Gold nanoparticles supported on mesoporous iron oxide for enhanced CO oxidation reaction

Herein, we report the synthesis of gold (Au)-loaded mesoporous iron oxide (Fe₂O₃) as a catalyst for both CO and NH₃ oxidation. The mesoporous Fe₂O₃ is firstly prepared using polymeric micelles made of an asymmetric triblock copolymer poly(styrene-b-acrylic acid-b-ethylene glycol) (PS-b-PAA-b-PEG). Owing to its unique porous structure and large surface area (87.0 m² g^-1), the as-prepared mesoporous Fe₂O₃ can be loaded with a considerably higher amount of Au nanoparticles (Au NPs) (7.9 wt%) compared to the commercial Fe₂O₃ powder (0.8 wt%). Following the Au loading, the mesoporous Fe₂O₃ structure is still well-retained and Au NPs with varying sizes of 3-10 nm are dispersed throughout the mesoporous support. When evaluated for CO oxidation, the Au-loaded mesoporous Fe₂O₃ catalyst shows up to 20% higher CO conversion efficiency compared to the commercial Au/Fe₂O₃ catalyst, especially at lower temperatures (25-150 °C), suggesting the promising potential of this catalyst for low-temperature CO oxidation. Furthermore, the Au-loaded mesoporous Fe₂O₃ catalyst also displays a higher catalytic activity for NH₃ oxidation with a respectable conversion efficiency of 37.4% compared to the commercial Au/Fe₂O₃ catalyst (15.6%) at 200 °C. The significant enhancement in the catalytic performance of the Au-loaded mesoporous Fe₂O₃ catalyst for both CO and NH₃ oxidation may be attributed to the improved dispersion of the Au NPs and enhanced diffusivity of the reactant molecules due to the presence of mesopores and a higher oxygen activation rate contributed by the increased number of active sites, respectively.