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Title: Optimizing proton conductivity in zirconates through defect engineering

Abstract

The alkaline-earth zirconates (CaZrO 3, SrZrO 3, and BaZrO 3) are under active investigation as solid-state electrolytes in hydrogen fuel cells. Their performance as proton conductors depends critically on the properties of acceptor dopants. Here, we use first-principles calculations to study the role of acceptors and point defects in incorporating protons through an oxygen-vacancy-mediated process. For CaZrO 3, we find that Zr Ca antisites suppress formation of oxygen vacancies. Other intrinsic point defects are shown not to hinder performance. Common unintentional impurities, such as C and N, are not good acceptors but can incorporate in other configurations. Our results show that the effectiveness of common dopants such as Sc and Y is limited by self-compensation due to their incorporation on the "wrong" cation site, where they act as donors. We demonstrate that using alkali metal dopants overcomes this problem, as the formation energy of compensating donors is very high. Alkali metal dopants also have low binding energies for protons, reducing their tendency to act as traps and hence enhancing proton conductivity. As a result, our guidelines for choosing acceptor dopants and optimizing synthesis conditions can greatly improve the efficacy of these proton-conducting oxides as solid-state electrolytes.

Authors:
ORCiD logo [1];  [2]; ORCiD logo [1]
  1. Univ. of California, Santa Barbara, CA (United States). Materials Dept.
  2. Univ. of California, Santa Barbara, CA (United States). Materials Dept.; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Energy Technologies Area
Publication Date:
Research Org.:
Univ. of California, Santa Barbara, CA (United States). Materials Dept.
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1499049
Grant/Contract Number:  
FG02-07ER46434
Resource Type:
Accepted Manuscript
Journal Name:
ACS Applied Energy Materials
Additional Journal Information:
Journal Name: ACS Applied Energy Materials; Journal ID: ISSN 2574-0962
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
13 HYDRO ENERGY; 36 MATERIALS SCIENCE; 08 HYDROGEN; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Proton conductors; zirconates; BaZrO3; hydrogen

Citation Formats

Rowberg, Andrew J. E., Weston, Leigh, and Van de Walle, Chris G.. Optimizing proton conductivity in zirconates through defect engineering. United States: N. p., 2019. Web. doi:10.1021/acsaem.8b02222.
Rowberg, Andrew J. E., Weston, Leigh, & Van de Walle, Chris G.. Optimizing proton conductivity in zirconates through defect engineering. United States. doi:10.1021/acsaem.8b02222.
Rowberg, Andrew J. E., Weston, Leigh, and Van de Walle, Chris G.. Tue . "Optimizing proton conductivity in zirconates through defect engineering". United States. doi:10.1021/acsaem.8b02222.
@article{osti_1499049,
title = {Optimizing proton conductivity in zirconates through defect engineering},
author = {Rowberg, Andrew J. E. and Weston, Leigh and Van de Walle, Chris G.},
abstractNote = {The alkaline-earth zirconates (CaZrO3, SrZrO3, and BaZrO3) are under active investigation as solid-state electrolytes in hydrogen fuel cells. Their performance as proton conductors depends critically on the properties of acceptor dopants. Here, we use first-principles calculations to study the role of acceptors and point defects in incorporating protons through an oxygen-vacancy-mediated process. For CaZrO3, we find that ZrCa antisites suppress formation of oxygen vacancies. Other intrinsic point defects are shown not to hinder performance. Common unintentional impurities, such as C and N, are not good acceptors but can incorporate in other configurations. Our results show that the effectiveness of common dopants such as Sc and Y is limited by self-compensation due to their incorporation on the "wrong" cation site, where they act as donors. We demonstrate that using alkali metal dopants overcomes this problem, as the formation energy of compensating donors is very high. Alkali metal dopants also have low binding energies for protons, reducing their tendency to act as traps and hence enhancing proton conductivity. As a result, our guidelines for choosing acceptor dopants and optimizing synthesis conditions can greatly improve the efficacy of these proton-conducting oxides as solid-state electrolytes.},
doi = {10.1021/acsaem.8b02222},
journal = {ACS Applied Energy Materials},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {3}
}

Journal Article:
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This content will become publicly available on March 12, 2020
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