Inner-shell photoelectron spectroscopy of size-selected Cu-clusters on Si

Ferretti, N.; Balkaya, B.; Vollmer, Antje; Neeb, M.; Eberhardt, W.

doi:10.1016/j.elspec.2006.11.017

Cited by 13 publications

(12 citation statements)

References 23 publications

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“…Moreover, a displacement to higher BE (by 0.5-1 eV) with decreasing metal particle size (from bulk ? Cu 3 cluster) has been reported elsewhere for Cu clusters deposited on a silicon wafer [43]. In this work more than 30 % of the total Cu content in the lower loaded sample exhibited sizes \2 nm, which can contribute to the positive Cu 2p 3/2 BE shift.…”

Section: Catalyst Characterisationmentioning

confidence: 72%

‘‘Hydrogen-Free’’ Hydrogenation of Nitrobenzene Over Cu/SiO2 Via Coupling with 2-Butanol Dehydrogenation

Hao

Cárdenas‐Lizana

et al. 2014

Top Catal

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The feasibility of a coupled reaction system for the simultaneous production of 2-butanone (from 2-butanol dehydrogenation) and aniline (from nitrobenzene hydrogenation) over Cu/SiO 2 in continuous gas phase operation without an external H 2 supply has been established. Two (15.9 and 1.8 % w/w) Cu/SiO 2 catalysts were prepared by deposition-precipitation and characterised in terms of N 2 physisorption, temperature programmed reduction (TPR), H 2 chemisorption, powder XRD, STEM and XPS analysis. Following TPR, the higher Cu loading showed a wider particle size distribution (1-15 nm, mean 7.8 nm) than 1.8 % w/w Cu/SiO 2 (1-6 nm, mean 3.1 nm), where the latter exhibited a modified electronic character based on XPS measurements and a (fourfold) higher H 2 uptake capacity. The reactions showed antipathetic (dehydrogenation) and sympathetic (hydrogenation) structure sensitivity in terms of turnover frequency (TOF) dependence on Cu size. We have achieved, for the first time, 100 % yield to both target products (2-butanone and aniline) with appreciably (by a factor of 50) enhanced hydrogen utilisation in the coupled system relative to conventional nitrobenzene reduction using pressurised H 2 . Our results establish in situ hydrogen generation via catalytic dehydrogenation as a viable hydrogenation route to commercially important products.

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Section: Catalyst Characterisationmentioning

confidence: 72%

‘‘Hydrogen-Free’’ Hydrogenation of Nitrobenzene Over Cu/SiO2 Via Coupling with 2-Butanol Dehydrogenation

Hao

Cárdenas‐Lizana

et al. 2014

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“…2(a) , the general line-shape of S 2 p spectrum of the S-hyperdoped Si samples is shifted to a higher BE (0.3–0.5 eV) than that of pure S and their characteristic features are broader, owing to a change in the chemical environment of the S-dopant in the Si matrix. Also, S species in the sample have more chemically inequivalent atoms than the reference S 22 . Clearly, as shown in Tab.…”

Section: Resultsmentioning

confidence: 99%

Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques

Limaye

Chen

Lee

et al. 2015

Sci Rep

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The correlation between sub-band gap absorption and the chemical states and electronic and atomic structures of S-hyperdoped Si have been extensively studied, using synchrotron-based x-ray photoelectron spectroscopy (XPS), x-ray absorption near-edge spectroscopy (XANES), extended x-ray absorption fine structure (EXAFS), valence-band photoemission spectroscopy (VB-PES) and first-principles calculation. S 2p XPS spectra reveal that the S-hyperdoped Si with the greatest (~87%) sub-band gap absorption contains the highest concentration of S2− (monosulfide) species. Annealing S-hyperdoped Si reduces the sub-band gap absorptance and the concentration of S2− species, but significantly increases the concentration of larger S clusters [polysulfides (Sn2−, n > 2)]. The Si K-edge XANES spectra show that S hyperdoping in Si increases (decreased) the occupied (unoccupied) electronic density of states at/above the conduction-band-minimum. VB-PES spectra evidently reveal that the S-dopants not only form an impurity band deep within the band gap, giving rise to the sub-band gap absorption, but also cause the insulator-to-metal transition in S-hyperdoped Si samples. Based on the experimental results and the calculations by density functional theory, the chemical state of the S species and the formation of the S-dopant states in the band gap of Si are critical in determining the sub-band gap absorptance of hyperdoped Si samples.

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“…4) corresponds to an excitonic feature related to the excitation of a 2p electron to the open d-shell, thus being characteristic of a 3d 9 state, as expected for Cu 2+ cations. [26][27][28][29][30][31] In turn, the feature at 934.5 eV can be due to Cu + or metallic Cu. [26][27][28][29][30][31] The spectra appear similar to those reported previously for small monodispersed metallic copper clusters (Cu n -n = 10-55, d r 1.06 nm) deposited on silica and subjected to aeration upon which they become appreciably oxidized.…”

Section: Xps/aes/xanes Resultsmentioning

confidence: 99%

Near-ambient XPS characterization of interfacial copper species in ceria-supported copper catalysts

Monte

Munuera

Costa

et al. 2015

Phys. Chem. Chem. Phys.

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Catalysts based on combinations of copper and cerium oxides are interesting alternatives to noble metal ones for processes involved in the production/purification of hydrogen produced from hydrocarbons or biomass like the water-gas shift or the preferential oxidation of CO reactions. Active sites for such processes have been proposed to correspond to reduced species formed at the interface between both oxides. The present work provides direct evidence of reduced copper species located at the interface and observed during the course of near-ambient XPS experiments performed over samples of copper oxide supported on ceria nanospheres and nanocubes subjected to interaction with CO at different temperatures. The analysis of XPS results is based on DFT+U calculations employed as a complementary method for the analysis of redox properties of the catalysts and core-level shifts produced upon such redox changes. Differences observed in interfacial redox properties as a function of the ceria support morphology appear to be most useful to explain catalytic properties of this type of system for mentioned processes.

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Inner-shell photoelectron spectroscopy of size-selected Cu-clusters on Si

Cited by 13 publications

References 23 publications

‘‘Hydrogen-Free’’ Hydrogenation of Nitrobenzene Over Cu/SiO2 Via Coupling with 2-Butanol Dehydrogenation

‘‘Hydrogen-Free’’ Hydrogenation of Nitrobenzene Over Cu/SiO2 Via Coupling with 2-Butanol Dehydrogenation

Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques

Near-ambient XPS characterization of interfacial copper species in ceria-supported copper catalysts

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