Energetics of Adsorbed Phenol on Ni(111) and Pt(111) by Calorimetry

Carey, Spencer J.; Zhao, Wei; Mao, Zhongtian; Campbell, Charles T.

doi:10.1021/acs.jpcc.8b03155

Cited by 38 publications

(75 citation statements)

References 30 publications

(67 reference statements)

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“…Thus, the rate constant for adsorption decreases with increase in temperature; or, alternatively, low temperatures are favorable to promote the adsorption process. Whilst comparable literature for guaiacol is unavailable, σ for phenol is very close to unity at 90 K over Pt (111) and at 150 K over Ni (111) 54 , which agrees with the temperature of 160 K below which unity is observed in our calculations for guaiacol. In contrast, over a Ag (111) surface, σ for phenol is 0.56 at 163 K 55 , which is 0.20 lower than our sticking coefficient at a similar temperature (0.76 at 170 K).…”

Section: Resultssupporting

confidence: 89%

“…Once formed, the desorption of phenol from the surface is kinetically slow (3.49×10 1 s -1 at 500 K) and energy demanding (Edes = 4.45 eV), which means it would be likely to accumulate on the surface. The adsorption energy, which can be calculated as the negative of the desorption energy, suggests that the adsorption of phenol on the surface is at least 2 eV stronger than that observed over transition metals 54,55,[61][62][63] . Thus, the accumulated phenol could convert further to benzene, which is considered further herein via two mechanisms.…”

Section: Energy Profile Of the Upgrading Routesmentioning

confidence: 97%

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Hydrodeoxygenation of Guaiacol Over Orthorhombic Molybdenum Carbide: A DFT and Microkinetic Study

Agrawal

Roldan²,

Kishore³

et al. 2021

Preprint

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The hydrodeoxygenation of guaiacol is modelled over a (100) β-Mo2C surface using density functional theory and microkinetic simulations. The thermochemistry of the process shows that the demethoxylation of the guaiacol, to form phenol, will be the initial steps, with a reaction energy of 29 kJ/mol (i.e. endothermic) and a highest activation barrier of 112 kJ/mol. Subsequently, the dehydroxylation of the phenol, which has a rate-determining activation barrier of 145 kJ/mol, will lead to the formation of benzene, with an overall reaction energy for conversion from guaiacol of -91 kJ/mol (i.e. exothermic). The sp2 and sp hybridized carbon atoms of the molecular functional groups are found to dissociate on the surface with minimum energy barriers, while the hydrogenation of the adsorbed molecules requires higher energy. The microkinetic modelling, which is performed considering typical reaction conditions of 500 to 700 K, and a partial pressure ratio H2:guaiacol of 1, shows quick formation and accumulation of phenol on the surface with increasing temperature, although high temperatures mitigate the guaiacol adsorption step. Based on simulated temperature programmed desorption (TPD), maximum conversion of guaiacol can be expected at 70% surface coverage of this species.

show abstract

Section: Resultssupporting

confidence: 89%

Section: Energy Profile Of the Upgrading Routesmentioning

confidence: 97%

Hydrodeoxygenation of Guaiacol Over Orthorhombic Molybdenum Carbide: A DFT and Microkinetic Study

Agrawal

Roldan²,

Kishore³

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Thus, the rate constant for adsorption decreases with increase in temperature; or, alternatively, low temperatures are favorable to promote the adsorption process. Whilst comparable literature for guaiacol is unavailable, σ for phenol is very close to unity at 90 K over Pt (111) and at 150 K over Ni (111) 56 , which agrees with the temperature of 160 K below which unity is observed in our calculations for guaiacol. In contrast, over a Ag (111) surface, σ for phenol is 0.56 at 163 K 57 , which is 0.20 lower than our sticking coefficient at a similar temperature (0.76 at 170 K).…”

Section: Resultssupporting

confidence: 89%

“…Once formed, the desorption of phenol from the surface is kinetically slow (3.49×10 1 s -1 at 500 K) and energy demanding (Edes = 4.45 eV), which means it would be likely to accumulate on the surface. The adsorption energy, which can be calculated as the negative of the desorption energy, suggests that the adsorption of phenol on the surface is at least 2 eV stronger than that observed over transition metals 56,57,[65][66][67] . Thus, the accumulated phenol could convert further to benzene, which is considered further herein via two mechanisms.…”

Section: Energy Profile Of the Upgrading Routesmentioning

confidence: 97%

Hydrodeoxygenation of Guaiacol Over Orthorhombic Molybdenum Carbide: A DFT and Microkinetic Study

Agrawal

Roldán

Kishore

et al. 2021

Preprint

View full text Add to dashboard Cite

The hydrodeoxygenation of guaiacol is modelled over a (100) β-Mo2C surface using density functional theory and microkinetic simulations. The thermochemistry of the process shows that the demethoxylation of the guaiacol, to form phenol, will be the initial steps, with a reaction energy of 29 kJ/mol (i.e. endothermic) and a highest activation barrier of 112 kJ/mol. Subsequently, the dehydroxylation of the phenol, which has a rate-determining activation barrier of 145 kJ/mol, will lead to the formation of benzene, with an overall reaction energy for conversion from guaiacol of -91 kJ/mol (i.e. exothermic). The sp 2 and sp hybridized carbon atoms of the molecular functional groups are found to dissociate on the surface with minimum energy barriers, while the hydrogenation of the adsorbed molecules requires higher energy.The microkinetic modelling, which is performed considering typical reaction conditions of 500 to 700 K, and a partial pressure ratio H2:guaiacol of 1, shows quick formation and accumulation of phenol on the surface with increasing temperature, although high temperatures mitigate the guaiacol adsorption step. Based on simulated temperature programmed desorption (TPD), maximum conversion of guaiacol can be expected at 70% surface coverage of this species.

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“…[3][4][5][6][7] Furthermore, Pt(111)/water is one of the few solid/liquid interfaces for which a couple of experimental solvation energies are available. [8][9][10] We herein will rely on this exceptionally well-characterized interface to validate our general approach by comparing our computed adsorption energies at the solid/liquid interface to the available experimental values.…”

Section: Introductionmentioning

confidence: 99%

Solvation Free Energies and Adsorption Energies at the Metal/Water Interface from Hybrid Quantum-Mechanical/Molecular Mechanics Simulations

Clabaut

Schweitzer

Götz

et al. 2020

J. Chem. Theory Comput.

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Modeling adsorption at the metal/water interfaces is a cornerstone towards an improved understanding in a variety of fields from heterogeneous catalysis to corrosion. We propose and validate a hybrid scheme that combines the adsorption free energies obtained in gas phase at the DFT level with the variation in solvation from the bulk phase to the interface evaluated using a molecular mechanics based alchemical transformation, denoted MMsolv. Using the GAL17 force field for the platinum/water interaction, we retrieve a qualitatively correct interaction energy of the water solvent at the interface. This interaction is of near chemisorption character and thus challenging, both for the alchemical transformation, but also for the fixed point-charge electrostatics. Our scheme passes through a state characterized by a well-behaved physisorption potential for the Pt(111)/H 2 O interaction to converge the free energy difference. The workflow is implemented in the freely available SolvHybrid package. We first assess the adsorption of a water molecule at the Pt/water interface, which turns out to be a stringent test. The intrinsic error of our QM-MM hybrid scheme is limited to 6 kcal/mol through the introduction of a correction term to attenuate the electrostatic interaction between near-chemisorbed water molecules and the underlying Pt atoms. Next, we show that the MMsolv solvation free energy of Pt (-0.46 J/m 2) is in good agreement with the experimental estimate (-0.32 J/m 2). Furthermore, we show that the entropy contribution at room temperature is roughly of equal magnitude as the free energy, but with opposite sign. Finally, we compute the adsorption energy of benzene and phenol at the Pt(111)/water interface, one of the rare systems for which experimental data are available. In qualitative agreement with experiment, but in stark contrast with a standard implicit solvent model, the adsorption of these aromatic molecules is strongly reduced (i.e., less exothermic by ~30 and 40 kcal/mol for our QM/MM hybrid scheme and experiment, respectively, but ~0 with the implicit solvent) at the solid/liquid compared to the solid/gas interface. This reduction is mainly due to the competition between the organic adsorbate and the solvent for adsorption on the metallic surface. The semi-quantitative agreement with experimental estimates for the adsorption energy of aromatic molecules thus validates the soundness of our hybrid QM-MM scheme. File list (2) download file view on ChemRxiv SolvHybrid.pdf (20.52 MiB) download file view on ChemRxiv SI-SolvHybrid.pdf (705.65 KiB)

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Energetics of Adsorbed Phenol on Ni(111) and Pt(111) by Calorimetry

Cited by 38 publications

References 30 publications

Hydrodeoxygenation of Guaiacol Over Orthorhombic Molybdenum Carbide: A DFT and Microkinetic Study

Hydrodeoxygenation of Guaiacol Over Orthorhombic Molybdenum Carbide: A DFT and Microkinetic Study

Hydrodeoxygenation of Guaiacol Over Orthorhombic Molybdenum Carbide: A DFT and Microkinetic Study

Solvation Free Energies and Adsorption Energies at the Metal/Water Interface from Hybrid Quantum-Mechanical/Molecular Mechanics Simulations

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