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Oxygen affinity: the missing link enabling prediction of proton conductivities in doped barium zirconates

Yamazaki, Yoshihiro and Kuwabara, Akihide and Hyodo, Junji and Okuyama, Yuji and Fisher, Craig A. J. and Haile, Sossina M. (2020) Oxygen affinity: the missing link enabling prediction of proton conductivities in doped barium zirconates. Chemistry of Materials, 32 (17). pp. 7292-7300. ISSN 0897-4756. https://resolver.caltech.edu/CaltechAUTHORS:20200731-105314178

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Abstract

Proton-conducting oxides, specifically doped barium zirconates, have garnered much attention as electrolytes for solid-state electrochemical devices operable at intermediate temperatures (400–600 °C). In chemical terms, hydration energy, E_(hyd), and proton–dopant association energy, E_(as), are two key parameters that determine whether an oxide exhibits fast proton conduction, but to date ab initio studies have for the most part studied each parameter separately, with no clear correlation with proton conductivity identified in either case. Here, we demonstrate that the oxygen affinity, E_(O.dopant), defined as the energy released when an oxide ion enters an oxygen vacancy close to a dopant atom, is the missing link between these two parameters and correlates well with experimental proton conductivities in doped barium zirconates. Ab initio calculations of point defects and their complexes in Sc-, In-, Lu-, Er-, Y-, Gd-, and Eu-doped barium zirconates are used to determine E_(hyd), E_(as), E_(O.dopant), and the hydrogen affinity, EH.host, of each system. These four energy terms are related by E_(hyd) = E_(O.dopant) + 2E_(H.host) + 2E_(as). Complementary impedance spectroscopy measurements reveal that the stronger the calculated oxygen affinity of a system, the higher the proton conductivity at 350 °C. Although the proton trapping site is also an important factor, the results show that oxygen affinity is an excellent predictor of proton conductivity in these materials.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1021/acs.chemmater.0c01869DOIArticle
ORCID:
AuthorORCID
Haile, Sossina M.0000-0002-5293-6252
Additional Information:© 2020 American Chemical Society. Received: May 4, 2020; Revised: July 29, 2020; Published: July 30, 2020. This work was supported by JSPS KAKENHI (JP15H02287, JP16H00891, and JP18H01694), Iketani Foundation, Kyushu University Progress 100, and the Japan Science and Technology Agency CREST (JPMJCR18J3). A.K. acknowledges financial support from JSPS KAKENHI (JP25106008, JP16K06739 and JP16H06440), and S.M.H. acknowledges support from the US Department of Energy (under award DE-AR0000498). We thank J. Potticary for assistance with Er-doped BaZrO3 synthesis and Dr. K. Yamamoto for assistance with silver electrode sputtering. The authors declare no competing financial interest.
Funders:
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)15H02287
Japan Society for the Promotion of Science (JSPS)16H00891
Japan Society for the Promotion of Science (JSPS)JP18H01694
Iketani FoundationUNSPECIFIED
Kyushu UniversityUNSPECIFIED
Japan Science and Technology AgencyJPMJCR18J3
Japan Society for the Promotion of Science (JSPS)25106008
Japan Society for the Promotion of Science (JSPS)16K06739
Japan Society for the Promotion of Science (JSPS)16H06440
Department of Energy (DOE)DE-AR0000498
Issue or Number:17
Record Number:CaltechAUTHORS:20200731-105314178
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200731-105314178
Official Citation:Oxygen Affinity: The Missing Link Enabling Prediction of Proton Conductivities in Doped Barium Zirconates. Yoshihiro Yamazaki, Akihide Kuwabara, Junji Hyodo, Yuji Okuyama, Craig A. J. Fisher, and Sossina M. Haile. Chemistry of Materials 2020 32 (17), 7292-7300 DOI: 10.1021/acs.chemmater.0c01869
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104676
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:31 Jul 2020 18:08
Last Modified:11 Sep 2020 17:39

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