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Broad Applicability of Electrochemical Impedance Spectroscopy to the Measurement of Oxygen Nonstoichiometry in Mixed Ion and Electron Conductors

Huang, Ruiyun and Carr, Connor G. and Gopal, Chirranjeevi Balaji and Haile, Sossina M. (2022) Broad Applicability of Electrochemical Impedance Spectroscopy to the Measurement of Oxygen Nonstoichiometry in Mixed Ion and Electron Conductors. ACS Applied Materials & Interfaces, 14 (17). pp. 19629-19643. ISSN 1944-8244. doi:10.1021/acsami.2c05417.

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Oxygen nonstoichiometry is a fundamental feature of mixed ion and electron conductors (MIECs). In this work, a general electrochemical method for determining nonstoichiometry in thin film MIECs, via measurement of the chemical capacitance, is demonstrated using ceria and ceria-zirconia (Ce0.8Zr0.2O2−δ) as representative materials. A.C. impedance data are collected from both materials at high temperature (750–900 °C) under reducing conditions with oxygen partial pressure (pO₂) in the range 10–13 to 10–20 atm. Additional measurements of ceria-zirconia films are made under relatively oxidizing conditions with pO₂ in the range 0.2 to 10⁻⁴ atm and temperatures of 800–900 °C. Under reducing conditions, the impedance spectra are described by a simple circuit in which a resistor is in series with a resistor and capacitor in parallel, and thickness-dependent measurements are used to resolve the capacitance into interfacial and chemical terms. Under more oxidizing conditions, the impedance spectra (of Ce_(0.8)Zr_(0.2)O_(2−δ)) reveal an additional diffusional feature, which enables determination of the ionic resistance of the film in addition to the capacitance, and hence the transport properties. A generalized mathematical formalism is presented for recovering the nonstoichiometry from the chemical capacitance, without recourse to defect chemical models. The ceria nonstoichiometry values are in good agreement with literature values determined by thermogravimetric measurements but display considerably less scatter and are collected on considerably shorter time scales. The thermodynamic analysis of Ce_(0.8)Zr_(0.2)O_(2−δ) corroborates earlier findings that introduction of Zr into ceria enhances its reducibility.

Item Type:Article
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URLURL TypeDescription
Carr, Connor G.0000-0003-1494-9797
Haile, Sossina M.0000-0002-5293-6252
Additional Information:© 2022 American Chemical Society. Received 28 March 2022. Accepted 15 April 2022. Published online 25 April 2022. Published in issue 4 May 2022. This work was supported by the US Department of Energy under Office Energy Efficiency and Renewable Energy, Contract No. DE-EE0008089. Additional support was provided by the US National Science Foundation under Award No. DMR-1505103. This work made use of the Pulsed Laser Deposition Shared Facility at the Materials Research Center at Northwestern University supported by the National Science Foundation MRSEC program (DMR-1720139) and the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (ECCS-1542205). The authors declare no competing financial interest.
Funding AgencyGrant Number
Department of Energy (DOE)DE-EE0008089
Subject Keywords:oxygen nonstoichiometry; impedance spectroscopy; chemical capacitance; mixed ion and electron conductor (MIEC); ionic conductivity; ceria; ceria-zirconia
Issue or Number:17
Record Number:CaltechAUTHORS:20220520-388238000
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Official Citation:Broad Applicability of Electrochemical Impedance Spectroscopy to the Measurement of Oxygen Nonstoichiometry in Mixed Ion and Electron Conductors Ruiyun Huang, Connor G. Carr, Chirranjeevi Balaji Gopal, and Sossina M. Haile ACS Applied Materials & Interfaces 2022 14 (17), 19629-19643 DOI: 10.1021/acsami.2c05417
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114839
Deposited By: George Porter
Deposited On:20 May 2022 22:38
Last Modified:20 May 2022 22:38

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