Effects of Cluster Size on Platinum–Oxygen Bonds Formation in Small Platinum Clusters

Abstract

We present the results of density functional theory calculation in oxygen dissociative adsorption process on two types of isolated platinum (Pt) clusters: Pt4 and Pt10, by taking into account the effect of cluster reconstruction. The strength of Pt–Pt bonds in the clusters is mainly defined by d–d hybridization and interstitial bonding orbitals (IBO). Oxygen that adsorbed on the clusters is weakening the IBO and thus inducing geometry reconstruction as occurred in Pt10 cluster. However, cluster that could undergo structural deformation is found to promote oxygen dissociation with no energy barrier. The details show that maintaining well-balanced of attractive and repulsive (Hellmann–Feynman) forces between atoms is considered to be the main key to avoid any considerable rise of energy barrier. Furthermore, a modest energy barrier that gained in Pt4 cluster is presumed to be originate from inequality of intramolecular forces between atoms.

O2 Activation by Metal Surfaces: Implications for Bonding and Reactivity on Heterogeneous Catalysts

“…This barrier is lowered by substituting one Pt atom for Pd, which changes the structure from a flat disc to a trigonal bipyramid . For tetragonally shaped clusters, a lower barrier of 0.17 eV was calculated for Pt 4 , while O 2 dissociation on Pt 10 was barrierless . The reactivity of the latter was related to the flexibility of the cluster to adapt its geometry to the dissociating O 2 molecule.…”

“…Two different adsorption geometries of both O 2 and O on the Pt 4 and Pt 10 clusters were proposed based on DFT calculations. , In one study, the tetragonal-shaped cluster strongly deforms upon adsorption, even becoming flat for the Pt 4 cluster . In the other DFT study, the tetragonal shape remains largely intact …”

“…Small (2 n with n = 1–6) clusters of Pt and Pd are energetically inclined to dissociate O 2 based on DFT studies. , Compared to the extended Pt(111) surface, the binding of O is increased by 0.5 eV per O atom . The adsorption geometry is different from that on the extended surface, as the clusters prefer to bridge O between two Pt atoms.…”

Stability of Ni Clusters and the Adsorption of CH4: First-Principles Calculations

“…n n ads T 4 T T 4 (8) where E T [CH 4 ], E T [Ni n ], and E T [CH 4 −Ni n ] are the total energies of the bare CH 4 molecule, the relaxed free Ni n cluster in the gas phase, and the CH 4 −Ni n complex, respectively. From the curve of Δ 2 E in Figure 1, the local peaks are localized at n = 6, 10, 13, and possibly 15, indicating that these clusters are relatively more stable.…”

“…2,3 In catalytic reactions, they usually increase the selectivity and bond dissociation steps since they have more edge sites and lowcoordinated atoms. 4 Although in some reactions the presence of edge sites on the surface of nanoparticles can reduce the specific catalytic activity, 5 they are useful for different reactions, such as decomposition of hydrocarbons and alcohols, which can serve as important hydrogen sources. 6,7 Recently, much attention has been paid to the hydrogen production relating to the fuel cell technology.…”