Electron-Rich Gold Clusters Stabilized by Poly(vinylpyridines) as Robust and Active Oxidation Catalysts

Abstract

In this report, we introduced poly­(n-vinylpyridine) (PnVP, n = 2, 4) as an electron-donating stabilizer for small (<2 nm) Au clusters and elucidated how coordinating pyridines affect the physical, optical, chemical, and catalytic properties of Au clusters. Spectroscopic measurements and theoretical calculation suggested the high electron-donating ability of PnVP. PnVP-stabilized Au clusters improved robustness in aerobic oxidation of alcohols compared to poly­(N-vinyl-2-pyrrolidone)-stabilized ones, while retaining catalytic activities.

In Situ Electrochemical XPS Monitoring of the Formation of Anionic Gold Species by Cathodic Corrosion of a Gold Electrode in an Ionic Liquid

“…The above-mentioned results show that the reduction of Au to Au – in a NH 3 electrolyte occurs at −2.4 V versus Ag/AgNO 3 . It was reported that anionic Au clusters stabilized by poly­( N -vinyl-2-pyrrolidone) (PVP) polymers showed an Au 4f 7/2 BE of between 83.0 and 82.0 eV. , Considering we have applied a voltage of −3.0 V, the Au 4f 7/2 BE at ∼85.0 eV, as shown in Figure a, can be reasonably attributed to anionic Au species, which are formed during the cathodic corrosion of gold. The small differences in the BE shifts of the anionic Au – between the Au-sputtered Cu mesh and Au wire electrode may attribute to the formation of different Au species or anionic Au clusters.…”

New Magic Au24 Cluster Stabilized by PVP: Selective Formation, Atomic Structure, and Oxidation Catalysis

“…B3LYP was used as a functional. , A double-ζ basis set with scalar relativistic effective core potential (ECP), LANL2DZ, was applied for Au and the 6-31+G­(d) basis set was used for C, O, and Cl. Structures of Au 24 were obtained by reoptimization of those reported previously. , PVP was not included in the calculations since the impact on the atomic structure of Au clusters is negligibly small . Neutral clusters (Au 24 , Au 24 (CO) 1 , and Au 24 Cl 4 ) were optimized with the singlet spin state, whereas the doublet spin state was applied for the anionic cluster, Au 24 (CO) 1 – .…”

“…70,71 PVP was not included in the calculations since the impact on the atomic structure of Au clusters is negligibly small. 72 Neutral clusters (Au 24 , Au 24 (CO) 1 , and Au 24 Cl 4 ) were optimized with the singlet spin state, whereas the doublet spin state was applied for the anionic cluster, Au 24 (CO) 1 − . The vibrational frequencies were computed for the optimized structures to ensure that they corresponded to the local minima of the potential energy surface.…”

Catalytic Activity of Gold Clusters Supported on the h-BN/Au(111) Surface for the Hydrogen Evolution Reaction

“…Small metal clusters and nanoparticles play an extraordinary role in catalysis due to the emergence of unique physical and chemical properties at the nanoscale. − Small nanoparticles are especially attractive in catalysis because of the appearance of a large fraction of the low coordinated and active surface sites accessible to reactants and leading to the high efficiency in metal utilization. , In this regime the properties of metal clusters are often nonscalable and strongly depend on the cluster size, structure, morphology, presence of dopants, charge state, and support effects which make clusters an ideal material for a rational design of catalysts with the tailored properties. , Gold is perhaps one of the most fascinating examples in nanocatalysis, demonstrating a transition from the catalytically inert bulk form to the highly active clusters and nanoparticles. ,, It has been demonstrated that small gold clusters show extraordinary size-dependent catalytic activity and selectivity, especially for the oxidation reactions involving molecular oxygen, because of the ability to activate the O–O bond (see, e.g., refs − and references therein) as well as reactions involving H bond activation and H 2 dissociation (see, e.g., refs − and references therein). Currently, a large variety of catalytic reactions on gold clusters have been studied both theoretically and experimentally, and the number of works related to the gold nanocatalysis is growing exponentially. , Thus, it has recently been demonstrated that gold nanoparticles can exhibit catalytic activity for the key reactions of the sustainable energy cycle, such as the hydrogen evolution reaction (HER) − and the oxygen reduction reaction. ,,− These findings suggest that gold clusters can be very attractive for energy-related applications and in particular for the hydrogen-based technologies.…”