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 (CrOx) nanoislands with the same thickness and CrOx 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 CrOx nanostructures have been grown on Au(111) and unambiguously identified by scanning tunneling microscopy and theoretical calculations. The CrOx nanoislands feature a CrO2-bilayer (BL) structure consisting of two Cr2O3 monolayers bridged by one layer of O, and the CrOx 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