Unraveling molecular transformations on surfaces: a critical comparison of oxidation reactions on coinage metals

Li, Xiaoying; Madix, Robert J.; Friend, Cynthia M.

doi:10.1039/b800309m

Cited by 124 publications

(140 citation statements)

References 122 publications

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“…Of the allylic substrates investigated, only linalool, a tertiary allylic alcohol, was unreactive, reflecting the absence -carbon and higher activation barriers towards methyl C H bond activation [39]. It is immediately apparent that initial selox rates for the 0.74 wt% Pd/meso-Al 2 O 3 catalyst outperform those for the analogous amo -alumina support by at least a factor of two, and provides a 5 10 fold enhancement for crotyl and cinnamyl selox over mesoporous silica counterparts.…”

Section: Allylic Alcohol Seloxmentioning

confidence: 99%

Selective oxidation of allylic alcohols over highly ordered Pd/meso-Al2O3 catalysts

Parlett

Durndell

Wilson

et al. 2014

Catalysis Communications

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Highly ordered mesoporous alumina was prepared via evaporation induced self-assembly and was impregnated to afford a family of Pd/meso-Al 2 O 3 catalysts for the aerobic selective oxidation (selox) of allylic alcohols under mild reaction conditions. CO chemisorption and XPS identify the presence of highly dispersed (0.9 2 nm) nanoparticles comprising heavily oxidised PdO surfaces, evidencing a strong palladium-alumina interaction. Surface PdO is confirmed as the catalytically active phase responsible for allylic alcohol selox, with initial rates for Pd/meso-Al 2 O 3 far exceeding those achievable for palladium over either amorphous alumina or mesoporous silica supports. Pd/meso-Al 2 O 3 is exceptionally active for the atom efficient selox of diverse allylic alcohols, with activity inversely proportional to alcohol mass.

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Section: Allylic Alcohol Seloxmentioning

confidence: 99%

Selective oxidation of allylic alcohols over highly ordered Pd/meso-Al2O3 catalysts

Parlett

Durndell

Wilson

et al. 2014

Catalysis Communications

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“…A natural motivation for this study comes from the relevance of both Au and Ag for catalysis, e.g., Ag for ethylene epoxidation and Au for oxidation reactions (6,24). The two metals are similar.…”

Section: Au On Nial(110) and Comparison With Ag On Nial(110)mentioning

confidence: 99%

Self-assembly of metal nanostructures on binary alloy surfaces

Duguet

Han²,

Yuen

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Deposition of metals on binary alloy surfaces offers new possibilities for guiding the formation of functional metal nanostructures. This idea is explored with scanning tunneling microscopy studies and atomistic-level analysis and modeling of nonequilibrium island formation. For Au/NiAl(110), complex monolayer structures are found and compared with the simple fcc(110) bilayer structure recently observed for Ag/NiAl(110). We also consider a more complex codeposition system, ðNi þ AlÞ∕NiAlð110Þ, which offers the opportunity for fundamental studies of self-growth of alloys including deviations for equilibrium ordering. A general multisite lattice-gas model framework enables analysis of structure selection and morphological evolution in these systems.S elf-assembly involves the autonomous organization of components into structures (1). This process requires mobility of aggregating components, and usually occurs on smooth surfaces or in fluids. Some degree of relaxation in the aggregated state is typically also operative. Self-assembly can be manifested in either complex equilibrium structures, e.g., reflecting competing interactions, or in far-from-equilibrium growth structures (1). The latter can be very different and more diverse than the equilibrium forms (2). Significantly, self-assembly provides a practical strategy for creating ensembles of nanostructures with unique size and shape dependent properties, a central goal of nanotechnology.A broad range of systems self-assemble, spanning hard and soft matter, with a wide variety of interactions and component sizes. We consider the formation of metal nanostructures motivated by applications ranging from catalysis to plasmonics (3-5). Our specific focus is vapor deposition of metal atoms on single-crystal metal surfaces under the well controlled conditions of ultrahigh vacuum (UHV). This process leads to the self-assembly of metal nanostructures and growth of epitaxial metal films. Here, the nonaggregated components are rapidly diffusing adsorbed atoms (adatoms) which assemble into islands. Relaxation in the aggregated state can be achieved via diffusion of adatoms along island edges or via detachment-reattachment. Understanding these processes on the atomic scale facilitates guided formation of functional nanostructures with tailored morphologies and (for alloys) compositions. Ideally, control over formation allows tuning of desired properties, e.g., for heterogeneous catalysis (6).Despite the complexity of self-assembly processes, significant advances are being made in the development of predictive models even in soft material systems (7). Our focus on epitaxial growth on perfect single-crystal surfaces (hard materials) under UHV has a special advantage in facilitating extremely detailed and realistic atomistic-level modeling. Localization of adatoms to a periodic array of adsorption sites enables the use of lattice-gas (LG) models for which nonequilibrium evolution can be efficiently analyzed on the appropriate time-and length-scales via kinetic Monte Carlo (KMC)...

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“…It is therefore of fundamental and practical interest and importance to gain deeper insight into Au-based oxidation reactions, and to develop methods for improving their performance as catalysts for chemical transformations. Surface science studies have contributed greatly to our understanding of reaction mechanisms over Au, 32 but studies of oxygen activation on bench scale catalysts have been scarce. 33 Oxygen binding by Au single crystals and NPs is weak (less than 10 kJ/mol), 33 and direct measurements of the O 2 adsorption equilibrium constant have been unsuccessful.…”

mentioning

confidence: 99%

Enhanced Oxygen Activation over Supported Bimetallic Au−Ni Catalysts

et al. 2010

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New bimetallic Ni-Au supported nanoparticle catalysts were prepared by using dendrimer templated nanoparticles. Amine-terminated generation 5 polyamidoamine (PAMAM) dendrimers were anchored to a commercial silica with a siloxane linked anhydride. The dendrimer was then alkylated and used to template Ni-Au nanoparticles, which were subsequently extracted into organic solution as thiol monolayer protected clusters (MPCs). Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) indicated bimetallic nanoparticles of about 2 nm in size. Nanoparticles were deposited onto P-25 TiO 2 , and the capping thiol ligands were removed under flowing H 2 . DRIFTS infrared spectra of adsorbed CO showed only Au on the catalyst surface; no bands attributable to Ni or NiO were observed. Density functional theory (DFT) calculations showed that Au is substantially more stable than Ni on the surface of model slabs. DFT calculations also indicated that the incorporation of Ni into Au slabs results in stronger adsorption of O and CO on Au surfaces. Catalysts were evaluated with low-temperature CO oxidation. Kinetics studies indicated a substantial modification of Au catalysis through Ni incorporation. Apparent activation energies decreased by more than 50% and O 2 reaction orders increased from 0.2 to 0.9. These results are placed in the context of the available literature regarding support effects for Au catalysts. The observed changes to Au chemistry in the current work are substantially larger than previous reports have attributed to support effects. A Michaelis-Menten (enzyme) treatment of the kinetics data indicated that the O 2 reactivity constant increased by a factor of 40 for catalysts with high Ni content. This was in good qualitative agreement with the DFT calculations. At the same time, the introduction of Ni reduced the relative number of catalytically active sites.

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Unraveling molecular transformations on surfaces: a critical comparison of oxidation reactions on coinage metals

Cited by 124 publications

References 122 publications

Selective oxidation of allylic alcohols over highly ordered Pd/meso-Al2O3 catalysts

Selective oxidation of allylic alcohols over highly ordered Pd/meso-Al2O3 catalysts

Self-assembly of metal nanostructures on binary alloy surfaces

Enhanced Oxygen Activation over Supported Bimetallic Au−Ni Catalysts

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