Direct versus Hydrogen-Assisted CO Dissociation

Shetty, SG Sharankumar; Jansen, Apj Tonek; Santen, Rutger A. van

doi:10.1021/ja9044482

Cited by 178 publications

(240 citation statements)

References 19 publications

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“…As it happens for Co and Fe, barriers on Ru catalysts for the unassisted reaction are much higher than those calculated after hydrogenation; this is the case of CO dissociation on the planar (111) terraces and also on low-coordination atoms at step-edge sites. The latter conclusions contrast with results arising from DFT/PW91 studies by van Santen and co-workers, concerning the CO dissociation on stepped Ru(101 � 5) [52], and on open Ru(112 � 1) [53] or Ru(101 � 0)B [54] surfaces, where calculated barriers for CO direct dissociation on low-coordinated sites are only 0.92 eV, 0.67 eV and 0.49 eV, respectively. The barriers on these three Ru surfaces are significantly smaller than that calculated for the reaction on the planar Ru(0001) surface, i.e., 2.35 eV [52]; such barriers are also smaller than those required to cleave the C-O bond via the hydroxymethylidyne or the formyl routes.…”

Section: Co* + H* → Coh* + * (3a)contrasting

confidence: 87%

Fischer-Tropsch Synthesis on Multicomponent Catalysts: What Can We Learn from Computer Simulations?

2015

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Abstract:In this concise review paper, we will address recent studies based on the generalized-gradient approximation (GGA) of the density functional theory (DFT) and on the periodic slab approach devoted to the understanding of the Fischer-Tropsch synthesis process on transition metal catalysts. As it will be seen, this computational combination arises as a very adequate strategy for the study of the reaction mechanisms on transition metal surfaces under well-controlled conditions and allows separating the influence of different parameters, e.g., catalyst surface morphology and coverage, influence of co-adsorbates, among others, in the global catalytic processes. In fact, the computational studies can now compete with research employing modern experimental techniques since very efficient parallel computer codes and powerful computers enable the investigation of more realistic molecular systems in terms of size and composition and to explore the complexity of the potential energy surfaces connecting reactants, to intermediates, to products of reaction. In the case of the Fischer-Tropsch process, the calculations were used to complement experimental work and to clarify the reaction mechanisms on different catalyst models, as well as the influence of additional components and co-adsorbate species in catalyst activity and selectivity.

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Section: Co* + H* → Coh* + * (3a)contrasting

confidence: 87%

Fischer-Tropsch Synthesis on Multicomponent Catalysts: What Can We Learn from Computer Simulations?

2015

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“…In addition, to CO direct dissociation, H atom was found to assist CO dissociation through the formation of intermediate formyl (CHO) on several metals. In the same way, Shetty and coworkers [22] have reported that for compact faces, CHO route is favorable, whereas for corrugated facets, CO direct dissociation might predominate. In the present work we have carried out comprehensive calculations within spin-polarized density functional theory (DFT), to study the dissociative adsorption of H 2 and the effect of the preadsorbed hydrogen in the CO adsorption on Fe(100) under (0, 1/3, 2/3) ML of hydrogen coverages.…”

Section: Introductionmentioning

confidence: 74%

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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“…3 Theoretical and experimental works to date suggest that a hydrogen-assisted pathway should be more favorable on close-packed surfaces, whereas the carbide mechanism is preferred on stepped and corrugated surfaces. 1,[4][5][6][7][8] Theoretical studies have provided support for dissociation via H x CO intermediates on Ru(0001) (Ref. 5) and Co(0001).…”

Section: Introductionmentioning

confidence: 99%

Evidence of stable high-temperature Dx-CO intermediates on the Ru(0001) surface

Ueta

Groot

Juurlink

et al. 2012

The Journal of Chemical Physics

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We demonstrate the formation of complexes involving attractive interactions between D and CO on Ru(0001) that are stable at significantly higher temperatures than have previously been reported for such intermediate species on this surface. These complexes are evident by the appearance of new desorption features upon heating of the sample. They decompose in stages as the sample temperature is increased, with the most stable component desorbing at >500 K. The D:CO ratio remaining on the surface during the final stages of desorption tends towards 1:1. The new features are populated during normally incident molecular beam dosing of D 2 on to CO pre-covered Ru(0001) surfaces (180 K) when the CO coverage exceeds 50% of the saturation value. The amount of complex formed decreases somewhat with increasing CO pre-coverage. It is almost absent in the case of dosing on to the fully saturated surface. The results are interpreted in terms of both local and long-range rearrangements of the overlayer that give rise to the observed CO coverage dependence and limit the amount of complex that can be formed.

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Direct versus Hydrogen-Assisted CO Dissociation

Cited by 178 publications

References 19 publications

Fischer-Tropsch Synthesis on Multicomponent Catalysts: What Can We Learn from Computer Simulations?

Fischer-Tropsch Synthesis on Multicomponent Catalysts: What Can We Learn from Computer Simulations?

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

Evidence of stable high-temperature Dx-CO intermediates on the Ru(0001) surface

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