Kim Kyungmin, Abe Masayuki, Kawai Shigeki, Custance Oscar
Graduate School of Engineering Science, Osaka University, Toyonaka, Japan.
Center for Basic Research on Materials, National Institute for Materials Science, Tsukuba, Japan.
Sci Technol Adv Mater. 2025 Jul 4;26(1):2528596. doi: 10.1080/14686996.2025.2528596. eCollection 2025.
Cerium dioxide (CeO ) 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 Ce to Ce . These charged species play an important role in promoting active sites in CeO -based catalysts. The existence of Ce atoms is typically characterized by means of surface spectroscopic techniques, because the direct atomic-scale observation and discrimination of Ce ions from Ce atoms remains challenging. Here, we use simultaneous scanning tunneling microscopy (STM) and atomic force microscopy (AFM) complemented by force spectroscopy to characterize candidates to Ce atoms on partially reduced CeO (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 Ce atoms is quantified against the Ce 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.
二氧化铈（CeO₂）因其特殊的氧化还原性质而受到广泛研究，这些性质与氧空位的形成以及铈原子从Ce³⁺到Ce⁴⁺的相关电荷变化密切相关。这些带电物种在促进基于CeO₂的催化剂中的活性位点方面起着重要作用。Ce³⁺原子的存在通常通过表面光谱技术来表征，因为直接在原子尺度上观察和区分Ce³⁺离子与Ce⁴⁺原子仍然具有挑战性。在这里，我们使用同步扫描隧道显微镜（STM）和原子力显微镜（AFM），并辅以力谱技术，来表征部分还原的CeO₂（111）样品上Ce³⁺原子的候选物。虽然STM图像以不均匀阴影的形式揭示了原子对比度的电子调制，但AFM清楚地将这些电子特征与真实的地形原子结构区分开来。通过使用一氧化碳功能化探针的力谱技术，将这些Ce³⁺原子候选物与Ce⁴⁺对应物的化学反应性进行了量化。这项研究表明，STM与AFM和力谱技术的结合具有巨大潜力，能够为氧化铈表面缺陷的化学性质提供可靠的原子级见解。
