Hydrogenation mechanism of carbon dioxide and carbon monoxide on Ru(0001) surface: a density functional theory study

Zhang, Shitong; Yan, Hong; Wei, Min; Evans, David G.; Duan, Xue

doi:10.1039/c4ra01655f

Cited by 70 publications

(128 citation statements)

References 58 publications

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“…75,76 The corresponding H−Pt distance (1.834 Å) is slightly shorter than that of H−Ru (1.917 and 1.942 Å). The adsorption energy (−2.86 eV) of H on the alloy surface is lower than the theoretical value of −3.15 eV on Ru(0001), 56 but is close to that of −2.58 eV on PdZn(111). 46 3.2.…”

Section: Resultsmentioning

confidence: 51%

“…The alloying strengthens the adsorption of CHO with the adsorption energy of −2.70 eV, as compared to the values for pure Pt(111) (−2.36 eV) and Ru(0001) (−2.46 eV). 53,56 Different from the hollow site adsorption on Pt(111) 53 and Pd(111), 69 carbon monoxide tends to upright adsorb via the C atom atop a Ru atom on PtRu(111); the C− Ru distance is 1.868 Å. The adsorption energy in this case (−2.10 eV) falls in between the values for Pt(111) (−1.82 eV) and Ru(0001) (−2.30 eV), 53,56 similar to the situation of PtAu(111).…”

Section: Resultsmentioning

confidence: 98%

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The Oxidation of Methanol on PtRu(111): A Periodic Density Functional Theory Investigation

et al. 2015

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Self-consistent periodic density functional theory (PW91-GGA) calculations are employed to study the oxidation of methanol on PtRu(111). Geometries and energies for all the intermediates involved are analyzed, and the oxidation network is mapped out to illustrate the reaction mechanism. On PtRu(111), the Ru atoms with less electronegativity are more favorable to binding the adsorbates than the Pt atoms. Alloying Pt with Ru weakens the bond of CO to Pt, but strengthens the bond of CO to Ru. All possible pathways through initial C−H, O−H, and C−O bond scissions are considered. The initial O−H bond scission is found to be the most favorable and bears an energy barrier comparable to that for methanol desorption. The further oxidation occurs preferentially via the non-CO path from species CHO. The most possible reaction pathway of methanol on PtRu (111) Furthermore, the activation of H 2 O on PtRu(111) is more favorable than that on the pure Pt(111) surface. The enhancement of methanol oxidation catalytic activity of the PtRu alloy is due primarily to altering the major reaction pathways from the CO path on pure Pt to the non-CO path on the alloy surface as well as promoting adsorption of methanol and formation of active OH species from H 2 O.

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Section: Resultsmentioning

confidence: 51%

Section: Resultsmentioning

confidence: 98%

The Oxidation of Methanol on PtRu(111): A Periodic Density Functional Theory Investigation

et al. 2015

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“…13,36 Recent density functional theory calculations, however, showed that the dissociation barrier of C−O bond is lower in COH (or CHO) intermediate than in CO(ads). 41 Our results seem to suggest that further hydrogenation of CO LF proceeds through an intermediate containing C, O, and H (e.g., formyl) rather than a direct dissociation pathway on Pd/Al 2 O 3 . The rate-limiting step for CH 4 formation is proposed to be the C−O bond breaking in the CO LF species with hydrogen assistance.…”

Section: Resultsmentioning

confidence: 74%

Mechanism of CO₂ Hydrogenation on Pd/Al₂O₃ Catalysts: Kinetics and Transient DRIFTS-MS Studies

et al. 2015

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The hydrogenation of CO 2 was investigated over a wide range of reaction conditions, using two Pd/γ-Al 2 O 3 catalysts with different Pd loadings (5% and 0.5%) and dispersions (∼11% and ∼100%, respectively). Turnover rates for CO and CH 4 formation were both higher over 5% Pd/Al 2 O 3 with a larger average Pd particle size than those over 0.5% Pd/Al 2 O 3 with a smaller average particle size. The selectivity to methane (22−40%) on 5% Pd/Al 2 O 3 was higher by a factor of 2−3 than that on 0.5% Pd/Al 2 O 3 . The drastically different rate expressions and apparent energies of activation for CO and CH 4 formation led us to conclude that reverse water gas shift and CO 2 methanation do not share the same rate-limiting step on Pd and that the two pathways are probably catalyzed at different surface sites. Measured reaction orders in CO 2 and H 2 pressures were similar over the two catalysts, suggesting that the reaction mechanism for each pathway does not change with particle size. In accordance, the DRIFTS results reveal that the prevalent surface species and their evolution patterns are comparable on the two catalysts during transient and steady-state experiments, switching feed gases among CO 2 , H 2 , and CO 2 + H 2 . The DRIFTS and MS results also demonstrate that no direct dissociation of CO 2 takes place over the two catalysts and that CO 2 has to first react with surface hydroxyls on the oxide support. The thus-formed bicarbonates react with dissociatively adsorbed hydrogen on Pd particles to produce adsorbed formate species (bifunctional catalyst: CO 2 activation on the oxide support and H 2 dissociation on the metal particles). Formates near the Pd particles (most likely at the metal/oxide interface) can react rapidly with adsorbed H to produce CO, which then adsorbs on the metallic Pd particles. Two types of Pd sites are identified: one has a weak interaction with CO, which easily desorbs into gas phase at reaction temperatures, whereas the other interacts more strongly with CO, which is mainly in multibound forms and remains stable in He flow at high temperatures, but is reactive toward adsorbed H atoms on Pd leading eventually to CH 4 formation. 5% Pd/Al 2 O 3 contains a larger fraction of terrace sites favorable for forming these more multibound and stable CO species than 0.5% Pd/Al 2 O 3 . Consequently, we propose that the difference in the formation rate and selectivity to CH 4 on different Pd particle sizes stems from the different concentrations of the reactive intermediate for the methanation pathway on the Pd surface.

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“…As mentioned earlier, CO methanation on Ni was negligible, indicating that a methanation reaction was probably not taking place on the Ni surface. 2 Their result showed that the reaction pathway for CO methanation proceeds via either a COH or a CHO intermediate from CO dissociation, resulting in active C and CH species, respectively. 8A and B), the adsorption bands at 2170 and 2110 cm -1 were observed for both mZSM5 and Ni/mZSM5 catalysts, which can be assigned to the gaseous CO. A band at 1625 cm -1 was observed on mZSM5, which was assigned to atomic hydrogen.…”

Section: Mechanistic Investigation Of Co Methanationmentioning

confidence: 99%

Nickel-promoted mesoporous ZSM5 for carbon monoxide methanation

et al. 2015

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Nickel-promoted mesoporous ZSM5 (Ni/mZSM5) was prepared for CO methanation. XRD, NMR and SEM analysis confirmed the structural stability of Ni/mZSM5 with coffin type morphology. The nitrogen physisorption and pyrrole adsorbed FTIR analyses indicated the presence of micro-mesoporosity and a moderate amount of basic sites on both mZSM5 and Ni/mZSM5. At 623 K, Ni/mZSM5 showed a high rate of CO conversion (141.6 μmol CO/ gcat s) and 92% CH4 yield. Ni/mZSM5 showed better catalytic performance than Ni/MSN (82.4 μmol CO/ g-cat s, 82% CH4 yield), Ni/HZSM5 (29.0 μmol CO/ g-cat s, 54.5% CH4 yield), and Ni/γ-Al2O3 (14.5 μmol CO/ g-cat s, 38.6% CH4 yield). It is noteworthy that the superior catalytic performance of Ni/mZSM5 could be attributed to the presence of both micromesoporosity and basicity, which led to a synergistic effect of Ni m etal active sites and the mZSM5 support. In situ FTIR spectroscopy showed that CO and H2 may be adsorbed on Ni metal followed by spillover to form adsorbed CO and adsorbed H on the mZSM5 surface. Then, two possible mechanisms for CO methanation were proposed. In the first mechanism, the adsorbed CO may be reacted with H2 to form CH4 and H2O. In the second mechanism, the adsorbed H may be reacted with CO to form CH4 and CO2. However, in this case, the former is the predominant pathway as the methanation reaction is favored by inhibition of the water-gas shift reaction.

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Hydrogenation mechanism of carbon dioxide and carbon monoxide on Ru(0001) surface: a density functional theory study

Cited by 70 publications

References 58 publications

The Oxidation of Methanol on PtRu(111): A Periodic Density Functional Theory Investigation

The Oxidation of Methanol on PtRu(111): A Periodic Density Functional Theory Investigation

Mechanism of CO₂ Hydrogenation on Pd/Al₂O₃ Catalysts: Kinetics and Transient DRIFTS-MS Studies

Nickel-promoted mesoporous ZSM5 for carbon monoxide methanation

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Hydrogenation mechanism of carbon dioxide and carbon monoxide on Ru(0001) surface: a density functional theory study

Cited by 70 publications

References 58 publications

The Oxidation of Methanol on PtRu(111): A Periodic Density Functional Theory Investigation

The Oxidation of Methanol on PtRu(111): A Periodic Density Functional Theory Investigation

Mechanism of CO2 Hydrogenation on Pd/Al2O3 Catalysts: Kinetics and Transient DRIFTS-MS Studies

Nickel-promoted mesoporous ZSM5 for carbon monoxide methanation

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Resources

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Mechanism of CO₂ Hydrogenation on Pd/Al₂O₃ Catalysts: Kinetics and Transient DRIFTS-MS Studies