Dynamic control of oxide nanostructures is crucial for design of advanced oxide catalysts, which is also significant for understanding of the active site and reaction mechanism in oxide catalysis.

Recently, a research team led by Prof. Qiang Fu and Prof. Xinhe Bao from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) found that the reversible dynamic conversion between Cr oxide (CrO_x) nanoislands with the same thickness and CrO_x clusters with the identical size supported on Au(111) surface under different redox treatments.

This work was published in Proceedings of the National Academy of Sciences of the United States of America on May 23, 2022.

Two kinds of well-defined CrO_x nanostructures have been grown on Au(111) and unambiguously identified by scanning tunneling microscopy and theoretical calculations. The CrO_x nanoislands feature a CrO₂-bilayer (BL) structure consisting of two Cr₂O₃ monolayers bridged by one layer of O, and the CrO_x clusters have a Cr₂O₇ stoichiometry. Oxidation treatment in O₃ can disperse the CrO₂-BL nanoislands into the Cr₂O₇-dinuclear clusters, which can be dynamically converted back to the CrO₂-BL by annealing in ultrahigh vacuum.

Surface science experiments and theoretical simulations reveal that both surface oxygen atoms dissociated from O₃ and confinement effect of the Au substrate play important roles in formation of the Cr₂O₇-dinuclear clusters. The study suggests that oxide nanocatalysts with controlled size and structure can be stabilized by the specific environment and oxide-metal interface.

This work was financially supported by the National Key R&D Program of China, National Natural Science Foundation of China, and LiaoNing Revitalization Talents Program. (Text/image by Yanxiao Ning and Zhiyu Yi)

        Article link: https://www.pnas.org/doi/full/10.1073/pnas.2120716119