Bulk Au is the most inert metal of the periodic table. However, when in contact with an oxide support as a nano-particle it can exhibit unprecedented catalytic activity at low temperatures (300 K). It has been well documented that the activity of these types of catalysts is a strong function of the type of support material used to disperse the metal.
I will discuss our recent studies focused on determining the underlying mechanisms by which oxide supports affect the chemical activity of small Au nanostructures and general insights into how the inert metal can be catalytically active at low temperatures. I will also discuss how this molecular information was used to identify optimal preparation strategies allowing us to synthesize highly active Au catalysts.
We used a combination of experimental and first principles theoretical techniques to investigate the Au/oxide system. From our ab initio calculations, we found that: i) the oxide surface can directly affect the chemistry of Au, only when oxide surface defects are present (reduced or over oxidized support), and ii) there are highly active sites at the perimeter of Au particles in close proximity to or in direct contact with the oxide support. We found that the interactions (electrostatic/electronic) at or near the Au/oxide interface dictated the stability and activation of adsorbates, the stability of non-metallic Au species, the extent of halide poisoning, and the thermodynamic driving force for oxygen reduction at active sites.
These fundamental insights were used to develop a catalyst preparation procedure that allowed us to manipulate the concentration of the above-mentioned, active, interface sites and to test some of the proposed hypotheses. The catalysts were characterized by EXAFS, XANES, STEM, XPS, and UV-Vis spectroscopies These experimental results were in direct agreement with our theoretical predictions.