Synergistic Effect in an Au−Ag Alloy Nanocatalyst: CO Oxidation
journal contributionposted on 13.01.2005, 00:00 by Jun-Hong Liu, Ai-Qin Wang, Yu-Shan Chi, Hong-Ping Lin, Chung-Yuan Mou
Au−Ag alloy nanoparticles supported on mesoporous aluminosilicate have been prepared by one-pot synthesis using hexadecyltrimethylammonium bromide (CTAB) both as a stabilizing agent for nanoparticles and as a template for the formation of mesoporous structure. The formation of Au−Ag alloy nanoparticles was confirmed by X-ray diffraction (XRD), ultraviolet−visible (UV−vis) spectroscopy, and transmission electron microscopy (TEM). Although the Au−Ag alloy nanoparticles have a larger particle size than the monometallic gold particles, they exhibited exceptionally high activity in catalysis for low-temperature CO oxidation. Even at a low temperature of 250 K, the reaction rate can reach 8.7 × 10-6 mol·gcat.-1·s-1 at an Au/Ag molar ratio of 3/1. While neither monometallic Au@MCM-41 nor Ag@MCM-41 shows activity at this temperature, the Au−Ag alloy system shows a strongly synergistic effect in high catalytic activity. In this alloy system, the size effect is no longer a critical factor, whereas Ag is believed to play a key role in the activation of oxygen.