Resolving the puzzle of single-atom silver dispersion on nanosized γ-Al2O3 surface for high catalytic performance

Ag/gamma-Al2O3 is widely used for catalyzing various reactions, and its performance depends on the valence state, morphology and dispersion of Ag species. However, detailed anchoring mechanism of Ag species on gamma-Al2O3 remains largely unknown. Herein, we reveal that the terminal hydroxyls on gamma-Al2O3 are responsible for anchoring Ag species. The abundant terminal hydroxyls existed on nanosized gamma-Al2O3 can lead to single-atom silver dispersion, thereby resulting in markedly enhanced performance than the Ag cluster on microsized gamma-Al2O3. Density-functional-theory calculations confirm that Ag atom is mainly anchored by the terminal hydroxyls on (100) surface, forming a staple-like local structure with each Ag atom bonded with two or three terminal hydroxyls. Our finding resolves the puzzle on why the single-atom silver dispersion can be spontaneously achieved only on nanosized gamma-Al2O3, but not on microsized gamma-Al2O3. The obtained insight into the Ag species dispersion will benefit future design of more efficient supported Ag catalysts.