Involving Junction Perimeter Between Gold and the Metal-Oxide Supports

1 Mechanisms Involving Junction Perimeter Between Gold and the Metal-Oxide Supports 

The rate of CO oxidation over Au/Ti02, Au/Fe203 and Au/Co304 is almost independent of the concentration of CO and is slightly dependent ( 0.25 order) on the concentration of 02 down to a concentration of 0.1 vol.% [42], For unsupported 

Au powder with a mean particle diameter of 17 nm, the rate is almost independent of the concentration of 02 as well as CO [44]. This independence suggests that CO and 02 are adsorbed nearly to saturation on the catalyst surfaces and that the reaction of the two adsorbed species is the rate-determining step. 

2 Mechanisms Involving Specific Size or Thickness of Cold Clusters or Thin Layers 

Moreover, in the ordered Au monolayer and bilayer structures described above, the Ti4 + of the support titania is not accessible to the reactants, since each surface Ti site binds directly to a Au atom located at the topmost surface. The high catalytic activities for CO oxidation observed on ordered bilayer Au thus strongly suggest a Au-only CO oxidation pathway. The electronic nature of very small Au NPs and thin layers can be assumed to be significantly influenced by the nature and direct involvement of the Ti02 support and the Mo metal substrate, especially the availability of defect sites [26, 27, 88, 89]. 

---