Selective Fe Promotion on Au Nanoparticles: An Efficient Way to Activate Au/SiO2 Catalysts for the CO Oxidation Reaction

The fabrication of the metal-metal oxide interface for the design and preparation of heterogeneous catalysts has been widely considered. In this work, a simple, aqueous-phase Fe promotion strategy was studied on an inactive Au/SiO2 model catalyst to generate an active Au-FeOx interface for the CO oxidation. We found that the addition of either Fe2+ or Fe3+ led to significantly higher activity if the Au NPs were already deposited on the SiO2 compared to a prepromotion of the bare support. Combining X-ray diffraction, elemental analysis, transmission electron microscopy and energy dispersive X-ray spectroscopy characterizations with the CO oxidation tests, we proved that the postpromotion strategy could more efficiently fabricate the Au-Fe interface, which after a proper thermal pretreatment could transform to the catalytically active Au-FeOx interface. The formation of such Au-Fe species interface was ascribed to the selective accumulation of the Fe3+ hydrolysis products on the Au nanoparticles (NPs), driven both by a heterogeneous nucleation/growth mechanism and a direct electrostatic adsorption mechanism.