Highly active gold nanoparticles encapsulated in amorphous silicon oxide for CO oxidation

Gold nanoparticles encapsulated in amorphous silicon oxide (18Au@SiO₂_H₂) exhibit high catalytic activity for CO oxidation over a wide temperature range (from 203 to 673 K). Characterizations of the catalysts revealed strong interactions between slight positively charged gold nanoparticles and amorphous silicon oxide, which are responsible for the high catalytic activity. Gold nanoparticle catalysts prepared using different concentrations of the HAuCl₄ precursor and different reducing agents have been compared to determine the effects of the above parameters on the catalytic activity. Increase in the concentration of HAuCl₄ precursor, decreases the pH; in turn changes the shape of the silicon oxide even on retention of hydrocarbon groups in supports. 18Au@SiO₂_H₂ catalyst prepared with 2.0 % HAuCl_4aq was found to have the optimal support, in suggesting the change in the reaction mechanism of CO oxidation depends on the shape of the silicon oxide. This catalyst maintained high activity over a wide temperature range.