Heats of Adsorption of Linear CO Species Adsorbed on the Au° and Ti+δ Sites of a 1% Au/TiO2 Catalyst Using in Situ FTIR Spectroscopy under Adsorption Equilibrium

Derrouiche, Salim; Gravejat, P.; Bianchi, Daniel

doi:10.1021/ja0470719

Cited by 88 publications

(138 citation statements)

References 49 publications

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“…Our approaches can be compared with the more complicated Temkin isotherm analysis utilized by Bianchi 26 and Behm. 21 In that model, the binding energy (or heat of adsorption) is assumed to vary linearly from a low coverage (E 0 at θ ) 0) to a high coverage value (E 1 at θ ) 1).…”

Section: Discussionmentioning

confidence: 99%

Adsorption of CO on Supported Gold Nanoparticle Catalysts: A Comparative Study

2009

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The adsorption of CO on three different gold nanoparticle catalysts supported on high surface area TiO 2 was studied using infrared transmission spectroscopy at room temperature and CO pressures typically used in CO oxidation reactions. The three, real-world catalysts were Au catalysts synthesized in our laboratory from thiol monolayer protected clusters (MPCs) and two commercial catalysts from the World Gold Council (WGC and AuTEK). Within experimental reproducibility, the adsorption data for the three catalysts are indistinguishable. While showing approximately Langmuir behavior, the adsorption data also show coverage dependence, as others have observed for many catalyst systems. Two approaches were used to fit the data, a two-site model and a variable binding constant model. The two-site Langmuir model yielded strong (36%) and weak (64%) binding constants of 2740 and 146 atm -1 , respectively. Alternatively, using a sliding-tangent Langmuir fit gave a variable binding constant of 2670-120 atm -1 at room temperature for coverage θ ) 0-0.8. The heat of adsorption was then extracted from the binding constants using a literature value for -T∆S. These values were determined as ∆H ) -64 and -56 kJ/mol for strong and weak binding according to the two-site model and ∆H ) -63 to -56 kJ/mol for coverage θ ) 0-0.8 for the variable binding constant model. These values agree well with literature values obtained (i) using supported catalysts under higher pressures and (ii) using model catalysts under higher pressures and ultrahigh vacuum conditions.

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Section: Discussionmentioning

confidence: 99%

Adsorption of CO on Supported Gold Nanoparticle Catalysts: A Comparative Study

2009

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“…Infrared spectroscopy (AEIR: absorption equilibrium infrared) was used to quantify the CO adsorption coverage. Two isobars at P = 1 and 10 kPa over a temperature range of T ≈ 300−400 K were reported in Figure 4 of ref 22.…”

Section: ■ Application Of the Temkin Adsorbatementioning

confidence: 99%

CO Adsorption on Supported Gold Nanoparticle Catalysts: Application of the Temkin Model

et al. 2012

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The adsorption of CO on the supported gold nanoparticle catalysts Au/TiO 2 , Au/Fe 2 O 3 , and Au/ZrO 2 was examined using infrared transmission spectroscopy to quantify the isobaric CO coverage as a function of temperature. The Temkin adsorbate interaction model was then applied to account for the adsorption behavior. To test the general applicability of the Temkin model, this treatment was also applied to three data sets from the literature. This included another real-world catalyst and two model catalysts. All data sets were accurately represented by the Temkin adsorbate interaction model. The resulting thermodynamic metrics are consistent with previous determinations and reflect a particle size-dependence. In particular, the intrinsic adsorption enthalpy at zero CO coverage varies almost linearly with Au particle size, and this trend appears to be correlated with the abundance of low-coordinate Au sites (cf., CN = 6 and 7 for corners and edges, respectively). For very small particles with mostly CN = 6 corner sites, the enthalpy reflects strong binding (cf., −ΔH 0 ≈ 78 kJ/mol), while for large particles with mostly CN = 7 edge sites, the enthalpy reflects weaker binding (cf., −ΔH 0 ≈ 63 kJ/mol). The results also suggest that these sites are coupled. This study demonstrates that the Temkin adsorbate interaction model accurately represents adsorption data, yields meaningful metrics that are useful for characterizing nanoparticle catalysts, and should be applicable to other adsorption data sets.

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“…[28,29] For the influence of neighboring Au atoms, the CO adsorption will be strengthened when some neighboring Au atoms increase the bonding with r-orbitals (d z2 orbitals) of the Au atom connected to CO. This is because the Au-Au r-bonding should decrease N r of Au-CO, via the electron transfer from the Au-C-O bonding to the Au-Au bonding as shown in Figure 1.…”

Section: Journal Of Computational Chemistrymentioning

confidence: 99%

“…The doping metal atom in gold cluster, such as Ag, Cu, and Y, could act as electron donor, because their work functions (4.26, 4.65, and 3.1 eV [36] for Ag, Cu, and Y, respectively) are lower than gold (5.1 eV). [36] As CO is normally adsorbed on the top site, [28,29] it is predicted by Hü ckel theory that these doping metals (Ag, Cu, and Y) will weaken the CO adsorption. It have been proven that the CO adsorption on doped gold cluster by Ag, Cu, and Y actually is weaker than that on pure gold cluster by the experimental [37,38] or theoretical [39][40][41] studies.…”

Section: Co-adsorption or Doping With Electron Donor Or Acceptormentioning

confidence: 99%

A theoretical study of CO adsorption on gold by Hückel theory and density functional theory calculations

et al. 2011

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It is crucial to understand the nature of CO adsorption on gold so as to elucidate the mechanism of low-temperature CO oxidation on nanogold catalysts. We performed theoretical analysis of CO adsorption on gold by using Hückel theory and density functional theory (DFT) calculations. Hückel theory indicates that CO adsorption on gold is dominated by the electron distribution at the Au atom, which is greatly affected by neighboring Au atoms, coadsorbed or doping species. The increase of σ-bonding electrons should weaken the CO adsorption, while the increase of π-electrons should strengthen the adsorption. DFT calculations proved this prediction quantitatively for various systems, including CO adsorption on a Au(100)-hex surface with locally varying subsurface configurations and CO coadsorption with acceptor or donor species.

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Heats of Adsorption of Linear CO Species Adsorbed on the Au° and Ti⁺^δ Sites of a 1% Au/TiO₂ Catalyst Using in Situ FTIR Spectroscopy under Adsorption Equilibrium

Cited by 88 publications

References 49 publications

Adsorption of CO on Supported Gold Nanoparticle Catalysts: A Comparative Study

Adsorption of CO on Supported Gold Nanoparticle Catalysts: A Comparative Study

CO Adsorption on Supported Gold Nanoparticle Catalysts: Application of the Temkin Model

A theoretical study of CO adsorption on gold by Hückel theory and density functional theory calculations

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