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., AgOx 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 AgOx clusters in liquid water is attributed to liquid-phase Ostwald ripening through dissolution of AgOx clusters into water and subsequent redeposition to form Ag2O particles. The immersion into organic solvents such as ethanol leads to reduction of AgOx 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.