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Title: Improving the Thermodynamic Stability of Aluminate Spinel Nanoparticles with Rare Earths

Abstract

Surface energy is a key parameter to understand and predict the stability of catalysts. In this work, the surface energy of MgAl 2O 4, an important base material for catalyst support, was reduced by using dopants prone to form surface excess (surface segregation): Y 3+, Gd 3+, and La 3+. The energy reduction was predicted by atomistic simulations of spinel surfaces and experimentally demonstrated by using microcalorimetry. The surface energy of undoped MgAl 2O 4 was directly measured as 1.65 ± 0.04 J/m 2 and was reduced by adding 2 mol % of the dopants to 1.55 ± 0.04 J/m 2 for Y-doping, 1.45 ± 0.05 J/m 2 for Gd-doping, and 1.26 ± 0.06 J/m 2 for La-doping. Atomistic simulations are qualitatively consistent with the experiments, reinforcing the link between the role of dopants in stabilizing the surface and the energy of segregation. Surface segregation was experimentally assessed using electron energy loss spectroscopy mapping in a scanning transmission electron microscopy image. Finally, the reduced energy resulted in coarsening inhibition for the doped samples and, hence, systematically smaller particle sizes (larger surface areas), meaning increased stability for catalytic applications. Moreover, both experiment and modeling reveal preferential dopant segregation to specific surfaces,more » which leads to the preponderance of {111} surface planes and suggests a strategy to enhance the area of desired surfaces in nanoparticles for better catalyst support activity.« less

Authors:
 [1];  [1];  [1];  [2];  [3]; ORCiD logo [3];  [1]
  1. Univ. of California, Davis, CA (United States). Dept. of Materials Science and Engineering, and Nanomaterials in the Environment, Agriculture, and Technology- Organized Research Unit (NEAT ORU)
  2. Arizona State Univ., Tempe, AZ (United States). John Cowley Center for High Resolution Electron Microscopy, LeRoy Eyring Center for Solid State Science (HREM, LE-CSSS)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC). Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1369180
Report Number(s):
LA-UR-16-22939
Journal ID: ISSN 0897-4756 ; 1520-5002 (Electronic)
Grant/Contract Number:  
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 28; Journal Issue: 14; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Hasan, M. M., Dey, Sanchita, Nafsin, Nazia, Mardinly, John, Dholabhai, Pratik, Uberuaga, Blas P., and Castro, Ricardo H. R. Improving the Thermodynamic Stability of Aluminate Spinel Nanoparticles with Rare Earths. United States: N. p., 2016. Web. doi:10.1021/acs.chemmater.6b02577.
Hasan, M. M., Dey, Sanchita, Nafsin, Nazia, Mardinly, John, Dholabhai, Pratik, Uberuaga, Blas P., & Castro, Ricardo H. R. Improving the Thermodynamic Stability of Aluminate Spinel Nanoparticles with Rare Earths. United States. doi:10.1021/acs.chemmater.6b02577.
Hasan, M. M., Dey, Sanchita, Nafsin, Nazia, Mardinly, John, Dholabhai, Pratik, Uberuaga, Blas P., and Castro, Ricardo H. R. Wed . "Improving the Thermodynamic Stability of Aluminate Spinel Nanoparticles with Rare Earths". United States. doi:10.1021/acs.chemmater.6b02577. https://www.osti.gov/servlets/purl/1369180.
@article{osti_1369180,
title = {Improving the Thermodynamic Stability of Aluminate Spinel Nanoparticles with Rare Earths},
author = {Hasan, M. M. and Dey, Sanchita and Nafsin, Nazia and Mardinly, John and Dholabhai, Pratik and Uberuaga, Blas P. and Castro, Ricardo H. R.},
abstractNote = {Surface energy is a key parameter to understand and predict the stability of catalysts. In this work, the surface energy of MgAl2O4, an important base material for catalyst support, was reduced by using dopants prone to form surface excess (surface segregation): Y3+, Gd3+, and La3+. The energy reduction was predicted by atomistic simulations of spinel surfaces and experimentally demonstrated by using microcalorimetry. The surface energy of undoped MgAl2O4 was directly measured as 1.65 ± 0.04 J/m2 and was reduced by adding 2 mol % of the dopants to 1.55 ± 0.04 J/m2 for Y-doping, 1.45 ± 0.05 J/m2 for Gd-doping, and 1.26 ± 0.06 J/m2 for La-doping. Atomistic simulations are qualitatively consistent with the experiments, reinforcing the link between the role of dopants in stabilizing the surface and the energy of segregation. Surface segregation was experimentally assessed using electron energy loss spectroscopy mapping in a scanning transmission electron microscopy image. Finally, the reduced energy resulted in coarsening inhibition for the doped samples and, hence, systematically smaller particle sizes (larger surface areas), meaning increased stability for catalytic applications. Moreover, both experiment and modeling reveal preferential dopant segregation to specific surfaces, which leads to the preponderance of {111} surface planes and suggests a strategy to enhance the area of desired surfaces in nanoparticles for better catalyst support activity.},
doi = {10.1021/acs.chemmater.6b02577},
journal = {Chemistry of Materials},
number = 14,
volume = 28,
place = {United States},
year = {Wed Jun 29 00:00:00 EDT 2016},
month = {Wed Jun 29 00:00:00 EDT 2016}
}

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