An Atomic-Level Strategy for Unraveling Gold Nanocatalysis from the Perspective of Au-n(SR)(m) Nanoclusters

An atomic-level strategy is devised to gain insight into the origin of nanogold catalysis by using atomically monodisperse Au-n(SR)(m) nanoclusters as well-defined catalysts for styrene oxidation. The Au-n(SR)(m) nanoclusters are emerging as a new class of gold nanocatalyst to overcome the polydispersity of conventional nanoparticle catalysts. The unique atom-packing structure and electronic properties of Au-n(SR)(m) nanoclusters (<2 nm) are rationalized to be responsible for their extraordinary catalytic activity observed in styrene oxidation. An interesting finding is that quantum size effects of Au-n(SR)(m) nanoclusters, rather than the higher specific surface area, play a major role in gold-catalyzed selective oxidation of styrene. For example, Au-25(SR)(18) nanoclusters (approximate to 1 nm) are found to be particularly efficient in activating O-2, which is a key step in styrene oxidation, and hence, the ultrasmall Au-25 catalyst exhibits higher activity than do larger sizes. This atomic-level strategy has allowed us to obtain an important insight into some fundamental aspects of nanogold catalysis in styrene oxidation. The ultrasmall yet robust Au-n(SR)(m) nanoclusters are particularly promising for studying the mechanistic aspects of nanogold catalysis and for future design of better catalysts with high activity and selectivity for certain chemical processes.