Density Functional Study of Hydrogen Binding on Gold and Silver−Gold Clusters

Abstract

A theoretical study was carried out on the binding of hydrogen on small bimetallic Ag(m)Au(n) (m + n < or = 5) and pure Au(n) (n < or = 5) clusters with neutral, negative, and positive charge state. It is found that the composition and charge state of clusters have strong influence on the most favorable binding site. The adiabatic ionization potentials, electron affinities, and hydrogen binding energies of cluster hydrides increase with the Au content increasing for the given cluster size. The cationic silver-gold cluster hydrides prefer ejection of Au-containing products whereas the anionic silver-gold cluster hydrides prefer ejection of Ag-containing products. The magnitude of metal-H frequency in combination with the metal-H bond length indicates that, with the same type of the binding site, the Au-H interaction is stronger than the Ag-H interaction.

Photoelectron imaging and theoretical calculations of gold–silver hydrides: comparing the characteristics of Au, Ag and H in small clusters

“…Comparison of the VDEs and ADEs obtained from both experiments and calculations is summarized in Table 1. Note that the theoretical VDEs calculated in our study are systematically lower than values from previous DFT results, 37 and our calculations are closer to the experimental results. …”

Catalyzed Surface-Aligned Reaction, H(ad) + H2(ad) = H2(g) + H(ad) on Coinage Metals

“…The explanation for this apparantly anomolous behaviour of gold is likely to be found in the fact that the chemical binding of H to Au is inadequately represented in the DFT approximation due to the need for relativistic corrections to account for the role of the d-orbitals in gold-hydride [34]. It is an open question whether in the case of Au an improved calculation of both E b and the heat of the H(ad) + H 2 (ad) exchange reaction would bring this coinage metal into accord with the BEP correlation described below.…”

Density functional study of molecular nitrogen adsorption on gold-copper and gold-silver binary clusters

“…The 6-311++G(d,p) basis set was used on N atoms. The accuracy of this methodology for bimetallic Au/Cu and Au/Ag clusters has been tested in our previous work [14,34]. All calculations were performed with (99,590) pruned grid (ultrafine grid as defined in Gaussian 09).…”

“…In recent years, bimetallic coinage metal clusters have attracted considerable attention both experimentally and theoretically primarily because they often exhibit distinct physical and chemical properties from the pure coinage clusters [2][3][4][5][6][7][8][9][10][11][12][13][14]. The bimetallic Au/Cu nanoparticles confined in SBA-15 have much better performance than monometallic particles in catalyzing CO oxidation even with the presence of excess H 2 [11].…”

“…They found that CO prefers binding to Cu and the adsorption energy generally decreases with increasing Cu content in the mixed clusters, which is highly related to the electron transfer between CO and the cluster. Our previous theoretical study showed that the ionization potentials (IP), electron affinities (EA), and hydrogen adsorption energies of bimetallic Ag/Au cluster hydrides increase as the Au content increases [14].…”