Mechanism of the Water Gas Shift Reaction on Pt:  First Principles, Experiments, and Microkinetic Modeling

Grabow, Lars C.; Gokhale, Amit A.; Evans, Steven T.; Dumesic, James A.; Mavrikakis, Manos

doi:10.1021/jp7099702

Cited by 470 publications

(706 citation statements)

References 48 publications

(85 reference statements)

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“…20 In summary, we corrected the enthalpy of O 2 adsorption using our more accurate reflectivity of 76% and show that it gives nearly identical results below 0.15 ML to the heats of adsorption determined from TPD experiments. 2,3 We further use these corrected adsorption enthalpies to amend the energetics of hydroxyl species on Pt (111) Fig.…”

Section: Enthalpies For Reactions Involving Surface Hydroxyls On Pt(111)mentioning

confidence: 73%

Energetics of Oxygen Adatoms, Hydroxyl Species and Water Dissociation on Pt(111)

Karp¹,

Campbell²,

Studt

et al. 2012

J. Phys. Chem. C

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Calorimetric measurements of the adsorption enthalpy of O 2,g to make 2 O ad on Pt(111) were performed by Fiorin et al..1 However, we show that they used a calibration value for the optical reflectivity of Pt(111) that was incorrectly reported in the literature. This error in reflectivity led to a 40% error in the adsorption energies originally reported. We use our more accurate reflectivity of 76% to recalibrate their oxygen adsorption enthalpy data and show that it gives nearly identical results below 0.15 ML to the heats of adsorption determined from the temperature programmed desorption (TPD) experiments of two separate groups (Campbell et al. 2 and Parker et al.3 ). Differences arise above 0.15 ML, but we attribute these to the very low sticking probability of O 2,g on Pt(111) (< 0.05) above 0.15ML, which can lead to large errors in the adsorption energies measured by calorimetry. Given this, we propose that the most reliable values for the adsorption enthalpy of oxygen on Pt(111) up to ¼ ML are those derived from TPD experiments, rather than the more recent calorimetry data. The best values are well described by (217-151θ) kJ/mol O 2 below ¼ ML, where θ is the O ad coverage in ML (i.e., O ad per Pt surface atom). We also report calculations of coverage-dependent adsorption energies for oxygen on Pt(111) from density functional theory (DFT) and find the results to be an average of 21 kJ/mol higher than the integral heats measured by TPD. We further use these corrected adsorption enthalpies to amend the energetics of hydroxyl species on Pt(111) that we previously measured 4 . This gives revised values for the standard enthalpies of formation of the coadsobed (D 2 O-OD) ad complex of -511 ± 7 kJ/mol and a Pt-OD bond energy of 248 ± 7 kJ/mol for the OD species within this complex. DFT compares reasonably well, calculating an enthalpy of formation for the (H 2 O-OH) ad complex of -456 kJ/mol and an O-Pt bond energy of 217 kJ/mol for the OH species within this complex. These revised values are used to estimate reaction enthalpies for the dissociation of adsorbed water and hydroxyl on Pt(111), and compared to DFT.

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Section: Enthalpies For Reactions Involving Surface Hydroxyls On Pt(111)mentioning

confidence: 73%

Energetics of Oxygen Adatoms, Hydroxyl Species and Water Dissociation on Pt(111)

Karp¹,

Campbell²,

Studt

et al. 2012

J. Phys. Chem. C

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“…~0.6 eV lower than direct dissociation. In principle, direct hydrogenation of CO 2 to formate (HCOO) could also occur but this involves a much higher energy barrier ( 58 or kinetic Monte Carlo 59 algorithms. Nevertheless, it is worth pointing out that kinetic experimental data and the theoretical energy barriers show similar trends.…”

Section: Computational Studymentioning

confidence: 99%

Highly Active Au/δ-MoC and Cu/δ-MoC Catalysts for the Conversion of CO₂: The Metal/C Ratio as a Key Factor Defining Activity, Selectivity, and Stability

et al. 2016

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The ever growing increase of CO 2 concentration in the atmosphere is one of the main causes of global warming. Thus, CO 2 activation and conversion towards valuable added compounds is a major scientific challenge. A new set of Au/δ-MoC and Cu/δ-MoC catalysts exhibits high activity, selectivity, and stability for the reduction of CO 2 to CO with some subsequent selective hydrogenation towards methanol. Sophisticated experiments under controlled conditions and calculations based on density functional theory have been used to study the unique behavior of these systems. A detailed comparison of the behavior of Au/β-Mo 2 C and Au/δ-MoC catalysts provides evidence of the impact of the metal/carbon ratio in the carbide on the performance of the catalysts. The present results show that this ratio governs the chemical behavior of the carbide and the properties of the admetal, up to the point of being able to switch the rate and mechanism of the process for CO 2 conversion. A control of the metal/carbon ratio paves the road for an efficient reutilization of this environmental harmful greenhouse gas.

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“…3,4 They found that formate, an intermediate involved in formic acid production, is a spectator species for the WGS reaction. The energy barriers for adding an adsorbed H atom to physisorbed CO 2 to form formate are 1.02 and 1.39 eV on Cu(111) and Pt(111), respectively.…”

Section: Introductionmentioning

confidence: 99%

CO₂ Hydrogenation to Formic Acid on Ni(111)

et al. 2012

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Periodic, self-consistent, density functional theory (DFT) calculations are employed to study CO 2 hydrogenation on Ni(111). CO 2 hydrogenation with H adsorbed on the surface and with H absorbed in the subsurface is investigated systematically and the respective microscopic reaction mechanisms are elucidated. We show that on Ni(111), CO 2 hydrogenation to formate intermediate is more favorable than to carboxyl intermediate. The hydrogenation to formate goes through the unidentate structure that rapidly transforms into the bidentate structure. Further hydrogenation from formate to formic acid is energetically more difficult than formate formation. Formation of adsorbed formic acid from adsorbed CO 2 and surface hydrogen is an endothermic reaction. Because subsurface H in Ni(111) is substantially less stable compared to surface H, its reaction with adsorbed CO 2 to adsorbed formic acid is an exothermic one. Our results may have significant implications for the synthesis of liquid fuels from CO 2 and for catalytic hydrogenation reactions in general.2

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Mechanism of the Water Gas Shift Reaction on Pt: First Principles, Experiments, and Microkinetic Modeling

Cited by 470 publications

References 48 publications

Energetics of Oxygen Adatoms, Hydroxyl Species and Water Dissociation on Pt(111)

Energetics of Oxygen Adatoms, Hydroxyl Species and Water Dissociation on Pt(111)

Highly Active Au/δ-MoC and Cu/δ-MoC Catalysts for the Conversion of CO₂: The Metal/C Ratio as a Key Factor Defining Activity, Selectivity, and Stability

CO₂ Hydrogenation to Formic Acid on Ni(111)

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Mechanism of the Water Gas Shift Reaction on Pt: First Principles, Experiments, and Microkinetic Modeling

Cited by 470 publications

References 48 publications

Energetics of Oxygen Adatoms, Hydroxyl Species and Water Dissociation on Pt(111)

Energetics of Oxygen Adatoms, Hydroxyl Species and Water Dissociation on Pt(111)

Highly Active Au/δ-MoC and Cu/δ-MoC Catalysts for the Conversion of CO2: The Metal/C Ratio as a Key Factor Defining Activity, Selectivity, and Stability

CO2 Hydrogenation to Formic Acid on Ni(111)

Contact Info

Product

Resources

About

Highly Active Au/δ-MoC and Cu/δ-MoC Catalysts for the Conversion of CO₂: The Metal/C Ratio as a Key Factor Defining Activity, Selectivity, and Stability

CO₂ Hydrogenation to Formic Acid on Ni(111)