Abstract
Two-step thermochemical cycles offer a clean route for hydrogen and oxygen production but are typically limited to high temperatures exceeding 1500 °C. Lowering operating temperatures would enable the use of alternative heat sources such as industrial waste heat. Here, we report Pr3ZrO8 as a new enabling material for efficient intermediate-temperature redox cycling, with thermal reduction at 900 °C in argon and steam oxidation at 400 °C. Pr3ZrO8 adopts a face-centered cubic structure similar to CeO2 but exhibits significantly greater oxygen deficiency, achieving average oxygen and hydrogen fluxes of 331.7 and 70.3 µmol·g-1, respectively, over ten cycles at 20%H₂O. These values surpass those of leading CeO2₋δ and perovskite oxides under comparable or more severe conditions. In-situ neutron and X-ray diffraction determine the phase stability boundaries of Pr3ZrO8, while density functional theory identifies O-H bond cleavage as the rate-limiting step. These results establish Pr3ZrO8 as a promising material for intermediate-temperature thermochemical oxygen and hydrogen production.
Data availability
The experimental data generated in this study have been deposited in Zenodo (https://doi.org/10.5281/zenodo.17427370) for easy access. Data are available from the corresponding authors upon request.
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Acknowledgements
Kevin Huang would like to thank the South Carolina SmartState Endowment Program for supporting this exploratory work. Xueling Lei thanks the National Natural Science Foundation of China (Grant No. 12164020) for financial support and the Hefei Advanced Computing Center for computational support. S.M. would like to acknowledge the startup fund from the University of South Carolina. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The beam time was allocated to VULCAN (Y.C. and K.A.) on proposal numbers IPTS-27973 and IPTS-32446. This work also used the Expanse supercomputer at the San Diego Supercomputer Center through allocation PHY230093 (S.M.) from the Advanced Cyberinfrastructure Coordination Ecosystem: Services & Support (ACCESS) program, which is supported by National Science Foundation Grants No. 2138259, No. 2138286, No. 2138307, No. 2137603, and No. 2138296. Open Access funding is made possible by South Carolina SmartState Endowment Program.
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K.H. conceived the concept, designed the experiments and revised manuscript; X.L. analyzed the data and performed writing of the simulation section; L.C. performed DFT calculations; J.L. drafted the manuscript; J.L. and Y.Z. synthesized materials; J.L., Y.C., and K.A. performed VTND and analyzed the data; J.L. conducted other materials characterization, tested TC performance, and analyzed data; Y.S. and X.J. performed defect chemistry modeling; Z.W. and S.M. calculated defect formation energy.
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Lu, J., Zhang, Y., Chen, L. et al. A new highly oxygen-deficient and cubic Pr3ZrO8-δ for intermediate-temperature thermochemical production of oxygen and hydrogen. Nat Commun (2026). https://doi.org/10.1038/s41467-026-69235-0
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DOI: https://doi.org/10.1038/s41467-026-69235-0
