Effect of interparticle interaction on the low temperature oxidation of CO over size-selected Au nanocatalysts supported on ultrathin TiC films

Ono, Luis K.; Roldán-Cuenya, Beatriz

doi:10.1007/s10562-007-9027-7

Cited by 99 publications

(78 citation statements)

References 76 publications

(86 reference statements)

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“…Naturally oxidized Si(111) wafers and ultrathin Ti films (15 nm) electron-beam deposited on Si(111) have been used as NP supports. Further details on this preparation method can be found in refs [43][44][45][46][47][48]. A summary of the synthesis parameters used is given in Table 1.…”

Section: Methodsmentioning

confidence: 99%

“…In order to gain insight into these topics, we have used micelle encapsulation methods [43][44][45][46][47][48] to synthesize size-and shape-selected gold nanoclusters supported on thin SiO 2 and TiO 2 films. Morphological characterization was conducted by atomic force microscopy (AFM), and the decomposition of oxidized gold species, formed upon in situ O 2 plasma exposure, was investigated in UHV by XPS.…”

Section: Introductionmentioning

confidence: 99%

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Formation and Thermal Stability of Au₂O₃on Gold Nanoparticles: Size and Support Effects

2008

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Gold nanoparticles with two different size distributions (average sizes of ∼1.5 and ∼5 nm) have been synthesized by inverse micelle encapsulation and deposited on reducible (TiO 2 ) and nonreducible (SiO 2 ) supports. The thermal and chemical stability of oxidized gold species formed upon cluster exposure to atomic oxygen have been investigated in ultrahigh vacuum using a combination of temperature-, time-and CO dosingdependent X-ray photoelectron spectroscopy (XPS), as well as temperature-programmed desorption (TPD). Our work demonstrates that (a) low-temperature (150 K) exposure to atomic oxygen leads to the formation of surface as well as subsurface gold oxide on Au nanoparticles, (b) the presence of the reducible TiO 2 substrate leads to a lower gold oxide stability compared to that on SiO 2 , possibly because of a TiO 2 oxygen vacancy-mediated decomposition process, (c) heating to 550 K (Au/SiO 2 ) and 300 K (Au/TiO 2 ) leads to a near-complete reduction of small (∼1.5 nm) NPs while a partial reduction is observed for larger clusters (∼5 nm), and (d) the desorption temperature of O 2 from preoxidized Au clusters deposited on SiO 2 depends on the cluster size, with smaller clusters showing stronger O 2 binding.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Formation and Thermal Stability of Au₂O₃on Gold Nanoparticles: Size and Support Effects

2008

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“…19 In the latter, the attachment strength of CO on the TiC(001) surface or Au clusters is not very different, 20 but O 2 adsorption energy is higher on the Au-TiC(001) system. It should be borne in mind that titanium carbide is a cumbersome support to be used in applications due to the difficulty in obtaining nanoparticles under working conditions.…”

Section: -16mentioning

confidence: 97%

The bending machine: CO₂activation and hydrogenation on δ-MoC(001) and β-Mo₂C(001) surfaces

Posada‐Pérez

Viñes

Ramírez

et al. 2014

Phys. Chem. Chem. Phys.

182

284

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The adsorption and activation of a CO 2 molecule on cubic d-MoC(001) and orthorhombic b-Mo 2 C(001) surfaces have been investigated by means of periodic density functional theory based calculations using the Perdew-Burke-Ernzerhof exchange-correlation functional and explicitly accounting for (or neglecting) the dispersive force term description as proposed by Grimme. The DFT results indicate that an orthorhombic b-Mo 2 C(001) Mo-terminated polar surface provokes the spontaneous cleavage of a C-O bond in CO 2 and carbon monoxide formation, whereas on a b-Mo 2 C(001) C-terminated polar surface or on a d-MoC (001) nonpolar surface the CO 2 molecule is activated yet the C-O bond prevails. Experimental tests showed that Mo-terminated b-Mo 2 C(001) easily adsorbs and decomposes the CO 2 molecule. This surface is an active catalyst for the hydrogenation of CO 2 to methanol and methane. Although MoC does not dissociate C-O bonds on its own, it binds CO 2 better than transition metal surfaces and is an active and selective catalyst for the CO 2 + 3H 2 -CH 3 OH + H 2 O reaction. Our theoretical and experimental results illustrate the tremendous impact that the carbon/metal ratio has on the chemical and catalytic properties of molybdenum carbides. This ratio must be taken into consideration when designing catalysts for the activation and conversion of CO 2 .

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“…9. In general, the bond between Au and the TiC(001) surface exhibits very little ionic character, but there is a substantial polarization of electrons around Au [43] which enhances the chemical activity of this metal [10,44,45]. Figure 9 displays electron-polarization function (ELF) [28] plots for Au 2 and Au 4 on TiC(001).…”

Section: Hydrodesulfurization Of Thiophene On Au/tic and Au/moc Catalmentioning

confidence: 99%

Desulfurization Reactions on Surfaces of Metal Carbides: Photoemission and Density–Functional Studies

et al. 2010

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High-resolution photoemission and density functional (DF) calculations were used to study the interaction of atomic sulfur and S-containing molecules with metal carbides in which the carbon/metal ratio varies from 0.5 to 1 (M 2 C and MC, M = Ti, V or Mo). In these compounds, the C sites cannot be considered as simple spectators. They moderate the reactivity of the metal centers and provide bonding sites for adsorbates. For example, the adsorption of S on TiC(001) induces a large positive shift (1.0-1.3 eV) in the C 1s core level. DF calculations give a CTiTi hollow as the most stable site for the S adatoms. There is a correlation between the adsorption energy of S or thiophene and shifts in the centroid of the metal d band induced by metal-carbon bonding in the metal carbides. The M 2 C and MC carbides have difficulty obeying Sabatier's principle for being good HDS catalysts because some of them interact too strongly with the products (M 2 C stoichiometry) and the others have problems dissociating the reactants (MC stoichiometry). The addition of small Au nanoparticles is an efficient way for enhancing the HDS activity of MC catalysts. In spite of the very poor desulfurization performance of TiC and MoC, the Au/TiC and Au/MoC systems display an HDS activity comparable or higher than that of conventional Ni/MoS x catalysts. The Au nanoparticles probably increase the HDS activity of the metal carbides by enhancing the adsorption energy of thiophene and by helping in the dissociation of H 2 to produce the hydrogen necessary for the hydrogenolysis of C-S bonds and the removal of sulfur.

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Effect of interparticle interaction on the low temperature oxidation of CO over size-selected Au nanocatalysts supported on ultrathin TiC films

Cited by 99 publications

References 76 publications

Formation and Thermal Stability of Au₂O₃on Gold Nanoparticles: Size and Support Effects

Formation and Thermal Stability of Au₂O₃on Gold Nanoparticles: Size and Support Effects

The bending machine: CO₂activation and hydrogenation on δ-MoC(001) and β-Mo₂C(001) surfaces

Desulfurization Reactions on Surfaces of Metal Carbides: Photoemission and Density–Functional Studies

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Effect of interparticle interaction on the low temperature oxidation of CO over size-selected Au nanocatalysts supported on ultrathin TiC films

Cited by 99 publications

References 76 publications

Formation and Thermal Stability of Au2O3on Gold Nanoparticles: Size and Support Effects

Formation and Thermal Stability of Au2O3on Gold Nanoparticles: Size and Support Effects

The bending machine: CO2activation and hydrogenation on δ-MoC(001) and β-Mo2C(001) surfaces

Desulfurization Reactions on Surfaces of Metal Carbides: Photoemission and Density–Functional Studies

Contact Info

Product

Resources

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Formation and Thermal Stability of Au₂O₃on Gold Nanoparticles: Size and Support Effects

Formation and Thermal Stability of Au₂O₃on Gold Nanoparticles: Size and Support Effects

The bending machine: CO₂activation and hydrogenation on δ-MoC(001) and β-Mo₂C(001) surfaces