Abstract
Proton ceramic electrochemical cells PCECs hold promise for efficient, sustainable production and use of hydrogen. The positive electrodes are mixed proton conducting perovskites that facilitate water splitting and oxygen reduction, but the factors that determine the protonation are poorly understood. Here, we establish the governing principles of protonation through a study of hydration of 45 double perovskites with the general formula \({A}^{{{{\rm{I}}}}}{A}^{{{{\rm{II}}}}}{{{{\rm{Co}}}}}_{2}{{{{\rm{O}}}}}_{6-\delta }\), having Ba or Ba+Sr on AI and a mix of rare earths (Y and lanthanides Ln = La, Pr, Nd, Sm, Gd, Dy, Tb, Lu) on AII. We show how hydration is coupled to the A-site basicity and disorder as well as population of electron holes in the Co-O bond (Co oxidation state), promoted by a closed or semi-closed Ln 4 f shell, i.e., Ln = La, Gd, Lu.
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Acknowledgements
This work is financed by The Research Council of Norway (Grant nᵒ 272797 “GoPHy MiCO” and nᵒ 299736 “FunKeyCat”) through the M-ERA.NET Joint Call 2016 and 2018 (R.S., M.H.S., T.N.). Project “FunKeyCat” is supported by the National Science Centre, Poland, under the M-ERA.NET 2, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no 685451 (2016/22/Z/ST5/00691) (S.L.W., A.M.G., M.G.), and the Spanish Government through the National Research Agency AEI (grant PCIN-2017-125) (M.B., J.A.S.). This publication was partially developed under the provision of the Polish Ministry and Higher Education project “Support for research and development with the use of research infrastructure of the National Synchrotron Radiation Centre SOLARIS” under contract nr 1/SOL/2021/2 (S.L.W., A.M.G., M.G.). We acknowledge the SOLARIS Centre for access to the Beamline PIRX, where the measurements were performed. We thank Dr. Marcin Zając for assistance (proposal nos. 191011 and 201036). We also thank Dr. Vegar Øygarden for Rietveld refinements of NPD data.
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R.S.: Conceptualisation (lead), data curation (equal), formal analysis (equal), funding acquisition (lead), investigation (equal), methodology (equal), project administration (lead), supervision, validation (lead), visualisation (lead), writing original draft (lead). T.N.S.: Investigation – SIMS measurements on BGLC82. L.V.: Investigation – SIMS measurements on BGLC37. P.A.C.: Investigation – STEM-EDS. M.H.S.: SR-PXD and NPD, data curation (equal), formal analysis (equal), funding acquisition (equal), investigation (equal), methodology (equal). S.L.W.: Formal analysis (equal), funding acquisition (equal), investigation (equal), methodology (equal), project administration (equal), supervision, validation (equal), writing (equal). I.S.: Formal analysis (equal), investigation (equal), methodology (equal), validation (equal). A.M.G.: Formal analysis (equal), funding acquisition (equal), investigation (equal), methodology (equal), project administration (equal), supervision, validation (equal). M.B.: Formal analysis (equal), funding acquisition (equal), investigation (equal), methodology (equal), project administration (equal), supervision, validation (equal). T.N., M.G. and J.M.S.: funding acquisition (equal), investigation (equal), methodology (equal), project administration (equal), supervision, Writing – Review & Editing.
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Strandbakke, R., Wachowski, S.L., Balaguer, M. et al. Governing principles of hydration of mixed proton conducting Co-based double perovskites. Nat Commun (2026). https://doi.org/10.1038/s41467-026-70212-w
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DOI: https://doi.org/10.1038/s41467-026-70212-w
