Abstract
Gold nanoparticles on transition-metal oxides were synthesized by two different methods: precipitation and photoinduced decomposition of an intermediate gold–azido complex. Only samples prepared by the precipitation method showed significant CO conversion at low temperature. XPS shows the formation of two Au species (Au0 and Auδ+) on the surface of active Au/TiO2 and Au/Fe2O3 samples. The energy shift of the Auδ+ peak depends on the support and is 0.6 and 0.9 eV for Au/TiO2 and Au/Fe2O3, respectively. TEM images indicate the formation of overlayer on Au particles. These results prove Au activation via a strong metal–support interaction, on the basis of the strong influence of the support on the electronic structure of the gold through charge transfer and stabilization of low-coordinated Au atoms.
Highlights
It should be stressed that the presence of such proposed active sites for molecular oxygen dissociation does not prevent the disappearance of the Au-oxide when O3 is removed at 100°C
This observation suggests that low-coordinated Au sites alone might not dissociate molecular oxygen as efficiently at room temperature [32,95] or the number of active sites was not sufficient to compensate for the thermal decomposition of the oxide, unlike the case of O3 dissociation
Whereas the restructuring remains upon lowering the chemical potential of oxygen to vacuum levels, the absorbed oxygen species and the surface oxide vanish even at 100°C indicating that the heat of adsorption and heat of formation respectively are small even in the presence of the massive restructuring
Summary
Gold settles at the bottom of patience.
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