High-Entropy A-Site Disorder Enhances Oxygen Evolution Reaction Activity and Stability in Nickelate Thin Films

Abstract

Rare-earth nickelates are among the most active oxide electrocatalysts for the oxygen evolution reaction (OER), owing to their tunable Ni-O covalency, near-unity eg occupancy, and sensitivity to A-site chemistry, oxygen stoichiometry, and epitaxial strain. Here, we use epitaxial A-site high-entropy (La0.2Pr0.2Nd0.2Sm0.2Eu0.2)NiO3 thin films to reveal how epitaxial strain influences defect formation, Ni valence, electronic structure, and OER activity in a chemically disordered rare-earth (RE) sublattice. Tensile strain promotes Ruddlesden-Popper fault formation, interrupts the corner-sharing NiO6 network, and lowers the average Ni oxidation state. Although the occupied density of states near the Fermi level remains largely unchanged, O K-edge X-ray absorption spectroscopy reveals increased low-energy unoccupied states under tensile strain. First-principles calculations suggest that tensile strain shifts RE 4f-derived states toward the Fermi level, enhancing RE 4f-O 2p-Ni 3d hybridization. These coupled structural and electronic changes lead to earlier OER onset, stronger pre-catalytic Ni redox features, and higher activity than compressively strained films and representative single-A-site nickelates. The high-entropy nickelate also shows enhanced resistance to OER-induced structural degradation compared with LaNiO3. These results suggest that A-site configurational disorder and epitaxial strain can jointly tune defect formation and rare-earth-derived electronic states, providing a route for improving perovskite oxide electrocatalysts.

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BibTeX RIS

BibTeX

@misc{choi2026highentropy,
  title = {{High-Entropy A-Site Disorder Enhances Oxygen Evolution Reaction Activity and Stability in Nickelate Thin Films}},
  author = {Min-Ju Choi and Le Wang and Krishna Prasad Koirala and Hyoju Park and Mark E. Bowden and Elizabeth Helen Krenkel and Aiping Chen and Jueli Shi and Conan Weiland and Iradwikanari Waluyo and Adrian Hunt and Peter V. Sushko and Yingge Du},
  howpublished = {arXiv},
  year = {2026},
  month = nov,
  doi = {10.48550/arxiv.2611.02796},
  eprint = {2611.02796},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2611.02796},
  note = {CC BY-NC-ND 4.0},
}

RIS

TY  - UNPB
TI  - High-Entropy A-Site Disorder Enhances Oxygen Evolution Reaction Activity and Stability in Nickelate Thin Films
AU  - Min-Ju Choi
AU  - Le Wang
AU  - Krishna Prasad Koirala
AU  - Hyoju Park
AU  - Mark E. Bowden
AU  - Elizabeth Helen Krenkel
AU  - Aiping Chen
AU  - Jueli Shi
AU  - Conan Weiland
AU  - Iradwikanari Waluyo
AU  - Adrian Hunt
AU  - Peter V. Sushko
AU  - Yingge Du
PY  - 2026
DA  - 2026/11/02
PB  - arXiv
DO  - 10.48550/arxiv.2611.02796
UR  - https://arxiv.org/abs/2611.02796
AB  - Rare-earth nickelates are among the most active oxide electrocatalysts for the oxygen evolution reaction (OER), owing to their tunable Ni-O covalency, near-unity eg occupancy, and sensitivity to A-site chemistry, oxygen stoichiometry, and epitaxial strain. Here, we use epitaxial A-site high-entropy (La0.2Pr0.2Nd0.2Sm0.2Eu0.2)NiO3 thin films to reveal how epitaxial strain influences defect formation, Ni valence, electronic structure, and OER activity in a chemically disordered rare-earth (RE) sublattice. Tensile strain promotes Ruddlesden-Popper fault formation, interrupts the corner-sharing NiO6 network, and lowers the average Ni oxidation state. Although the occupied density of states near the Fermi level remains largely unchanged, O K-edge X-ray absorption spectroscopy reveals increased low-energy unoccupied states under tensile strain. First-principles calculations suggest that tensile strain shifts RE 4f-derived states toward the Fermi level, enhancing RE 4f-O 2p-Ni 3d hybridization. These coupled structural and electronic changes lead to earlier OER onset, stronger pre-catalytic Ni redox features, and higher activity than compressively strained films and representative single-A-site nickelates. The high-entropy nickelate also shows enhanced resistance to OER-induced structural degradation compared with LaNiO3. These results suggest that A-site configurational disorder and epitaxial strain can jointly tune defect formation and rare-earth-derived electronic states, providing a route for improving perovskite oxide electrocatalysts.
ER  -

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