Enhanced oxygen activation on an atomically dispersed Au catalyst with dual active sites for room-temperature formaldehyde oxidation

Abstract

Formaldehyde (HCHO) is known to be a hazardous indoor air pollutant. Noble metal catalysts offer a feasible approach for indoor HCHO decomposition. Oxygen activation via a noble metal such as gold plays a critical role in realizing the total HCHO oxidation, but then it is vague how different-sized noble metals function synergistically on oxygen activation. Here, an Au/CeO₂ catalyst with atomically dispersed Au (Au/CeO₂-550) was successfully prepared through a thermal aging treatment, and a synergistic mechanism for the HCHO oxidation reaction involving co-loading of single Au atoms and Au nanoclusters on CeO₂ was revealed. Strikingly, the HCHO oxidation performance of the obtained Au/CeO₂-550 catalyst at room temperature was significantly greater than that of other Au/CeO₂ catalysts, which was attributed to a concerted catalysis mechanism of the individual Au atoms and nanoclusters. The surface oxygen species of CeO₂ activated by single Au atoms can promptly transform HCHO into dioxymethylene species, while Au nanoclusters well adsorb and activate molecular oxygen to oxidize the dioxymethylene into formate, which is further oxidized into carbonates, and the carbonates are eventually decomposed into CO₂ and H₂O. This synergy results in enhanced HCHO oxidation at surface sites between neighboring single Au atoms and Au nanoclusters.