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Title: Structure and stability of CaH 2 surfaces: on the possibility of electron-rich surfaces in metal hydrides for catalysis

Abstract

Structure, thermodynamic stability, and electronic properties of CaH 2 surfaces in (001),(110), and (111) crystallographic orientations are investigated using ab initio modeling. We show that stoichiometric surfaces terminated with a hydrogen atomic plane are the most energetically favorable and discuss properties of hydrogen vacancies (VH) at these surfaces. The average calculated work function of the most stable pristine surfaces (~5.2 eV) is in agree-ment with experimental data for powder samples. Neutral hydrogen vacancies host localized electrons and induce defect states in the band gap, thereby shifting the effective work function to much lower values of ~2.7 eV. Surface VH are predicted to aggregate into dimers and form electron-rich centers (e -)Ca 2+(e -) stable to over 800 K. These results suggest that hydrogen-deficient surfaces of CaH 2 can host a large concentration of localized electrons and, thus, give rise to new catalytic functionalities involving electron transfer between the surface, catalysts supported on it, and reacting species.

Authors:
ORCiD logo; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1372984
Report Number(s):
PNNL-SA-121592
Journal ID: ISSN 2050-7488; JMCAET
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Materials Chemistry. A
Additional Journal Information:
Journal Volume: 5; Journal Issue: 11; Journal ID: ISSN 2050-7488
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Ong, Phuong-Vu, Johnson, Lewis E., Hosono, Hideo, and Sushko, Peter V. Structure and stability of CaH 2 surfaces: on the possibility of electron-rich surfaces in metal hydrides for catalysis. United States: N. p., 2017. Web. doi:10.1039/C6TA09561E.
Ong, Phuong-Vu, Johnson, Lewis E., Hosono, Hideo, & Sushko, Peter V. Structure and stability of CaH 2 surfaces: on the possibility of electron-rich surfaces in metal hydrides for catalysis. United States. doi:10.1039/C6TA09561E.
Ong, Phuong-Vu, Johnson, Lewis E., Hosono, Hideo, and Sushko, Peter V. Sun . "Structure and stability of CaH 2 surfaces: on the possibility of electron-rich surfaces in metal hydrides for catalysis". United States. doi:10.1039/C6TA09561E.
@article{osti_1372984,
title = {Structure and stability of CaH 2 surfaces: on the possibility of electron-rich surfaces in metal hydrides for catalysis},
author = {Ong, Phuong-Vu and Johnson, Lewis E. and Hosono, Hideo and Sushko, Peter V.},
abstractNote = {Structure, thermodynamic stability, and electronic properties of CaH2 surfaces in (001),(110), and (111) crystallographic orientations are investigated using ab initio modeling. We show that stoichiometric surfaces terminated with a hydrogen atomic plane are the most energetically favorable and discuss properties of hydrogen vacancies (VH) at these surfaces. The average calculated work function of the most stable pristine surfaces (~5.2 eV) is in agree-ment with experimental data for powder samples. Neutral hydrogen vacancies host localized electrons and induce defect states in the band gap, thereby shifting the effective work function to much lower values of ~2.7 eV. Surface VH are predicted to aggregate into dimers and form electron-rich centers (e-)Ca2+(e-) stable to over 800 K. These results suggest that hydrogen-deficient surfaces of CaH2 can host a large concentration of localized electrons and, thus, give rise to new catalytic functionalities involving electron transfer between the surface, catalysts supported on it, and reacting species.},
doi = {10.1039/C6TA09561E},
journal = {Journal of Materials Chemistry. A},
issn = {2050-7488},
number = 11,
volume = 5,
place = {United States},
year = {2017},
month = {1}
}

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