Direct versus Hydrogen‐Assisted CO Dissociation on the Fe (100) Surface: a DFT Study

Elahifard, Mohammad Reza; Jigato, Manuel Pérez; Niemantsverdriet, J.W.

doi:10.1002/cphc.201100759

Cited by 57 publications

(64 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The activation energy (E Forward ) of CO dissociation on clean Fe (100) was 1.13 eV ( Table 2) and the recombination energy (E Back ) was 2.28 eV showing the exothermic nature of the dissociation process ( Table 2). The IS, TS and FS at 0 ML coverage of H are in good agreement with the other reported calculations of Wang et al [31], Tracy et al [32], Xun-hua et al [33], and Elahifard et al [37]. The direct dissociation of CO in the presence of coadsorbed H present slight variations of forward barrier to all coverages studied, where 1.06 eV, 1.16 eV and 0.90 eV were found for 1/3-asymmetric, 1/3-symmetric and 2/3 ML of H, respectively.…”

Section: Direct Dissociation Of Co In Presence Of Hydrogensupporting

confidence: 91%

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

View full text Add to dashboard Cite

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.

show abstract

Section: Direct Dissociation Of Co In Presence Of Hydrogensupporting

confidence: 91%

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

View full text Add to dashboard Cite

show abstract

“…Thus, as similarly concluded on Fe [41,42], Co [28,30] and Ru [27] surfaces, H-assisted CO dissociation through formation of an HCO intermediate is kinetically favoured over the COH mechanism. Comparison of direct and H-assisted CO dissociation pathways based on DFT calculations has been made on pure iron surfaces [20,[41][42][43][44][45] and to a lesser extent on surfaces of Hägg iron carbide [53][54][55][56]. On Fe(100) [41] and Fe(110) [20] it was argued that both direct and H-assisted CO dissociation paths can contribute under FT reaction conditions, although on Fe(110) sequential hydrogenation of CO to form a hydroxymethylene (HCOH) species was postulated at higher CO surface coverages [20].…”

Section: H-assisted Co Dissociation On Fe-terminatedsupporting

confidence: 53%

“…On the Fe(100) surface, direct CO dissociation was calculated to have a lower overall energy barrier than H-assisted dissociation via a formyl (HCO) intermediate, while COH formation was energetically unfavourable and not competitive [41]. It was concluded that both the direct and H-assisted path via HCO formation could contribute depending on the reaction conditions.…”

Section: Introductionmentioning

confidence: 98%

CO Dissociation at Vacancy Sites on Hägg Iron Carbide: Direct Versus Hydrogen-Assisted Routes Investigated with DFT

Petersen

Rensburg

2015

Top Catal

View full text Add to dashboard Cite

The mechanism of activation of CO remains under debate in Fe-catalysed Fischer-Tropsch synthesis, in which iron carbides form under reaction conditions. Direct and H-assisted paths for CO activation and dissociation are investigated at carbon vacancy and non-vacancy sites on the Fe 5 C 2 (010) surface of Hägg iron carbide using density functional theory. The calculated overall energy barrier for direct and for H-assisted dissociation of CO via formation of an HCO intermediate is the same, 1.42 and 1.41 eV, respectively, but the lowest energy paths are facilitated by different vacancy sites. Furthermore, dissociation at a nonvacancy site is only marginally higher in energy by 0.1 eV. Dissociation through formation of a hydroxymethylidyne (COH) intermediate is less competitive kinetically.

show abstract

“…This energy rep-resents the energy barrier for dissociation and we can see that it follows the same pattern as the relative energy of the final minimum corresponding to the dissociated state. We know that the transition state represents the C-O bond severing by catalytic reaction with Fe [5,11,13]. From an electronic structure perspective, there are two simultaneous mechanisms that enable the C-O bond severing: 1) binding of the C atoms with strong covalent bonds to the most stable configuration (in this case hollow site) on the Fe surface and 2) compensation of the high electron affinity of the O atom by charge transfer from the surface to the O atom [15].…”

Section: Finite-size Effect On Dissociationmentioning

confidence: 99%

“…After almost a decade, this topic has been revisited by many researchers in recent years [10,11,[13][14][15]26]. There are several reasons for this renewed interest, of which, notable from the perspective of computational science, is the advancement in computational power that is necessary for surface calculations with the computationally demanding nudged elastic band method.…”

Section: Introductionmentioning

confidence: 99%

Insights on finite size effects in ab initio study of CO adsorption and dissociation on Fe 110 surface

Chakrabarty

Bouhali

Mousseau

et al. 2016

Journal of Applied Physics

View full text Add to dashboard Cite

Adsorption and dissociation of hydrocarbons on metallic surfaces represent crucial steps on the path to carburization, eventually leading to dusting corrosion. While adsorption of CO molecules on Fe surface is a barrier-less exothermic process, this is not the case for the dissociation of CO into C and O adatoms and the diffusion of C beneath the surface, that are found to be associated with large energy barriers. In practice, these barriers can be affected by numerous factors that combine to favour the CO-Fe reaction such as the abundance of CO and other hydrocarbons as well as the presence of structural defects. From a numerical point of view, studying these factors is challenging and a step-by-step approach is necessary to assess, in particular, the influence of the finite box size on the reaction parameters for adsorption and dissociation of CO on metal surfaces. Here, we use density functional theory (DFT) total energy calculations with the climbing-image nudged elastic band (CI-NEB) method to estimate the adsorption energies and dissociation barriers for different CO coverages with surface supercells of different sizes. We further compute the effect of periodic boundary condition for DFT calculations and find that the contribution from van der Waals interaction in the computation of adsorption parameters is important as they contribute to correcting the finite-size error in small systems. The dissociation process involves carbon insertion into the Fe surface causing a lattice deformation that requires a larger surface system for unrestricted relaxation. We show that, in the larger surface systems associated with dilute CO-coverages, Cinsertion is energetically more favourable, leading to a significant decrease in the dissociation barrier. This observation suggests that a large surface system with dilute coverage is necessary for all similar metal-hydrocarbon reactions in order to study their fundamental electronic mechanisms, as an isolated phenomenon, free from finite-size effects.

show abstract

Direct versus Hydrogen‐Assisted CO Dissociation on the Fe (100) Surface: a DFT Study

Cited by 57 publications

References 24 publications

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

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

CO Dissociation at Vacancy Sites on Hägg Iron Carbide: Direct Versus Hydrogen-Assisted Routes Investigated with DFT

Insights on finite size effects in ab initio study of CO adsorption and dissociation on Fe 110 surface

Contact Info

Product

Resources

About