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Water interactions with oxygen-de cient cerium dioxide (CeO2) surfaces are central to hydrogen production and catalytic redox reactions, but the atomic-scale details of how defects influence adsorption and reactivity remain elusive. Here, we unveil how water adsorbs on partially reduced CeO2−x(111) using atomic force microscopy (AFM) with chemically sensitive, oxygen-terminated probes, combined with first-principles calculations. Our AFM imaging reveals water molecules as sharp, asymmetric boomerang-like features radically departing from the symmetric triangular motifs previously attributed to molecular water. Strikingly, these features localize near subsurface defects. While the experiments are carried out at cryogenic temperatures, water was dosed at room temperature, capturing configurations relevant to initial adsorption events in catalytic processes. Density functional theory identifies Ce3+ sites adjacent to subsurface vacancies as the thermodynamically favored adsorption sites, where defect-induced symmetry breaking governs water orientation. Force spectroscopy and simulations further distinguish Ce3+ from Ce4+ centers through their unique interaction signatures. By resolving how subsurface defects control water adsorption at the atomic scale, this work demonstrates the power of chemically selective AFM for probing site-specific reactivity in oxide catalysts, laying the groundwork for direct investigations of complex systems such as single-atom catalysts, metal-support interfaces, and defect-engineered oxides.

Rights:

• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

Keyword: scanning probe microscopy, cerium dioxide, water, surface, thin films, density functional theory

Date published: 2026-01-23

Publisher: Springer Science and Business Media LLC

Journal:

• Communications Materials (ISSN: 26624443) vol. 7 issue. 1 39

Funding:

• NIMS AG2030 (Advanced Characterization for Materials Innovation)
• NIMS AM2100 (地方連携創出)
• Japan Society for the Promotion of Science 19H05789 (Functional Surface Core Analysis: New Materials Science on Nanoscale Structures and Functions of Crystal Defect Cores)
• Japan Society for the Promotion of Science 21H01812 (Study of Catalytic Activity of Anatase TiO2 and its Nano-cluster Using Atomic Force Microscopy)
• Japan Society for the Promotion of Science 21K18876 (Ultrafast Atomic Force Microscopy Imaging of Phase Transition Phenomena on Ice Surface by Machine Learning)
• Japan Society for the Promotion of Science 22H00285 (Development of high precision on-surface reaction and study of the magnetic property in carbon nanostructures)
• Japan Society for the Promotion of Science 23KJ1516 (Clarification of Water-Gas-Shift Reaction on Cerium Dioxide surface by using Non-Contact Atomic Force Microscopy)
• Japan Society for the Promotion of Science 24K01350 (Atomic scale reactivity of small islands of a bimetallic alloy on ceria to small molecules investigated by ultrahigh resolution atomic force microscopy)

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1038/s43246-025-01011-x

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Updated at: 2026-02-08 08:30:20 +0900

Published on MDR: 2026-02-07 17:34:49 +0900