Au@Void@TiO2 yolk-shell nanostructures as catalysts for the promotion of oxidation reactions at cryogenic temperatures

摘要

A new gold-titania catalyst has been developed for cryogenic oxidations based on a yolk-shell nanoarchitecture. The synthesis of those structures involves the sequential deposition of a sacrificial silica layer and a titania shell around well-defined gold nanoparticles followed by removal of the silica via NaOH etching. The resulting catalyst contains an amorphous titania shell with sodium titanate and silicon impurities that proved critical for the cryogenic activity; removal of those via HCl treatment kills most of the catalytic conversion. Oxidation of carbon monoxide is possible with this Au@Void@TiO2 catalyst at temperatures as low as 120 K, by a mechanism different than the one operative at room temperature that involves a weakly-adsorbed CO species with a C-O stretching frequency of 2162 cm(-1), possibly at Au-TiO2 interfacial sites. (C) 2015 Elsevier B.V. All rights reserved.