Abstract
It is demonstrated that the support effects play a crucial role in the gold nanocatalysis. Two types of support are considered—the “inert” support of hexagonal boron nitride (h-BN) with the N and B vacancy defects and the “active” support of rutile TiO2(110). It is demonstrated that Au and Au2 can be trapped effectively by the vacancy defects in h-BN. In that case, the strong adsorption on the surface defects is accompanied by the charge transfer to/from the adsorbate. The excess of the positive or negative charge on the supported gold clusters can considerably promote their catalytic activity. Therefore gold clusters supported on the defected h-BN surface can not be considered as pseudo-free clusters. We also demonstrate that the rutile TiO2(110) support energetically promotes H2 dissociation on gold clusters. We show that the formation of the OH group near the supported gold cluster is an important condition for H2 dissociation. We demonstrate that the active sites towards H2 dissociation on the supported Aun are located at corners and edges of the gold cluster in the vicinity of the low coordinated oxygen atoms on TiO2(110). Thus catalytic activity of a gold nanoparticle supported on the rutile TiO2(110) surface is proportional to the length of the perimeter interface between the nanoparticle and the support.
Highlights
Since the pioneering work of Haruta on the oxidation of carbon monoxide on small gold nanoparticles supported by metal oxides [1], an extensive interest has been devoted to understanding the catalytic properties of gold
We show that the formation of the OH group near the supported gold cluster is an important condition for H2 dissociation and the conventional charge transfer mechanism does not play an important role for H2 dissociation
We start our study with investigation of the catalytic activity of small gold clusters supported on the defected hexagonal BN surface
Summary
Since the pioneering work of Haruta on the oxidation of carbon monoxide on small gold nanoparticles supported by metal oxides [1], an extensive interest has been devoted to understanding the catalytic properties of gold. In the case of the negatively charged gold nanoparticles, an extra electron from the gold readily transfers to the anti-bonding 2π ∗ orbital of the adsorbed O2 , which weakens the O–O bond and activates oxygen molecule for further catalytic reaction; see, e.g., References [10,11,29,30,31] and references therein. Two types of support will be considered—the hexagonal boron nitride (h-BN) with N and B vacancy defects and the rutile TiO2 (110) Using these two examples we show that the support effects on the catalytic activity of gold clusters can be rather diverse and can have different origins. It has been found experimentally that catalytic activity of gold nanoparticles supported on the rutile TiO2 (110) surface towards H2 dissociation depends on the number of gold atoms located at the perimeter nanoparticle-support interface, irrespective of the cluster size [38]. The considered phenomena can be important for understanding the mechanisms of the catalytic activity of the supported gold clusters in oxidation reactions by O2 and hydrogenation reactions by H2
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