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

Hartshorn, Heather; Pursell, Christopher J.; Chandler, Bert D.

doi:10.1021/jp902553n

Cited by 39 publications

(62 citation statements)

References 44 publications

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“…44,62,63 K R should be strictly interpreted in terms the total reactivity of adsorbed O 2 ; this can only correspond to a maximum value for the O 2 binding constant (K R is inversely related to the equilibrium binding constant). The Ni-Au data show dramatic increases in K R relative to pure Au.…”

Section: Resultsmentioning

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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Section: Resultsmentioning

confidence: 99%

Enhanced Oxygen Activation over Supported Bimetallic Au−Ni Catalysts

et al. 2010

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“…CO-adsorption infrared experiments were performed as described previously 49 . Approximately 25 mg of the sample were pressed into a 30 × 30 mesh Ti wire cloth (Unique Wire Weaving Co.) and mounted into a custom-built copper cell and vacuum chamber with a gas-phase optical-path length of 1.2 cm.…”

Section: Methodsmentioning

confidence: 99%

Controlling activity and selectivity using water in the Au-catalysed preferential oxidation of CO in H2

et al. 2016

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“…CO adsorption experiments were performed as previously described [50,51]. Briefly, approximately 25 mg of a pretreated sample was pressed into a 30 Â 30 Ti mesh (Unique Wire Weaving Co.).…”

Section: Co Heat Of Adsorption Measurements Via Ir Spectroscopymentioning

confidence: 99%

“…The entire gashandling system was rinsed with CO three times before exposing the sample. After collecting a background spectrum, the sample was exposed to a low pressure of CO and the surface was allowed to equilibrate for 5-10 min; previous work has shown that this is ample time for CO equilibration on Au catalysts [48,50,51]. An infrared spectrum was recorded and the pressure in the cell was slowly increased to the next pressure.…”

Section: Co Heat Of Adsorption Measurements Via Ir Spectroscopymentioning

confidence: 99%

“…Infrared spectroscopy can be used to quantify CO adsorption on Au catalysts and extract thermodynamic metrics for CO binding [48,50,51]; in this case, we used the CO adsorption metric to evaluate potential changes to the Au particles. Details of the data collection and analysis can be found in separate publications [48,50,51].…”

Section: Infrared Spectroscopy Of Co Adsorptionmentioning

confidence: 99%

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CO oxidation over Au/TiO2 catalyst: Pretreatment effects, catalyst deactivation, and carbonates production

Lopez

Powell

Panthi

et al. 2013

Journal of Catalysis

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a b s t r a c tA commercially available Au/TiO 2 catalyst was subjected to a variety of thermal treatments in order to understand how variations in catalyst pretreatment procedures might affect CO oxidation catalysis. Catalytic activity was found to be inversely correlated to the temperature of the pretreatment. Infrared spectroscopy of adsorbed CO experiments, followed by a Temkin analysis of the data, indicated that the thermal treatments caused essentially no changes to the electronics of the Au particles; this, and a series of catalysis control experiments, and previous transmission electron microscopy (TEM) studies ruled out particle growth as a contributing factor to the activity loss. Fourier transform infrared (FTIR) spectroscopy showed that pretreating the catalyst results in water desorption from the surface, but the observable water loss was similar for all the treatments and could not be correlated with catalytic activity. A Michaelis-Menten kinetic treatment indicated that the main reason for deactivation is a loss in the number of active sites with little changes in their intrinsic activity. In situ FTIR experiments during CO oxidation showed extensive buildup of carbonate-like surface species when the pretreated catalysts were contacted with the feed gas. A semi-quantitative infrared spectroscopy method was developed for comparing the amount of carbonates present on each catalyst; results from these experiments showed a strong correlation between the steady-state catalytic activity and amount of surface carbonates generated during the initial moments of catalysis. Further, this experimental protocol was used to show that the carbonates reside on the titania support rather than on the Au, as there was no evidence that they poison Au-CO binding sites. The role of the carbonates in the reaction scheme, their potential role in catalyst deactivation, and the role of surface hydroxyls and water are discussed.

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

Cited by 39 publications

References 44 publications

Enhanced Oxygen Activation over Supported Bimetallic Au−Ni Catalysts

Enhanced Oxygen Activation over Supported Bimetallic Au−Ni Catalysts

Controlling activity and selectivity using water in the Au-catalysed preferential oxidation of CO in H2

CO oxidation over Au/TiO2 catalyst: Pretreatment effects, catalyst deactivation, and carbonates production

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