Regulating the surface Au sites of Au/TiO2 catalyst for achieving co-oxidation of HCHO and CO at room temperature

Abstract

While supported Au catalyst is active for formaldehyde (HCHO) or CO oxidation alone at room temperature, it has not been reported hitherto to efficiently catalyze co-oxidation of HCHO and CO. In this work, we prepared the fresh Au/TiO2 (Au/Ti-F) and the Au/Ti-O by pretreating Au/Ti-F at 300 °C under O2 atmosphere. The Au/Ti-F is only active for HCHO oxidation during HCHO and CO co-oxidation, while the Au/Ti-O shows high efficiency for both HCHO and CO oxidation, achieving 100 % conversions at room temperature. Detailed characterization and DFT calculation indicate that only the Au-Ti interface sites were exposed on Au/Ti-F because other Au sites on Au NPs were covered by Au(OH)n (0 <n < 3). Over Au/Ti-O, besides the active sites at the Au-Ti interface, the metallic Au sites away from the interface were formed during the high-temperature treatment. HCHO oxidation occurs at the Au-Ti interface sites while CO oxidation occurs at the metallic top Au sites; hence high activity for HCHO and CO co-oxidation was achieved over Au/Ti-O. The obtained insight into the dual Au sites will benefit future design of supported Au catalysts.