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Electron-Phonon Renormalization in the Proton-Conducting Electrolyte BaZrO3 and Its Implications for High-Temperature Electrolysis

Shenli Zhang1,2,†, Andrew J.E. Rowberg1,2, Tadashi Ogitsu1,2, Tuan Anh Pham1,2, and Joel B. Varley1,2,*

  • *Contact author: varley2@llnl.gov
  • †Contact author: zhang52@llnl.gov
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PRX Energy 4, 013013 – Published 24 March, 2025

DOI: https://doi.org/10.1103/PRXEnergy.4.013013

Abstract

Electrical leakage is an inherent problem in solid-oxide fuel and electrolyzer cells, limiting their energy-conversion efficiency. High concentrations of electrons or holes can exacerbate this issue. However, it is largely unclear how the typical high operating temperatures of the systems influence their charge-carrier concentrations. In this work, we use first-principles calculations to examine how lattice vibrations impact electrical conductivity in conventional electrolytes, using BaZrO3 as a representative material. Our analysis shows that phonon-induced shifts in the band gap and band edges lead to a dramatic increase in p-type carrier concentrations at temperatures above 600 K, compared to models that neglect temperature effects. Additionally, we reveal the importance of oxygen-ion motion on band-edge positions, which makes valence-band-edge shift dominate the band-gap change. Our study provides a protocol for calculating phonon-induced changes in similar oxides, paving the way for interrogating electrical leakage in electrolytes for high-temperature operation.

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Popular Summary

Solid oxide electrolyzer cells provide a highly efficient route for the electrochemical conversion of steam to hydrogen or the use of hydrogen to generate energy in fuel-cell mode. These electrolyzers are an integral piece for realizing a future reliant upon green hydrogen. An inherent problem that limits the energy conversion efficiencies of these devices is electrical leakage, which is exacerbated by the high concentrations of electronic carriers. However, it is largely unclear how the high operating temperatures typical for these devices influence their charge carrier concentrations.

Here the authors use first-principles calculations to examine how lattice vibrations impact electrical conductivity in conventional electrolytes, using BaZrO$_3$ as a representative material. The analysis shows that phonon-induced shifts in the band gap and band edges lead to a dramatic increase in $p$-type carrier concentrations at temperatures above 600 K, compared to models that neglect temperature effects. This study provides a protocol for calculating phonon-induced changes in similar oxides, paving the way for interrogating electrical leakage in solid oxide electrolyzer and fuel cell electrolytes for high-temperature operation.

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References (77)

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PRX Energy 4, 013013– Published 24 March, 2025
  • Received 24 October 2024
  • Revised 14 January 2025
  • Accepted 18 February 2025
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