisconsin-Madison, Madison, WI (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Contributing Orgs:
Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences; Center for Nanoscale Materials at Argonne National Laboratory; the Environmental Molecular Sciences Laboratory; the National Energy Research Scientific Computing Center (NERSC); and the UW-Madison Center for High Throughput Computing (CHTC)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; core−shell nanocrystal; density functional theory; electron microscopy; in situ heating; thermal stability
OSTI Identifier:
1398267

Vara, Madeline, Roling, Luke T., Wang, Xue, Elnabawy, Ahmed O., Hood, Zachary D., Chi, Miaofang, Mavrikakis, Manos, and Xia, Younan. Understanding the Thermal Stability of Palladium–Platinum Core–Shell Nanocrystals by In Situ Transmission Electron Microscopy and Density Functional Theory. United States: N. p., Web. doi:10.1021/acsnano.6b08692.
Vara, Madeline, Roling, Luke T., Wang, Xue, Elnabawy, Ahmed O., Hood, Zachary D., Chi, Miaofang, Mavrikakis, Manos, & Xia, Younan. Understanding the Thermal Stability of Palladium–Platinum Core–Shell Nanocrystals by In Situ Transmission Electron Microscopy and Density Functional Theory. United States. doi:10.1021/acsnano.6b08692.
Vara, Madeline, Roling, Luke T., Wang, Xue, Elnabawy, Ahmed O., Hood, Zachary D., Chi, Miaofang, Mavrikakis, Manos, and Xia, Younan. 2017. "Understanding the Thermal Stability of Palladium–Platinum Core–Shell Nanocrystals by In Situ Transmission Electron Microscopy and Density Functional Theory". United States. doi:10.1021/acsnano.6b08692. https://www.osti.gov/servlets/purl/1398267.
@article{osti_1398267,
title = {Understanding the Thermal Stability of Palladium–Platinum Core–Shell Nanocrystals by In Situ Transmission Electron Microscopy and Density Functional Theory},
author = {Vara, Madeline and Roling, Luke T. and Wang, Xue and Elnabawy, Ahmed O. and Hood, Zachary D. and Chi, Miaofang and Mavrikakis, Manos and Xia, Younan},
abstractNote = {Core–shell nanocrystals offer many advantages for heterogeneous catalysis, including precise control over both the surface structure and composition, as well as reduction in loading for rare and costly metals. Although many catalytic processes are operated at elevated temperatures, the adverse impacts of heating on the shape and structure of core–shell nanocrystals are yet to be understood. In this work, we used ex situ heating experiments to demonstrate that Pd@Pt4L core–shell nanoscale cubes and octahedra are promising for catalytic applications at temperatures up to 400 °C. We also used in situ transmission electron microscopy to monitor the thermal stability of the core–shell nanocrystals in real time. Our results demonstrate a facet dependence for the thermal stability in terms of shape and composition. Specifically, the cubes enclosed by {100} facets readily deform shape at a temperature 300 °C lower than that of the octahedral counterparts enclosed by {111} facets. A reversed trend is observed for composition, as alloying between the Pd core and the Pt shell of an octahedron occurs at a temperature 200 °C lower than that for the cubic counterpart. Density functional theory calculations provide atomic-level explanations for the experimentally observed behaviors, demonstrating that the barriers for edge reconstruction determine the relative ease of shape deformation for cubes compared to octahedra. Furthermore, the opposite trend for alloying of the core–shell structure can be attributed to a higher propensity for subsurface Pt vacancy formation in octahedra than in cubes.},
doi = {10.1021/acsnano.6b08692},
journal = {ACS Nano},
number = 5,
volume = 11,
place = {United States},
year = {2017},
month = {5}
}