Atomic-Level Design and Understanding of Hydroxyl-Mediated Ag Sites with Catalytic Versatility.

Regulating the size of active centers in catalysts exerts a profound effect on their activity and selectivity. Here, we demonstrate a strategy for precise control over the size of Ag species on Al2O3, enabling the 2%Ag/Al2O3 catalyst to be tailored for various catalytic reactions. Building on the mechanism wherein hydroxyl groups serve as anchoring sites for Ag, we synthesized hydroxyl-rich Al2O3 supports and subsequently reduced the hydroxyl content through roasting. This approach allowed Ag species to exist on the Al2O3 surface as isolated atoms, clusters, or nanoparticles. As the Ag size increased from single atoms to clusters and nanoparticles, the catalyst's O2 activation ability was progressively enhanced, leading to significant performance variations in the O2-involved reactions. Notably, the synthesis of this hydroxyl-rich support is facile and reproducible. Our findings offer valuable insights into the rational design of supported Ag catalysts with controllable active center sizes for diverse catalytic applications.