scholarly journals Mechanistic investigation and free energies of the reactive adsorption of ethanol at the alumina/water interface

2021 ◽  
Author(s):  
Paul Clabaut ◽  
Jérôme Rey ◽  
Romain Réocreux ◽  
Stephan Steinmann ◽  
Carine Michel
Keyword(s):  
Water Interface ◽  
Free Energies ◽  
Reactive Adsorption ◽  
Mechanistic Investigation

The adsorption of lower trialkylphosphates at the dodecane – water interface

1980 ◽  
Vol 58 (24) ◽  
pp. 2789-2795 ◽  
Author(s):  
Norman H. Sagert ◽  
Woon Lee
Keyword(s):  
Equation Of State ◽  
Chain Length ◽  
Water Interface ◽  
Two Dimensional ◽  
Free Energies ◽  
Dimensional Solution ◽  
Interfacial Tensions ◽  
Enthalpy Of Adsorption ◽  
Solution Models ◽  
Methylene Group

The adsorption of tripropylphosphate, triethylphosphate, and trimethylphosphate at the dodecane–water interface has been studied at temperatures from 293 to 313 K. Standard free energies of adsorption were obtained from the lowering of interfacial tensions in the low (< 10−4) solute mole fraction region. Standard enthalpies and entropies of adsorption were then obtained from the temperature variation of the standard free energies of adsorption.Standard free energies of adsorption from dodecane showed little variation with solute chain length, with the exception of trimethylphosphate. On the other hand, free energies of adsorption from water decreased by 3.45 kJ/mol for each methylene group added, again with the exception of trimethylphosphate. Enthalpies of adsorption increased linearly with increasing solute chain length for adsorption from either phase. For each methylene group added, the enthalpy of adsorption from dodecane increased by 2.9 kJ/mol, while that from water increased by 2.4 kJ/mol.Results for tripropylphosphate adsorption and for triethylphosphate adsorption at higher temperatures could be adequately described by the Schofield–Rideal equation of state, but not by simple two-dimensional solution models. Results for trimethylphosphate adsorption and for triethylphosphate adsorption at lower temperatures could not be fitted adequately by either type of equation of state.

Solvation Free Energies and Adsorption Energies at the Metal/Water Interface from Hybrid QM-MM Simulations

2020 ◽  
Author(s):  
Paul Clabaut ◽  
Benjamin Schweitzer ◽  
Andreas Goetz ◽  
Carine Michel ◽  
Stephan Steinmann
Keyword(s):  
Free Energy ◽  
Adsorption Energy ◽  
Metallic Surface ◽  
Implicit Solvent ◽  
Water Interface ◽  
Free Energies ◽  
Hybrid Scheme ◽  
Aromatic Molecules ◽  
Solvent Model ◽  
Metal Water

Modeling adsorption at the metal/water interfaces is a corner-stone 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<sub>2</sub>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<sup>2</sup>) is in good agreement with the experimental estimate (-0.32 J/m<sup>2</sup>). 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.

The adsorption of tri-n-butylphosphate at the n-dodecane–water interface

1979 ◽  
Vol 57 (10) ◽  
pp. 1218-1223 ◽  
Author(s):  
Norman H. Sagert ◽  
Woon Lee ◽  
Michael J. Quinn
Keyword(s):  
Mole Fraction ◽  
Model Equation ◽  
Equations Of State ◽  
Water Interface ◽  
Two Dimensional ◽  
Free Energies ◽  
Dimensional Solution ◽  
Simple Version ◽  
Enthalpy Of Adsorption ◽  
Gas Laws

The adsorption of tri-n-butylphosphate (TBP) from n-dodecane to the n-dodecane–water interface has been studied as a function of TBP mole fraction up to 2.7 × 10−4 in the n-dodecane, and as a function of temperature from 293.15 K to 308.15 K. Free energies of adsorption were calculated from the results at low TBP mole fractions, where the surface pressures were linear with mole fraction. They were in the range −36.1 to −35.6 kJ/mol. The enthalpy of adsorption, determined from the variation of the free energies of adsorption with temperature, was −45.4 kJ/mol.Several equations of state based on two-dimensional gas laws were applied to the results. The Schofield–Rideal equation described the results adequately but the simpler Volmer equation was inadequate especially at lower temperatures. Deviations from the Volmer equation were in the direction of higher surface pressure. A simple version of the two-dimensional solution model equation of state was not helpful.

scholarly journals Solvation Free Energies and Adsorption Energies at the Metal/Water Interface from Hybrid QM-MM Simulations

2020 ◽  
Author(s):  
Paul Clabaut ◽  
Benjamin Schweitzer ◽  
Andreas Goetz ◽  
Carine Michel ◽  
Stephan Steinmann
Keyword(s):  
Free Energy ◽  
Adsorption Energy ◽  
Metallic Surface ◽  
Implicit Solvent ◽  
Water Interface ◽  
Free Energies ◽  
Hybrid Scheme ◽  
Aromatic Molecules ◽  
Solvent Model ◽  
Metal Water

Modeling adsorption at the metal/water interfaces is a corner-stone 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<sub>2</sub>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<sup>2</sup>) is in good agreement with the experimental estimate (-0.32 J/m<sup>2</sup>). 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.

The adsorption of tri-N-butylphosphate at the benzene–water interface

1982 ◽  
Vol 60 (10) ◽  
pp. 1244-1249 ◽  
Author(s):  
Norman H. Sagert ◽  
Woon Lee ◽  
Michael J. Quinn
Keyword(s):  
Gas Chromatography ◽  
Equations Of State ◽  
Adsorbed Layer ◽  
Distribution Coefficients ◽  
Vapor Pressure Osmometry ◽  
Water Interface ◽  
Free Energies ◽  
Drop Volume ◽  
Enthalpy Of Adsorption ◽  
Strong Adsorption

Adsorption of tri-n-butylphosphate (TBP) at the benzene–water interface was studied as a function of the TBP mole fraction in benzene up to 0.018 and at temperatures from 9 to 29 °C. The extent of adsorption was calculated from interfacial tension data obtained by the drop-volume technique. Standard free energies of adsorption from benzene ranged from −20.9 kJ/mol at 9 °C to −22.5 kJ/mol at 29 °C, giving a standard enthalpy of adsorption of +2.5 kJ/mol. Thus the strong adsorption occurs because of entropy changes. Distribution coefficients for the partition of TBP between benzene and water were measured by gas chromatography, and standard free energies of adsorption from water were derived. They ranged from −44.8 kJ/mol at 9 °C to −51.1 kJ/mol at 29 °C, with standard enthalpies of adsorption ranging from 74 to 15 kJ/mol over the same temperature range.Results at higher mole fractions were fitted to various equations of state, after using vapor pressure osmometry (at 37 °C) to determine that activity corrections were small. The Schofield–Rideal equation described the results adequately, with A0 close to 1.0 nm2 and/close to 1.0 at lower temperatures. These values imply that lateral repulsion between TBP molecules in the adsorbed layer is minimal.

scholarly journals Solvation Free Energies and Adsorption Energies at the Metal/Water Interface from Hybrid QM-MM Simulations

2020 ◽  
Author(s):  
Paul Clabaut ◽  
Benjamin Schweitzer ◽  
Andreas Goetz ◽  
Carine Michel ◽  
Stephan Steinmann
Keyword(s):  
Free Energy ◽  
Adsorption Energy ◽  
Metallic Surface ◽  
Implicit Solvent ◽  
Water Interface ◽  
Free Energies ◽  
Hybrid Scheme ◽  
Aromatic Molecules ◽  
Solvent Model ◽  
Metal Water

Modeling adsorption at the metal/water interfaces is a corner-stone 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<sub>2</sub>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<sup>2</sup>) is in good agreement with the experimental estimate (-0.32 J/m<sup>2</sup>). 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.

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