CO Oxidation Mechanism on CeO<sub>2</sub>-Supported Au Nanoparticles

Kim, Hyun You; Lee, Hyuck Mo; Henkelman, Graeme

doi:10.1021/ja207510v

Cited by 512 publications

(588 citation statements)

References 82 publications

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“…Second, the HOMO of the Au SAC is spinminority dominated, and the spin-majority orbitals are totally Having clearly illustrated the critical step for O 2 activation by the Au cation on the Ni-doped TiO 2 (110) complex, we now investigate the kinetic processes of CO oxidation using the optimized NEB method. 46 Note that three CO oxidation mechanisms proposed by recent theoretical investigations 47,48 have been examined in the present study. We conrmed that the CO oxidation surprisingly prefers a quasi-Langmuir-Hinshelwood (L-H) process in this case, namely, CO can adsorb relatively weakly on the single Au atom close to the adsorbed O 2 molecule and the co-adsorbed molecules undergo a bimolecular reaction through the formation of a CO 2 precursor, which is subsequently released upon further activation, and the optimized substrate structure upon CO 2 desorption is shown as the initial state (IS) conguration in Fig.…”

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confidence: 89%

An oxidized magnetic Au single atom on doped TiO₂(110) becomes a high performance CO oxidation catalyst due to the charge effect

et al. 2017

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Catalysis using gold nanoparticles supported on oxides has been under extensive investigation for many important application processes. However, how to tune the charge state of a given Au species to perform a specific chemical reaction, e.g. CO oxidation, remains elusive. Here, using first-principles calculations, we show clearly that an intrinsically inert Au anion deposited on oxygen-deficient TiO 2 (110) (Au@TiO 2 (110)) can be tuned and optimized into a highly effective single atom catalyst (SAC), due to the depletion of the d-orbital by substrate doping. Particularly, Ni-and Cu-doped Au@TiO 2 complexes undergo a reconstruction driven by one of the two dissociated O atoms upon CO oxidation. The remaining O atom heals the surface oxygen vacancy and results in a stable bow-shaped surface "O-Au-O" species; thereby the highly oxidized Au single atom now exhibits magnetism and dramatically enhanced activity and stability for O 2 activation and CO oxidation, due to the emergence of high density of states near the Fermi level. Based on further extensive calculations, we establish the "charge selection rule" for O 2 activation and CO oxidation on Au: the positively charged Au SAC is more active than its negatively charged counterpart for O 2 activation, and the more positively charged the Au, the more active it is.

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confidence: 89%

An oxidized magnetic Au single atom on doped TiO₂(110) becomes a high performance CO oxidation catalyst due to the charge effect

et al. 2017

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“…In the case of supported, bare gold particles (as opposed to our ligands-on Au particles), Guzman et al observed reactive oxygen in the form of surface superoxide and peroxide species in CO oxidation. 41 Very recently, Kim et al 42 discussed three CO oxidation mechanisms on CeO 2 -supported Au nanoparticles on the basis of DFT calculations, including (1) CO oxidation by coadsorbed O 2 , (2) by lattice oxygen in CeO 2 , and (3) by O 2 bound to a AuÀCe 3þ anchoring site. While all these works refer to bare Au particles, in our case, the Au 25 particles are capped by thiolate ligands and there are possibly some major differences between the two systems.…”

Section: Articlementioning

confidence: 99%

CO Oxidation Catalyzed by Oxide-Supported Au₂₅(SR)₁₈ Nanoclusters and Identification of Perimeter Sites as Active Centers

et al. 2012

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In this work, we explore the catalytic application of atomically monodisperse, thiolate-protected Au 25 (SR) 18 (where R = CH 2 CH 2 Ph) nanoclusters supported on oxides for CO oxidation.The solution phase nanoclusters were directly deposited onto various oxide supports (including TiO 2 , CeO 2 , and Fe 2 O 3 ), and the as-prepared catalysts were evaluated for the CO oxidation reaction in a fixed bed reactor. The supports exhibited a strong effect, and the Au 25 (SR) 18 /CeO 2 catalyst was found to be much more active than the others. Interestingly, O 2 pretreatment of the catalyst at 150 °C for 1.5 h significantly enhanced the catalytic activity. Since this pretreatment temperature is well below the thiolate desorption temperature (∼200 °C), the thiolate ligands should remain on the Au 25 cluster surface, indicating that the CO oxidation reaction is catalyzed by intact Au 25 (SR) 18 /CeO 2 . We further found that increasing the O 2 pretreatment temperature to 250 °C (above the thiolate desorption temperature) did not lead to any further increase in activity at all reaction temperatures from room temperature to 100 °C. These results are in striking contrast with the common thought that surface thiolates must be removed ; as is often done in the literature work ; before the catalyst can exert high catalytic activity. The 150 °C O 2pretreated Au 25 (SR) 18 /CeO 2 catalyst offers ∼94% CO conversion at 80 °C and ∼100% conversion at 100 °C. The effect of water vapor on the catalytic performance is also investigated. Our results imply that the perimeter sites of the interface of Au 25 (SR) 18 /CeO 2 should be the active centers.The intact structure of the Au 25 (SR) 18 catalyst in the CO oxidation process allows one to gain mechanistic insight into the catalytic reaction.

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“…It has been shown that Au 7 is the smallest Au cluster on rutile TiO 2 (110) with a measurable reaction rate for CO combustion [19]. The Au 11 model, although being a simplification of the nanometersized clusters on TiO 2 (110), appropriately mimics the active sites located at the nanogold/oxide interface where the oxidation process takes place [6,20]. The binding of the Au 11 cluster on the reduced TiO 2 (110) support entails a strong charge rearrangement at the metal/oxide contact (see Supporting Figure 1), the adsorption energy being −2.19 eV.…”

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On the Impact of Solvation on a Au/TiO₂Nanocatalyst in Contact with Water

Camellone

Marx

2013

J. Phys. Chem. Lett.

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Water, the ubiquitous solvent, is also prominent in forming liquid-solid interfaces with catalytically active surfaces, in particular with promoted oxides. We study the complex interface of a gold nanocatalyst, pinned by an F-center on titania support, and water. The ab initio simulations uncover the microscopic details of solvent-induced charge rearrangements at the metal particle. Water is found to stabilize charge states differently from the gas phase as a result of structure-specific charge transfer from/to the solvent, thus altering surface reactivity. The metal cluster is shown to feature both "cationic" and "anionic" solvation, depending on fluctuation and polarization effects in the liquid, which creates novel active sites. These observations open up an avenue toward "solvent engineering" in liquid-phase heterogeneous catalysis.Highly dispersed gold nanoparticles supported on oxides have been shown to catalyze a number of important reactions, including low-temperature CO oxidation and the water gas shift reaction [1,2]. Reducible oxides, in particular titania (TiO 2 ), are ideal catalytic supports [3]. The size of the gold particles substantially affects the catalytic activity, suggesting the key importance of metal/support interactions on a nanometer scale [4]. Reactions, and in particular CO oxidation, are believed to occur at specific active Au sites at the Au/TiO 2 interface [5][6][7][8]. Although much is known regarding Au/TiO 2 catalytic activity in the presence of a gas phase, the complexity increases steeply when solvent is included.Liquid-solid interfaces as such are relevant to many industrial applications of great significance, such as (photo-)catalysis, solar cells, gas sensors, or biocompatible devices. In heterogeneous catalysis, it has been shown that the presence of water increases the observed rate of CO oxidation [9,10]. The degree of rate enhancement depends on the type of support used. In particular for the case of Au/TiO 2 catalysts it has been shown that their activity at about 3000 ppm H 2 O is so high that full conversion of CO is reached [10]. Thus, the Au/TiO 2 surface displays a pronounced catalytic activity toward the water-gas-shift (WGS) reaction. This fundamental reaction represents a key reaction to produce extra H 2 fuel from steam reforming, which is reversible and exothermic, according to the following reaction: CO + H 2 O ⇌ CO 2 + H 2 . The so-called carboxyl and redox mechanisms have been proposed for the WGS reaction on metal/oxide surfaces; in the former mechanism the CO species reacts with terminal hydroxyl groups, whereas in the latter CO reacts with an O atom from OH dissociation or from the oxide support. In both mechanism proposed the starting point is a H 2 O molecule that is initially adsorbed on the metallic cluster with its oxygen atom being attached to a metal atom.Moreover, even large (as opposed to nanoscale) gold particles, which are usually catalytically inert, show considerable oxidation activity at aqueous conditions [11,12]. Because of its high diel...

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CO Oxidation Mechanism on CeO₂-Supported Au Nanoparticles

Cited by 512 publications

References 82 publications

An oxidized magnetic Au single atom on doped TiO₂(110) becomes a high performance CO oxidation catalyst due to the charge effect

An oxidized magnetic Au single atom on doped TiO₂(110) becomes a high performance CO oxidation catalyst due to the charge effect

CO Oxidation Catalyzed by Oxide-Supported Au₂₅(SR)₁₈ Nanoclusters and Identification of Perimeter Sites as Active Centers

On the Impact of Solvation on a Au/TiO₂Nanocatalyst in Contact with Water

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CO Oxidation Mechanism on CeO2-Supported Au Nanoparticles

Cited by 512 publications

References 82 publications

An oxidized magnetic Au single atom on doped TiO2(110) becomes a high performance CO oxidation catalyst due to the charge effect

An oxidized magnetic Au single atom on doped TiO2(110) becomes a high performance CO oxidation catalyst due to the charge effect

CO Oxidation Catalyzed by Oxide-Supported Au25(SR)18 Nanoclusters and Identification of Perimeter Sites as Active Centers

On the Impact of Solvation on a Au/TiO2Nanocatalyst in Contact with Water

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CO Oxidation Mechanism on CeO₂-Supported Au Nanoparticles

An oxidized magnetic Au single atom on doped TiO₂(110) becomes a high performance CO oxidation catalyst due to the charge effect

An oxidized magnetic Au single atom on doped TiO₂(110) becomes a high performance CO oxidation catalyst due to the charge effect

CO Oxidation Catalyzed by Oxide-Supported Au₂₅(SR)₁₈ Nanoclusters and Identification of Perimeter Sites as Active Centers

On the Impact of Solvation on a Au/TiO₂Nanocatalyst in Contact with Water