Isomerization in Gold Clusters upon O₂ Adsorption

Abstract

A systematic investigation is performed on structural transformations in small neutral gold clusters (Au3–Au12) induced by O2 adsorption, with the use of the fully automated reaction path search techniques, i.e., anharmonic downward distortion following (ADDF) and artificial force induced reaction (AFIR) methods, implemented in the global reaction route mapping (GRRM) program. For each size of Au cluster, the most stable structure, low-energy isomers, and a network of isomerization pathways are determined. The located Au n –O2 adsorption forms can be classified into two groups: η1-Au n O2, where only one oxygen atom is adsorbed on Au n , and η2-Au n O2, where both oxygen atoms are adsorbed on Au n in a bridged manner. These two adsorption forms can be transformed to each other with a low barrier. The isomerization pathways of gold clusters upon O2 adsorption are compared with those obtained for the pure gold clusters without O2. It is demonstrated that O2 adsorption promotes structural transformations in gold clusters considerably by lowering the isomerization barriers. The presence of the unpaired electron is a necessary condition for O2 adsorption in the η1-Au n O2 form, as well as the subsequent cluster isomerization and the O–O bond activation. These conclusions are consistent with the recent experimental results by Fielicke et al.

Electronic Detection of Oxygen Adsorption and Size‐Specific Doping of Few‐Atom Gold Clusters on Graphene

“…Haruta et al first observed the remarkable catalytic activity of gold nanoparticles, notably toward oxidation reactions involving molecular oxygen. This has been extended to few‐atom Au m ( m ≲ 20) clusters in gas‐phase studies, illuminating their atom‐to‐atom size‐dependent affinity for oxygen adsorption and dissociation, relevant reaction pathways, and the dependence of the reactivity on the initial charge state of the cluster …”

“…For free (neutral) Au 3 clusters, one has observed two isomers which are close in energy (energy difference on the order of 20 meV) . One isomer has a triangular geometry, while the other isomer portrays a more linear shape.…”

“…The adsorbed Au 6 has a very similar planar structure as its neutral free cluster counterpart, with a minor change in bond lengths (≲0.01 Å) and bond angles (≲0.05°) (seeNote S3.5 in the Supporting Information). Au 6 adsorbs parallel to the graphene plane at an average distance of 3.29 Å (Figure b).…”

Global Optimization of Adsorbate Covered Supported Cluster Catalysts: The Case of Pt7H10CH3 on α‐Al2O3

“…Global optimization is the standard procedure for exploring the Potential Energy Surface (PES) and identifying the most stable structure of catalytic clusters . For gas phase and surface supported clusters, many different global optimization approaches have been extensively studied, including genetic algorithm, Basin Hopping (BH), and neural network fitting After the shape of catalytic clusters is identified by global optimization, the global minimum structure and possibly some other low‐energy isomers can be selected as reference states, for studying active sites for various reactants and corresponding reaction pathways . However, despite the relatively low computational cost, this scheme may not be reliable if the low‐energy bare‐cluster isomers do not appear to be the most active ones, or if a big shape change occurs upon the adsorption of reactants.…”

“…[11][12][13] For gas phase and surface supported clusters, many different global optimization approaches have been extensively studied, including genetic algorithm, [14,15] Basin Hopping (BH), [16,17] and neural network fitting [13,18,19] After the shape of catalytic clusters is identified by global optimization, the global minimum structure and possibly some other low-energy isomers can be selected as reference states, for studying active sites for various reactants and corresponding reaction pathways. [7,[20][21][22] However, despite the relatively low computational cost, this scheme may not be reliable if the low-energy bare-cluster isomers do not appear to be the most active ones, or if a big shape change occurs upon the adsorption of reactants. In particular, this will be the case when the catalytic cluster itself is highly fluxional, or if adsorbates affect the cluster shape.…”