Size Dependence of Low-Temperature Catalytic Activity of CO Oxidation Driven by Platinum Clusters Directly Bound to Silicon Substrate Surface

Abstract

Studied were cluster-size dependence of catalytic activity of CO oxidation driven by unisized platinum clusters, Pt N (N = 10, 30, and 60), directly bound to a silicon substrate surface. Temperature-programmed desorption measurements were repeated for a given Pt N /Si catalyst with systematic change of the reaction condition. The CO oxidation on the Pt N /Si catalyst is described in a manner similar to the bulk Pt(111) surface; the Langmuir−Hinshelwood mechanism by molecular oxygen activated by the catalyst at 120−140 K (α reaction) and the dissociatively adsorbed atomic oxygen in the temperature range of 130−350 K (β reaction). However, the Pt N /Si catalyst has the advantage of a lower-temperature activity compared with the bulk Pt(111) surface. Furthermore, the Pt 60 /Si catalyst has 1.5 times higher activity per Pt atom than Pt 30 /Si, while no catalytic activity for the Pt 10 /Si sample. These results are interpreted in relation to the geometric structure and the electron accumulation of the Pt clusters on the Si surface.

Activity of Pdn (n = 1–5) Clusters on Alumina Film on Ni3Al(111) for CO Oxidation: A Molecular Beam Study

“…It has been observed that single atoms (Pd1 or Pt1) are active or not in CO oxidation when they are supported on different substrates. In our experiment we use 12 C 16 O and 18 O2 and we detect 12 C 16 0 18 0 which proves that oxygen molecules have been dissociated before reaction with CO. This observation corresponds to the Langmuir-Hinshelwood (LH) mechanism which has been observed, using molecular beam methods, for Pd (or Pt) extended surfaces [35] and for Pd clusters [31].…”

“…Third, there is a lack of knowledge about the evolution of the catalytic activity as a function of the number of atoms forming the cluster. This last point can be in principle solved by experiments with size selected deposited clusters [12][13][14][15][16][17]. In 1999, U. Heiz and co-workers studied by temperature programmed reaction (TPR) the CO oxidation of Ptn (n= 5-20) clusters trapped on point defects of the surface on an MgO film [12].…”

The importance of particle-support interaction on particle size determination by gas chemisorption

“…To quantify the error associated to the assumption of spherical shapes in the metal nanoparticles in the estimated particle size, several 3D metal structures, widely observed experimentally for supported metal nanoparticles (Rossi et al 2004 ; Yasumatsu and Fukui 2015 ), have been considering: semi-octahedron, semi-truncated octahedron and truncated pyramid (frustum), as shown in Fig. 4 .…”

“…In addition to this, computational chemists, aided by advanced characterisation techniques, have also revealed the key relationship between catalytic activity and shape of the metal nanoparticles due to the selective exposure of different cluster facets and their effect on the adsorption strength of reactants. Indeed, several authors support the fact that the high activity of the metal nanoparticles is directly related to the high concentration of uncoordinated atoms in nano-sized particles (Lemire et al 2004 ), further promoted by specific 3D shapes (Molina et al 2011 ; Yasumatsu and Fukui 2015 ). For example, it is known that the optical response from metal nanoparticles and nanostructures is dominated by surface plasmon generation and is critically dependent on the local structure and geometry such as a range of polyicosahedral shapes or ellipsoids (Rossi et al 2004 ; Bosman et al 2007 ).…”

Single‐Site Heterogeneous Catalysts: From Synthesis to NMR Signal Enhancement

“…[114] One of the physicalmethods for the preparationo fd eposited clusters is mass-selective laser ablation. [115] Al arge number of novel clusters have been prepared by laser ablation:P t [116,117] and Pd [118,119] on MgO, TiO 2 , SiO 2 ,S i, graphite;c lusters of palladium oxides, [120] as well as clusters of Au on Al 2 O 3 , [121] MgO, [13] TiO 2 , [121,122] SiO 2 ; [123] Ag on Al 2 O 3 [124] and tested in CO oxidation, [13,95,116,117] cyclotrimerization of acetylene, [125] epoxidation of propene, [124] ethylene hydrogenation, [126] ando ther reactions.…”