Atomic-Resolution HAADF-STEM Study of Ag/Al2O3 Catalysts for Borrowing-Hydrogen and Acceptorless Dehydrogenative Coupling Reactions of Alcohols

We study HAADF-STEM analysis of Ag/Al 2 O 3 samples (as-calcined and reduced at 25, 300, 500 and 900 °C). Ag atoms are classified into subnanoclusters (0.3–1 nm), nanoclusters (1–3 nm), nanoparticles (3–10 nm) and polycrystals (>10 nm). The size of Ag increases with the reduction temperature, which is supported by EXAFS analysis. The effect of Ag size on the activity for borrowing-hydrogen and acceptorless dehydrogenative couplings of alcohols is discussed.