Dynamic transformation between bilayer islands and dinuclear clusters of Cr oxide on Au(111) through environment and interface effects

Dynamic control of oxide nanostructures is crucial for the design of advanced oxide catalysts, which is also significant for understanding the active site and reaction mechanism in oxide catalysis. Here, we demonstrate reversible dynamic conversion between Cr oxide (CrO(x)) nanoislands with the same thickness and CrO(x) clusters with identical size supported on an Au(111) surface under different redox treatments. The CrO(x) nanoislands feature a CrO(2) bilayer (BL) structure consisting of two Cr(2)O(3) monolayers bridged by one layer of O, and the CrO(x) clusters have a Cr(2)O(7) stoichiometry. Oxidation treatment in O(3) can disperse the CrO(2) BL nanoislands into the Cr(2)O(7) dinuclear clusters, which can be dynamically converted back to the CrO(2) BL by annealing in ultrahigh vacuum. Surface science experiments and theoretical simulations reveal that both surface oxygen atoms dissociated from O(3) and the confinement effect of the Au substrate play important roles in formation of the Cr(2)O(7) dinuclear clusters. This study suggests that oxide nanocatalysts with controlled size and structure can be stabilized by the specific environment and the oxide–metal interface.