(139e) Investigation of the Catalytically Active Site in Oxidation Catalysis by Gold: Insights From First Principles

A Fundamental understanding of the physical mechanisms that govern the catalytic activity and long term stability of oxide supported gold (Au) catalysts is essential for the Au catalyst design and optimization. Two critical questions addressed in our study are: (1) What is the catalytically active form of Au (cationic, metallic, or anionic Au)? and (2) What is the active site or sites responsible for the unprecedented activity of oxide supported nanostructured Au? To shed light on these questions we have utilized quantum chemical and ab initio thermodynamic calculations.

By scrutinizing many different Au/Oxide model systems we found that the Au?Oxide interface/perimeter plays a critical role in activating Au sites within an Au nano-structure. More specifically, we found that strong interactions between the Au nano-structure and oxide surface defects, either oxygen vacancies or extra oxygen atoms at the Au?Oxide interface, enhances the chemical activity of the Au nanostructure. We also found in the ab initio thermodynamics studies that the concentration of oxide surface defects depends on the external operating conditions.

Our studies also showed that the external operating conditions also govern the electronic fingerprint of Au and the electronic nature of the catalytically active sites. We will also discuss the impact of the catalyst synthesis and pretreatment on the electronic structure and the activity of Au/oxide catalysts.