Electroless deposition of Au on Ag sol: Oxidation of carbon monoxide and methanol

Ag sols were synthesised by gamma-irradiation of AgNO3 solution in presence of 2-propanol as OH radical scavenger and PVP as steric stabiliser. Different dose rates were applied to control the size of Ag particles. Ag sol prepared was applied for reduction of AuCl4− resulting in the formation of Au–Ag and Au nanoparticles as confirmed by TEM and the red shift of the surface plasmon resonance of Ag. Au–Ag nanoparticles were fixed to Al2O3 (ICN alumina N). Following O2 treatment at 673 K the Au–Ag/Al2O3 samples were tested in CO and methanol total oxidation. The increase of Ag activity at low Au concentrations can be attributed to small Au particles decorating Ag causing morphological and ligand effects.