The adhesion and shape of nanosized Au particles in a Au/TiO2 catalyst

Catalytically Active Gold: From Nanoparticles to Ultrathin Films

“…46,[57][58][59][60][61][62] Catalytically Active Gold Chen and Goodman ν CO frequencies, or the extent of the electron-rich charge state of Au, is consistent with the order of the heats of adsorption for CO being monolayer Au on Mo > monolayer Au on titania > multilayer or bulk-like Au. 58 The electron-rich nature of Au nanoparticles is supported by theoretical calculations 30,45 and ancillary experimental data. 2,31,64,65 Electron transfer to Au nanoparticles has been probed by laser excitation of TiO 2 nanoparticles coated with Au nanoparticles, 66 by photoemission spectroscopy (PES), and by STM.…”

“…Because the density of corner, edge, or surface Au atoms relative to the number of total Au atoms in a particle increases with decreasing particle size, coordinatively unsaturated Au atoms at the corner, at the edge, and at the particle surface have been proposed to constitute the active sites. 19,30,34,45,50,53 Indeed, the binding of CO and O 2 are demonstratively higher at the corner or edge sites than on the terrace or on the smooth surface. 19,30,45 Moreover, DFT calculations show that oxygen and carbon monoxide can only adsorb on gold atoms with a coordination number less than 8 at a certain condition.…”

“…19,30,34,45,50,53 Indeed, the binding of CO and O 2 are demonstratively higher at the corner or edge sites than on the terrace or on the smooth surface. 19,30,45 Moreover, DFT calculations show that oxygen and carbon monoxide can only adsorb on gold atoms with a coordination number less than 8 at a certain condition. 53 This was confirmed by CO adsorption on Au/TiO 2 , Au/ZrO 2 , and Au/FeO using infrared spectroscopy.…”

“…34 the adsorption energy, particle shape, and the electronic structure of deposited Au nanoparticles and to influence their unique catalytic properties. 2,9,14,17,19,[25][26][27][28][29][30][31][32] Theoretical calculations have demonstrated that Au particles bind more strongly to a defect-rich surface compared with a defect-deficient surface and that significant charge transfer occurs from the titania support to the Au particles. 2,9,30,31 High-resolution STM combined with density functional theoretical (DFT) calculations 31 has confirmed that bridging oxygen vacancies are the active nucleation sites for Au particles on titania and that each vacancy site can bind approximately three Au atoms on average.…”

“…In particular, defects on the oxide support are thought to play a key role in anchoring the Au particles and in transferring electronic charge to Au, with these two effects in combination contributing to the special catalytic activity. 2,6,9,17,19,[27][28][29][30][31][32][33][34]56 The electronic state of Au nanoparticles can be probed using CO adsorption in combination with infrared spectroscopy. It has been shown that the ν CO mode shifts to lower frequency on electron-rich Au clusters and to higher frequency on electron-deficient clusters relative to bulk Au and that the extent of the shift can be correlated with the electronic charge on Au.…”