Effects of postdosed species on preadsorbed carbon monoxide on iron (100):  adsorption site conversion caused by site competition

Lu, Jiong Ping; Albert, M.R.; Bernasek, Steven L.

doi:10.1021/j100378a074

Cited by 21 publications

(22 citation statements)

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“…FTS technology has become important because of the rapid hydrocarbon resource depletion, the unpredictable prices of crude oil, the increased fuel demands worldwide, and the environmental regulations. Among many transition metals having FTS activity, iron-based catalysts are preferred due to their low price, high activity, and low CH 4 selectivity [2] [3]. Several experimental techniques have been used to investigate the adsorption of CO on Fe (100).…”

Section: Introductionmentioning

confidence: 99%

Effect of Hydrogen in Adsorption and Direct Dissociation of CO on Fe (100) Surface: A DFT Study

Amaya-Roncancio¹,

Linares²,

Duarte³

et al. 2015

AJAC

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Density functional theory was employed to investigate the effect of the hydrogen in the adsorption and direct dissociation of CO on Fe (100) surface. The preadsorption of hydrogen with coverages of 0, 1/3 and 2/3 monolayer (ML) was used in the present investigation. In the case of 1/3 ML of hydrogen, two configurations of adsorption were studied. The presence of hydrogen shows a major transference of electronic density from Fe surface to CO adsorbed, increasing the adsorption energy of CO from 2.00 eV in clean surface, to 2.76 eV in 2/3 ML of hydrogen. Furthermore, the activation barrier for direct dissociation of CO was 1.13 eV and for the recombination energy 2.28 eV on clean Fe (100) surface. In the same way, the activation barrier for CO in the presence of coadsorbed hydrogen was slightly affected presenting values of 1.06 eV and 1.16 eV to 1/3 ML configurations and 0.98 eV for 2/3 ML of hydrogen. Finally, the recombination energy decreases to 1.63 eV and 1.49 eV for 1/3 ML configurations and to 1.23 eV for 2/3 ML of coadsorbed hydrogen. These results indicate that the CO adsorption and dissociation are favored in the presence of hydrogenated surfaces.

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Section: Introductionmentioning

confidence: 99%

Effect of Hydrogen in Adsorption and Direct Dissociation of CO on Fe (100) Surface: A DFT Study

Amaya-Roncancio¹,

Linares²,

Duarte³

et al. 2015

AJAC

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“…5-8 X-ray photoelectron spectroscopy (XPS) together with low energy electron diffraction (LEED) resolved the stoichiometry and branching ratios between molecular desorption and dissociation in the dissociation reaction. 6,9 Vibrational electron energy loss spectroscopy (EELS) studies 7,8,10 showed typical vibrational frequencies a) Author to whom correspondence should be addressed. Electronic mail:…”

Section: Introductionmentioning

confidence: 99%

X-ray emission spectroscopy and density functional study of CO/Fe(100)

Gladh

Öberg

et al. 2012

The Journal of Chemical Physics

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We report x-ray emission and absorption spectroscopy studies of the electronic structure of the predissociative α(3) phase of CO bound at hollow sites of Fe(100) as well as of the on-top bound species in the high-coverage α(1) phase. The analysis is supported by density functional calculations of structures and spectra. The bonding of "lying down" CO in the hollow site is well described in terms of π to π∗ charge transfer made possible through bonding interaction also at the oxygen in the minority spin-channel. The on-top CO in the mixed, high-coverage α(1) phase is found to be tilted due to adsorbate-adsorbate interaction, but still with bonding mainly characteristic of "vertical" on-top adsorbed CO similar to other transition-metal surfaces.

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“…Furthermore, the MC and MO stretches are 533 and 389 cm −1 at 0.25 ML, and 548 and 404 cm −1 at 0.5 ML. The experimental MC and MO stretches appear around 520 and 400 cm −1 2…”

Section: Resultsmentioning

confidence: 91%

“…Although the TPD spectra only show the β desorption state, CO is adsorbed molecularly and dissociates upon heating above 400 K. Increasing the CO coverage results in the appearance of a second desorption state labeled α 3 , which corresponds to the CO molecules tilted on the surface at fourfold hollow sites. The saturation coverage of the α 3 state is 0.5 ML and at this coverage it is suggested that half of the CO(α 3 ) molecules dissociate when the temperature is increased above 440 K, while the other half desorb 2. 3 Using the Redhead equation and assuming a pre‐exponential factor of 10 13 , Moon et al5 reported an adsorption energy of the CO molecules in the α 3 state of 26.3 kcal mol −1 (≈1.14 eV).…”

Section: Resultsmentioning

confidence: 99%

“…The dissociation of the CO molecule is a key step in the Fischer–Tropsch reaction and, consequently, it has attracted a lot of attention from both a fundamental and an industrial point of view. Several experimental techniques have been used to investigate the adsorption of CO on Fe(100), which offers the advantage of structural simplicity with respect to the more open Fe(111) surface or Fe(110); these techniques include temperature‐programmed desorption (TPD),1–5 electron‐energy loss spectroscopy (EELS),2, 4, 6 X‐ray photoelectron spectroscopy (XPS),1, 2, 4, 5 ultraviolet photoelectron spectroscopy (UPS),3 X‐ray photoelectron diffraction (XPD),7 and near‐edge X‐ray absorption fine structure (NEXAFS) 4. 8, 9 On the other hand, theoretical studies are scarce and date from the 80s and early 90s and were carried out using semiempirical10, 11 or Hartree–Fock12 methods.…”

Section: Introductionmentioning

confidence: 99%

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