Adsorption of molecular hydrogen and hydrogen sulfide on Au clusters

Abstract

The authors present theoretical results describing the adsorption of H2 and H2S molecules on small neutral and cationic gold clusters (Aun(0∕+), n=1–8) using density functional theory with the generalized gradient approximation. Lowest energy structures of the gold clusters along with their isomers are considered in the optimization process for molecular adsorption. The adsorption energies of H2S molecule on the cationic clusters are generally greater than those on the corresponding neutral clusters. These are also greater than the H2 adsorption energies on the corresponding cationic and neutral clusters. The adsorption energies for cationic clusters decrease with increasing cluster size. This fact is reflected in the elongations of the Au–S and Au–H bonds indicating weak adsorption as the cluster grows. In most cases, the geometry of the lowest energy gold cluster remains planar even after the adsorption. In addition, the adsorbed molecule gets adjusted such that its center of mass lies on the plane of the gold cluster. Study of the orbital charge density of the gold adsorbed H2S molecule reveals that conduction is possible through molecular orbitals other than the lowest unoccupied molecular orbital level. The dissociation of the cationic AunSH2+ cluster into AunS+ and H2 is preferred over the dissociation into AumSH2+ and Aun−m, where n=2–8 and m=1−(n−1). H2S adsorbed clusters with odd number of gold atoms are more stable than neighboring even n clusters.

Density Functional Study of Molecular Hydrogen Adsorption on Small Gold–Copper Binary Clusters

“…2 it can be observed that in all cases, the two H atoms prefer binding to the same metal atom and form H-H-M triangular geometry. Similar phenomenon has been also observed in H 2 molecular adsorption on small neutral and cationic Au n clusters [1][2][3]. In tetramers and pentamers the H atoms like to bond with the three-coordinated metal site, that is, H 2 prefers locating at the short diagonal of the rhombic tetramers and the upper bottom of the trapezoidal pentamers.…”

“…The phenomenon that H 2 dissociation was not observed experimentally is not due to the higher dissociation barrier and weak binding of H 2 . Kshirsagar et al investigated the adsorption of H 2 molecules on small neutral and cationic Au n clusters up to eight Au atoms [2]. They found that H 2 molecule weakly binds to the neutral Au n clusters as compared to the corresponding cationic Au n ?…”

“…mechanism and yield valuable evolution to bulk materials. The adsorption behaviors of H 2 on small metal clusters, such as Au, Pd, Cu, Ni and Pt, have been extensively investigated [1][2][3][4][5][6][7][8][9][10][11]. Chen et al performed a theoretical investigation on the adsorption and dissociation of H 2 onto small neutral and charged Au n (n = 1-6) clusters by using density functional theory (DFT) with the generalized gradient approximation [1].…”

A density functional theory study of the Au7Hn (n=1–10) clusters

“…In 1978, Hay et al [49] performed the ab initio studies on diatomic gold hydride using relativistic effective core potentials. Later, a number of experimental and theoretical studies have been reported about the interaction of the gold clusters with hydrogen [50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68]. In 2003, the photoelectron spectra of bare Au n À and Au n-1 H À clusters were presented by Buckart et al [68], and the spectra of Au n À and Au n-1 H À clusters showed almost identical features for n > 2 suggesting that hydrogen behaved as a protonated species by contributing one electron to the valence pool of the Au n À cluster.…”

The Interactions of Oxygen with Small Gold Clusters on Nitrogen-Doped Graphene

“…This has been investigated in some previous works for H 2 , NO, CO and H 2 O adsorption onto small Au clusters [41][42][43]. It can be seen from Figure 2 that for both end-on and bridge adsorption modes, the adsorption energies of O 2 on odd-numbered Au n clusters are larger than those on adjacent even-numbered ones.…”