Highly-Loaded Ag Clusters Prepared by Flame Synthesis

Abstract

Ag particles supported on a metal oxide support have been used for various catalytic reactions (e.g. selective oxidation of ethylene). To improve the catalytic activity, size reduction of Ag particles is desired. However, it is challenging to obtain small Ag particles due to the low Tammann temperature of Ag. In this study, we successfully deposited 20 wt% of Ag clusters (~2 nm) onto TiO₂ using flame spray pyrolysis. The Ag clusters were stabilized by strong metal-support interaction (SMSI) between Ag and TiO₂ which was induced in the combustion reaction zone. SMSI formed TiOx as confirmed by X-ray diffraction. The amount of TiOx depended on the flame conditions and Ag content (10–40 wt%). The surface area of Ag clusters was estimated by H₂ pulse titration. The Ag surface area increased with Ag content up to 20 wt%, and by further increasing the Ag content to 40 wt%, the surface area did not change. The stability of Ag clusters depended on the Ag content, the flame conditions, and the specific surface area of the titanium oxide support. In the future, we will explore catalytic activity of FSP-made Ag clusters for some reactions.