Liquid-mediated Ostwald ripening of Ag-based clusters supported on oxides

Reconstruction of supported nanocatalysts often occurs in gas–solid reactions and significantly affects the catalytic performance, yet it is much less explored in liquid-phase environment. Herein, we find that highly-dispersed Ag nanocatalysts, i.e., AgO_x clusters, supported on alumina, silica, and titania, can aggregate into larger Ag or Ag₂O particles after immersing in liquid-phase media at room temperature. The spontaneous aggregation of AgO_x clusters in liquid water is attributed to liquid-phase Ostwald ripening through dissolution of AgO_x clusters into water and subsequent redeposition to form Ag₂O particles. The immersion into organic solvents such as ethanol leads to reduction of AgO_x clusters and further growth into Ag particles. This work reveals that liquid-phase reaction media can induce substantial structural evolution of supported nanostructured catalysts, which should be carefully considered in liquid–solid interface catalytic reactions such as electrocatalysis, environmental catalysis, and organic synthesis in liquid phase.