Thermal stability and catalytic activity of gold nanoparticles supported on silica

Fluxionality of gold nanoparticles investigated by Born-Oppenheimer molecular dynamics

“…An interesting theoretical basis for the nobility of gold has been given by Hammer and Nørskov based on electronic structure calculations [24], while other theoretical and experimental studies have investigated the origin of the decrease of nobility of gold [25,26]. Several studies have been published that aim at understanding the origin of the special reactivity of nano-sized gold particles towards oxygen [21,25,[27][28][29][30][31][32][33][34], but one of the keys to the understanding of the peculiar reactivity of small gold clusters lies in its fluxional character, since structural isomers are in principle able to adapt their structures towards the most favorable free-energy path [25,35].…”

Gold, an alternative to platinum group metals in automobile catalytic converters

“…An Au/SiO 2 catalyst was prepared by growing 2.5 nm GNPs on a fused silica support using the physical vapour deposition technique of magnetron sputtering. The resulting catalyst was thermally stable up to at least 500°C when annealed in an oxygen containing environment [84]. This high thermal stability was attributed to the absence of residual impurities, ensured by the halide-free production method and a strong bond (about 3 eV per bond, estimated by density functional theory calculations) between gold and defects at the silica surface.…”

“…The Au/SiO 2 catalyst has been found to be less active for CO oxidation than Au/TiO 2 catalysts. However, it can be regenerated far more easily, thus allowing full recovery of its activity after deactivation [84]. The addition of different metal oxides (MO x ) to Au/Al 2 O 3 catalysts, used for the total oxidation of methane, has shown that MO x stabilise GNPs on Al 2 O 3 and the resulting catalysts are thermally resistant up to 700°C [59].…”

Understanding Catalyst Stability through Aberration-Corrected STEM

“…However, the reaction rates produced by these materials are notoriously varied due to the large number of variables that influence the properties [8]. Using the magnetron sputtering technique and the sensitivity provided by aberration-corrected STEM we were able to probe some of these variables and uncover the important role that surface hydroxyl groups play in the stability of supported metal catalysts [6].Gold nanoparticles grown on silica were found to be very stable, even when heated to relatively high temperatures [5]. Gold catalysts grown by sputtering on fumed titania were found to be unstable, with particles that were initially in the 2-3 nm size range agglomerating into large ~20 nm particles over a few days at ambient conditions ( Figure 1).…”

“…We have recently developed a magnetron sputtering technique, able to produce a variety of catalyst materials, which allow us to investigate the factors that affect the stability of supported nanoparticle catalysts. We have produced metal nanoparticles on a range of different and industrially relevant materials including, alumina, silica, titania, and other oxides, and are able to use the same method irrespective of the surface isoelectric point [4][5][6]. This combination of novel growth techniques and aberration-corrected STEM appears able to provide an unprecedented view into the growth and stability of supported nanoparticle catalysts.…”