Solid oxide ionic conductors are employed in a wide range of energy-conversion applications, such as electrolytes in fuel cells. Typically, conventional ionic conductors based on metal oxides require elevated temperatures above approximately 500 °C to activate ionic transport, but the ability to operate at lower temperature could avoid mechanical instability and operating complexities. Here we report a solid oxide proton conductor, HSrCoO2.5, which shows unusually high proton conductivity between 40 °C and 140 °C. The proton conductivity was between 0.028 S cm−1 to 0.33 S cm−1 in this temperature range, with an ionic activation energy of approximately 0.27 eV. Combining experimental results and first-principles calculations, we attribute these intriguing properties to the high proton concentration and the well-ordered oxygen vacancy channels granted by the hydrogen-intercalated brownmillerite crystalline structure. Our results open the possibility of using solid oxide materials as the proton-conducting electrolytes in low-temperature devices.
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We thank Z.-P. Shao, Y. Zhou and C.-C. Duan for helpful discussions and critical reading of the manuscript and Y. Shi and T. Liu for experimental assistance. This study was financially supported by the Basic Science Center Project of NFSC (grant number 51788104, P.Y. and C.-W.N.), the Ministry of Science and Technology of China (grant number 2021YFE0107900, P.Y.), the Beijing Nature Science Foundation (grant number Z200007, P.Y.), the National Key R&D Program of China (grant number 2021YFA1400100, S.Z., and 2021YFA1400300, P.Y.), the National Natural Science Foundation of China (grant 51872155, P.Y.), the Beijing Advanced Innovation Center for Future Chip (ICFC, P.Y. and S.Z.) and Major Science and Technology Project of Precious Metal Materials Genome Engineering in Yunnan Province (grant number 2019ZE001-1, J.W.). N.L. acknowledges support from the National Natural Science Foundation of China (grant number 11974401), CAS Project for Young Scientists in Basic Research (grant number YSBR-047) and the Strategic Priority Research Program of Chinese Academy of Sciences of China (grant number XDB33000000).
The authors declare no competing interests.
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Supplementary Figs. 1–25, Notes 1–6 and Tables 1 and 2.
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Source data for the plot in a.
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Source data for the plots in a–d.
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Lu, N., Zhang, Z., Wang, Y. et al. Enhanced low-temperature proton conductivity in hydrogen-intercalated brownmillerite oxide. Nat Energy 7, 1208–1216 (2022). https://doi.org/10.1038/s41560-022-01166-8
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