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.