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Cerium dioxide (CeO2) is extensively studied due to its exceptional redox properties, which are closely related to oxygen vacancy formation and the associated charging of cerium atoms from Ce4+ to Ce3+. These charged species play an important role in promoting active sites in CeO2-based catalysts. The existence of Ce3+ atoms is typically characterized by means of surface spectroscopic techniques, because the direct atomic-scale observation and discrimination of Ce3+ ions from Ce4+ atoms remains challenging. Here, we use simultaneous scanning tunneling microscopy (STM) and atomic force microscopy (AFM) complemented by force spectroscopy to characterize candidates to Ce3+ atoms on partially reduced CeO2(111) samples. While STM images reveal electronic modulations of the atomic contrast in the form of an inhomogeneous shading, AFM clearly differentiates these electronic features from the true topographic atomic structure. The chemical reactivity of these candidates to Ce3+ atoms is quantified against the Ce4+ counterparts by means of force spectroscopy using carbon monoxide functionalized probes. This study demonstrates that the combination of STM with AFM and force spectroscopy bears great potential to provide robust atomic-level insights into the chemistry of defects at ceria surfaces.

Rights:

• Creative Commons BY-NC Attribution-NonCommercial 4.0 International
  

Keyword: Metal oxide surface, ceria, scanning tunneling microscopy, atomic force microscopy;, force spectroscopy, Ce3+

Date published: 2025-12-31

Publisher: Informa UK Limited

Journal:

• Science and Technology of Advanced Materials (ISSN: 14686996) vol. 26 issue. 1 2528596

Funding:

• The National Institute for Materials Science AG2030
• The Ministry of Education, Culture, Sports, Science and Technology of Japan 19H05789
• The Ministry of Education, Culture, Sports, Science and Technology of Japan 21H01812
• The Ministry of Education, Culture, Sports, Science and Technology of Japan 21K18876
• The Ministry of Education, Culture, Sports, Science and Technology of Japan 22H00285
• The Ministry of Education, Culture, Sports, Science and Technology of Japan 24K01350
• The Ministry of Education, Culture, Sports, Science and Technology of Japan 24K21716
• JSPS DC1 fellowship 23KJ1516
• The National Institute for Materials Science AM2100

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

MDR DOI:

First published URL: https://doi.org/10.1080/14686996.2025.2528596

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Updated at: 2025-08-19 12:30:24 +0900

Published on MDR: 2025-08-19 12:21:33 +0900