Ab‐Initio calculations of the CO adsorption and dissociation on substitutional Fe–Cu surface alloys relevant to Fischer–Tropsch Synthesis: <i>bcc</i>‐(Cu)Fe(100) and <i>fcc</i>‐(Fe)Cu(100)

Elahifard, Mohammadreza; Fazeli, Elham; Joshani, Azadeh; Gholami, Majid

doi:10.1002/sia.5228

Cited by 18 publications

(13 citation statements)

References 46 publications

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“…57 These studies indicate an important dependence of reaction pathways on the surface composition and structure. Adding Cu into Fe modifies the surface electron distribution of the Fe catalyst, and the resulting change of catalyst composition and structure impacts the stability of reactants, intermediates, and transition states, 25,58,76,77 thus altering the dominant pathways.…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Insight into C–C Coupling over Fe–Cu Bimetallic Catalysts in CO₂ Hydrogenation

et al. 2017

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Density functional theory (DFT) calculations were carried out to investigate the mechanism of CO2 hydrogenation in production of C1 and C2 hydrocarbons over Cu–Fe bimetallic catalyst. CH* is found to be the most favorable monomeric species for production of CH4 and C2H4 via C–C coupling of two CH* species and subsequent hydrogenation. On the bimetallic Cu–Fe(100) surface at 4/9 ML Cu coverage, the energetically preferred path for CH* formation goes through CO2* → HCOO* → HCOOH* → HCO* → HCOH* → CH*, in which both the HCOO* → HCOOH* and HCO* → HCOH* steps have substantial barriers. The bimetallic surface suppresses CH4 formation and is more selective to C2H4 due to the higher hydrogenation barrier of CH2* species relative to those for C–C coupling and CH–CH* conversion to C2H4. On monometallic Fe(100) surface, CH* formation goes through a path of CO2* → CO* → HCO* → HCOH* → CH*, different from that identified on Cu–Fe(100). The hydrogenation of HCO* to HCOH* is the rate-limiting step that controls CO2 conversion to CH4 and C2H4. CH4 formation is kinetically more favored, with a 0.3 eV lower energy barrier, than C2H4 formation. The bimetallic combination of Cu and Fe enhances CO2 conversion by reducing the kinetic barriers, and alters the selectivity preference to more valuable C2H4 from CH4 on monometallic Fe surface. C2H6 can be produced from further hydrogenation of C2H4 with moderate barriers.

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Section: Resultsmentioning

confidence: 99%

Mechanistic Insight into C–C Coupling over Fe–Cu Bimetallic Catalysts in CO₂ Hydrogenation

et al. 2017

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“…The investigation of CO adsorption 19 and dissociation on the basis Fe/Cu surface alloy model 39,40 and Cu monolayer model on Fe surface 41 showed that Cu can re- Cu promotion were reported; and this might be partially due to the obscure of Cu existing way and the complex structures.…”

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confidence: 94%

Surface Morphology of Cu Adsorption on Different Terminations of the Hägg Iron Carbide (χ-Fe₅C₂) Phase

et al. 2015

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Spin-polarized density functional theory computations have been carried to investigate the surface morphology of 10 Cu n adsorption on the Fe 5 C 2 (100), Fe 5 C 2 (111), Fe 5 C 2 (510), Fe 5 C 2 (001) and Fe 5 C 2 (010) surface terminations in different surface Fe 11 and C ratios. On the Fe 5 C 2 (100), and Fe 5 C 2 (510) surfaces, aggregation is thermodynamically more favored than dispersion, while 12 dispersion is more favored than aggregation on the Fe 5 C 2 (111) surface for n = 2-4, on the Fe 5 C 2 (010) surface for n = 2 and on the 13 Fe 5 C 2 (001) surface for n = 2-4. The difference in structures and stability at low coverage depends on the stronger Cu-Fe interac-14 tion over the Cu-Cu interaction as well as the location of the adsorption sites. The adsorption energies do not correlate with the 15 surface Fe and C ratios. Comparison among the most stable Fe (110), Fe 3 C(001) and Fe 5 C 2 (100) surfaces reveals that the Fe (110) 16 surface has higher Cu affinity than the Fe 3 C(001) and Fe 5 C 2 (100) surfaces; and the carbide surfaces have close Cu affinities; in 17 agreement with the experimental observations. On all these iron and carbide surfaces, two-dimensional monolayer surface ad-18 sorption configurations are energetically more favored than the adsorption of three-dimensional Cu n clusters, and it can be ex- 19pected that the adsorbed Cu atoms should grow epitaxially as a layer-by-layer mode at the initial stage. On the metallic Fe(110), 20Fe (100), Fe(111) and Fe 3 C(010) surfaces, the adsorbed Cu atoms are negatively charged; while on the Fe 3 C(100), Fe 5 C 2 (100), 21Fe 5 C 2 (111), Fe 5 C 2 (010), and Fe 5 C 2 (001) surfaces, the adsorbed Cu atoms are positively charged. On the Fe 3 C(001) and Fe 5 C 2 (510) 22surfaces, the adsorbed Cu atoms mainly interacting with surface Fe atoms are very slightly negatively charged. This trend is in 23 line with their difference in electronegativity. Our results build the foundation for further study of Cu-promotion effect in 24Fe-based FTS in particular and for metal-doped heterogeneous catalysis in general. 25 26

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“…There have been extensive theoretical studies on CO hydrogenation for higher alcohol synthesis (HAS) over Fe-based catalysts, with a focus on adding Cu to promote the product selectivity. − Zhao et al investigated CO dissociation on Cu-doped Fe(100) surfaces and found that Cu doping reduces CO dissociation activity. An H-assisted dissociation path is more favorable than the direct dissociation path.…”

Section: Introductionmentioning

confidence: 99%

Computational Investigation of Fe–Cu Bimetallic Catalysts for CO₂ Hydrogenation

et al. 2016

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Density functional theory (DFT) calculations were carried out to investigate Fe−Cu bimetallic catalysts for the adsorption, activation, and initial hydrogenation of CO 2 . CO 2 adsorption strength decreases monotonically as surface Cu coverage increases. For dissociation of CO 2 , the reaction energy and activation barrier scale linearly with surface Cu coverage. The reaction energy becomes less exothermic, and the activation barrier increases with increasing surface Cu coverage from 0 to 1 ML. For initial hydrogenation of CO 2 , formation of a formate (HCOO*) intermediate is kinetically favored over carboxyl (COOH*) at all surface Cu coverages. A substantial decrease of the kinetic barrier for HCOO* formation is observed when surface Cu coverage increases to 4/9 ML. CO* is the preferred intermediate from CO 2 dissociation at 2/9 ML surface Cu coverage or below; however, the favorable conversion path changes to CO 2 hydrogenation to a HCOO* intermediate when surface Cu coverage increases to 4/9 ML or higher. The composition and structure of the bimetallic catalysts determine the preferred intermediates and dominant reaction paths for CO 2 conversion, and thus, both impact the catalytic activity and selectivity.

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Ab‐Initio calculations of the CO adsorption and dissociation on substitutional Fe–Cu surface alloys relevant to Fischer–Tropsch Synthesis: bcc‐(Cu)Fe(100) and fcc‐(Fe)Cu(100)

Cited by 18 publications

References 46 publications

Mechanistic Insight into C–C Coupling over Fe–Cu Bimetallic Catalysts in CO₂ Hydrogenation

Mechanistic Insight into C–C Coupling over Fe–Cu Bimetallic Catalysts in CO₂ Hydrogenation

Surface Morphology of Cu Adsorption on Different Terminations of the Hägg Iron Carbide (χ-Fe₅C₂) Phase

Computational Investigation of Fe–Cu Bimetallic Catalysts for CO₂ Hydrogenation

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Ab‐Initio calculations of the CO adsorption and dissociation on substitutional Fe–Cu surface alloys relevant to Fischer–Tropsch Synthesis: bcc‐(Cu)Fe(100) and fcc‐(Fe)Cu(100)

Cited by 18 publications

References 46 publications

Mechanistic Insight into C–C Coupling over Fe–Cu Bimetallic Catalysts in CO2 Hydrogenation

Mechanistic Insight into C–C Coupling over Fe–Cu Bimetallic Catalysts in CO2 Hydrogenation

Surface Morphology of Cu Adsorption on Different Terminations of the Hägg Iron Carbide (χ-Fe5C2) Phase

Computational Investigation of Fe–Cu Bimetallic Catalysts for CO2 Hydrogenation

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Mechanistic Insight into C–C Coupling over Fe–Cu Bimetallic Catalysts in CO₂ Hydrogenation

Mechanistic Insight into C–C Coupling over Fe–Cu Bimetallic Catalysts in CO₂ Hydrogenation

Surface Morphology of Cu Adsorption on Different Terminations of the Hägg Iron Carbide (χ-Fe₅C₂) Phase

Computational Investigation of Fe–Cu Bimetallic Catalysts for CO₂ Hydrogenation