Size-Dependent Restructuring of Supported Platinum Cluster Catalysts

Supported metal clusters have reactivities that depend on their nuclearity and structure. Herein, we present a strategy for precisely controlling the nuclearity of platinum clusters and demonstrate their size-dependent restructuring behavior and catalytic properties. The clusters are located on isolated CeO_x nanoislands on high-area SiO₂, and the isolation facilitates control of the migration of the platinum. Thus, in an H₂ atmosphere, the clusters are stably confined to the nanoislands, whereas in a CO atmosphere, they migrate out of the nanoislands, grow, and are thereafter confined again to the nanoislands. During CO oxidation catalysis, these platinum clusters undergo restructuring. Clusters with average diameters of 0.7 nm are quickly deactivated as O₂ causes oxidative fragmentation to form single atoms. In contrast, 1.5 nm clusters maintain their nuclearity, with only partial surface oxidation, being more active as catalysts than both the 0.7 nm clusters and those with 2.2 nm diameters. These results provide new insights into the dynamic restructuring of catalytically active metal clusters and how to construct and stabilize supported metal cluster catalysts with optimized properties.