DFT+U study on the oxygen adsorption and dissociation on CeO2-supported platinum cluster

Abstract

We investigated the reactivity of CeO 2 -supported Pt 4 cluster (denoted as Pt 4 /CeO 2 (111)) towards O 2 adsorption and dissociation as well as the geometry/electronic properties associated with such metal oxide supported cluster system using Density Functional Theory and on-site Coulomb interaction correction via the Hubbard-like term, U (DFT+U). It was found that Pt 4 binds strongly to CeO 2 (111) via Pt-O-Ce bonds which act as "anchors" between the surface and the cluster, confirming its non-sintering as found in experiments. The adsorption of the cluster involves net electron transfer to CeO 2 , however, charge redistribution also happens within the cluster (from Pt atom bonded to the surface to the Pt on top of the cluster). This charge couples to the top Pt leading to reduce its spin moment as compared to that of unsupported cluster. When O 2 adsorbs on Pt 4 /CeO 2 (111), while it prefers Pt vertex site near the CeO 2 surface, the O-O bond elongation is more profound at the Pt-Pt edges. The energy barrier for dissociating O 2 from this edge site precursor state is smallest. A correlation between the O-O bond length at the precursor state and the stability at the transition state is revealed. Finally, the barrier for dissociation in unsupported Pt 4 is lower, indicating suppression of the cluster's reactivity due to the support. We 2 attribute this to the hybridization of Pt-5d orbitals with O-2p orbitals in CeO 2 (111) leading to the broadening of Pt-5d states near the Fermi level.

Multiscale Approach to the Dissociative Adsorption of Oxygen on a Highly Dispersed Platinum Supported on γ-Al2O3

“…Systematic DFT calculations for clusters of variable size show that size effect is substantial for the adsorption of oxygen below about 150 atoms . Although many DFT studies deal with the adsorption of oxygen on flat or corrugated platinum surfaces, ,,,,− studies taking into account the support effect on the interaction of oxygen with platinum clusters are much scarcer, and generally concern very small clusters or single atoms and a single O 2 molecule. ,, A systematic investigation of the interaction of oxygen with sub-nanometric platinum cluster, typically Pt 13 , supported on γ-Al 2 O 3 , taking into account the effect of O coverage, function of the temperature and O 2 partial pressure, and possible reconstructions, is thus needed. The approach previously undertaken in the case of hydrogen interaction with Pt 13 /γ-Al 2 O 3 , revealing strong reconstructions of the metallic phase and modulation of the metal–support interaction upon variation of the H coverage, , is worth being extended to oxygen.…”

DFT studies of oxygen dissociation on the 116-atom platinum truncated octahedron particle

“…[13][14][15] Oxygen chemisorption studies have been performed on a number of extended Pt surfaces, [16][17][18] although there is also significant interest in the study of both free [19][20][21] and supported particle systems. 22,23 Nanoparticle models can offer a greater number of symmetry inequivalent sites at which to bind oxygen and in the size regime where ''each atom counts'', 24 properties are often dominated by quantum effects. For these structures, the under-coordinated surface atoms of the particles provide a diverse range of electronic environments at which to bind O.…”

Highly Selective pH-Dependent Ozonation of Cyclohexane over Mn/γ-Al2O3 Catalysts at Ambient Reaction Conditions

“…The rod-shaped particles also provide high surface area compared to spherical shaped particles [29]. In addition, the high catalytic performance of the Mn/γ-Al 2 O 3 catalysts can also be explained by aspects of the metal-support relationship of the metal-supported catalysts [28,[30][31][32]. That is, the γ-Al 2 O 3 support stabilises the MnO nanoparticles through electron transfer between the support and the metal.…”

“…In order to rationalize the effect of the reaction pH in both percentage conversion and selectivity, it is of crucial importance to consider the general free radical chain reaction mechanism proposed for the cyclohexane oxidation reactions [29,31,32]. The initial step of the oxidation involves C-H bond activation via hydrogen atom abstraction from cyclohexane to form cyclohexyl radical (i).…”