Size Effects of Atomically Precise Gold Nanoclusters in Catalysis

Abstract

The emergence of ligand-protected, atomically precise gold nanoclusters (NCs) in recent years has attracted broad interest in catalysis due to their well-defined atomic structures and intriguing properties. Especially, the precise formulas of NCs provide an opportunity to study the size effects at the atomic level without complications by the polydispersity in conventional nanoparticles that obscures the relationship between the size/structure and properties. Herein, we summarize the catalytic size effects of atomically precise, thioate-protected gold NCs in the range of tens to hundreds of metal atoms. The catalytic reactions include electrochemical catalysis, photocatalysis, and thermocatalysis. With the precise sizes and structures, the fundamentals underlying the size effects are analyzed, such as the surface area, electronic properties, and active sites. In the catalytic reactions, one or more factors may exert catalytic effects simultaneously, hence leading to different catalytic-activity trends with the size change of NCs. The summary of literature work disentangles the underlying fundamental mechanisms and provides insights into the size effects. Future studies will lead to further understanding of the size effects and shed light on the catalytic active sites and ultimately promote catalyst design at the atomic level.

Structure control and evolution of atomically precise gold clusters as heterogeneous precatalysts

“…), and photochemical reactions (CO 2 reduction, 57,58 dye degradation, 59 etc .). The catalytic activity of medium-sized gold nanoclusters is not solely determined by the size (this has been summarized in recent reviews 60,61 ), but is also related to the surface geometry, electronic properties, and ligand properties of the nanoclusters and cluster–support interaction. Ultimately, the structural evolution of the supported cluster during catalyst pretreatment and reaction creates the actual active sites.…”

Atomically precise gold nanoclusters for CO oxidation: balancing activity and stability by ligand shedding

“…As shown in table 1, with an increasing number of shedding ligands, the binding strength of O 2 species on the exposed Au atoms of ligand Au NCs are weakened, corresponding to the adsorption energies of −1.14 to −0.56 eV, 0.80 eV to −0. 25 [44][45][46]49]. This is due to the mutual repulsion forces undergone by the filled d orbital electrons in the Au atoms with the antibonding states and the adsorbed states [49,50].…”

“…The rational synthesis of atomically precise Au NCs has paved the way for gaining fundamental insight into the intrinsic mechanism and establishing the structure-property-application relationship of Au NCs. In recent decades, both experimental and theoretical studies have demonstrated that these NCs have optimal catalytic properties, such as selective oxidation [12][13][14], selective hydrogenation [15][16][17][18], carbon-carbon coupling [19][20][21], photocatalytic [22], photoelectronic and photothermal reaction [23][24][25].…”

“…The ligand shell surrounding the metal core has been shown to regulate the size, stability and reactivity of these clusters, making them highly tunable for basic energy catalysis [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. For instance, phosphine-coordinated Au 11 NCs with partial ligand removal exhibit high chemical activity for roomtemperature CO oxidation involving a kinetic barrier of 0.7 eV.…”

The role of metal accessibility on carbon dioxide electroreduction in atomically precise nanoclusters

“…Changes to the arrangement of surface ligands and metal atoms-as well as the electronic structure of the NC-may also affect the outcome of catalytic reactions, further convoluting structure-property relationships. 32 Indeed, differing trends have been reported for how NC size affects CO 2 RR activity. For example, in the series Au 25 (SR) 18 , Au 38 (SR) 24 , and Au 144 (SR) 60 (SR = SC 2 H 4 Ph), CO 2 RR activity increases with increasing NC size, 33 while other studies have found that the FE CO of Au-SR NCs is not directly affected by NC size.…”