Ab Initio Molecular Dynamics Study of the Reaction of Water with Formaldehyde in Sulfuric Acid Solution

Sprik, Michiel; Meijer, Evert Jan

doi:10.1021/ja972935u

Cited by 92 publications

(68 citation statements)

References 48 publications

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“…First, we used constrained molecular dynamics to evaluate the free energies of activation for CH 3 OH dehydrogenation on uncharged, Pt(111) without solvation using a Blue Moon Ensemble (15)(16)(17)(18)(19)(20) as described in detail in Methods. This is analogous to vapor-phase methanol dehydrogenation.…”

Section: Resultsmentioning

confidence: 99%

“…Here, we use ab initio (constrained) molecular dynamics (AIMD) to study the effect of water solvent reorganization and substrate charge toward methanol electrooxidation on a model Pt surface, Pt(111). In particular, we use a Blue Moon Ensemble (15)(16)(17)(18)(19)(20) to evaluate the free energy of activation for breaking the C−H and O−H bonds in methanol. This systematic study applies AIMD to a heterogeneously catalyzed reaction accounting for both solvent and charged surfaces.…”

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confidence: 99%

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Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces

Herron

Morikawa

Mavrikakis

2016

Proc. Natl. Acad. Sci. U.S.A.

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Using ab initio molecular dynamics as implemented in periodic, self-consistent (generalized gradient approximation PerdewBurke-Ernzerhof) density functional theory, we investigated the mechanism of methanol electrooxidation on Pt(111). We investigated the role of water solvation and electrode potential on the energetics of the first proton transfer step, methanol electrooxidation to methoxy (CH 3 O) or hydroxymethyl (CH 2 OH). The results show that solvation weakens the adsorption of methoxy to uncharged Pt(111), whereas the binding energies of methanol and hydroxymethyl are not significantly affected. The free energies of activation for breaking the C−H and O−H bonds in methanol were calculated through a Blue Moon Ensemble using constrained ab initio molecular dynamics. Calculated barriers for these elementary steps on unsolvated, uncharged Pt(111) are similar to results for climbing-image nudged elastic band calculations from the literature. Water solvation reduces the barriers for both C−H and O−H bond activation steps with respect to their vapor-phase values, although the effect is more pronounced for C−H bond activation, due to less disruption of the hydrogen bond network. The calculated activation energy barriers show that breaking the C−H bond of methanol is more facile than the O−H bond on solvated negatively biased or uncharged Pt(111). However, with positive bias, O−H bond activation is enhanced, becoming slightly more facile than C−H bond activation.ethanol presents a promising fuel alternative to hydrogen for low-temperature polymer electrolyte membrane fuel cells (1, 2). However, the slower reaction kinetics, compared with hydrogen, requires high overpotentials, which reduces the overall energy efficiency of these fuel cells. Additionally, CO molecules that are formed during the reaction poison Pt catalysts, limiting their activity (2). To address this problem, improved electrocatalysts must be developed (3, 4). Toward this goal, it is essential to understand the sequence of elementary steps that comprise the reaction mechanism. Through knowledge of the detailed mechanism on a particular catalyst, one can determine the ratedetermining step(s). In turn, this information can be used to design improved catalysts that are targeted toward facilitating the rate-determining step.First-principles density functional theory (DFT) calculations have become invaluable for working toward understanding these detailed reaction mechanisms at the atomic scale. In particular, these methods have successfully been used to calculate the thermochemistry (reaction energies) and kinetics (activation energy barriers) of a variety of different catalytic reactions in the vapor phase. However, modeling electrocatalytic reactions poses a greater challenge due to the complexity of the reaction environment at the active site. That is, the reaction occurs on a charged substrate that is surrounded by solvent (and electrolyte). A variety of methods have been developed to model the effects of solvent and charged surfaces on the thermo...

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces

Herron

Morikawa

Mavrikakis

2016

Proc. Natl. Acad. Sci. U.S.A.

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“…This is a linear combination of the above reaction coordinates, and it constrains the difference between these two distances. It is particularly convenient for studying proton transfer in hydrogen bonding, 50 and it allows changes in the angle spanned by the two distance vectors (in this case P-P-O w ). In addition to dynamical information obtained by constraining reaction coordinates, one must know the related change in free energy (work), and we adopt a widely used technique where the mean averaged force f s is integrated with respect to the reaction coordinate Q, The force f s (Q) is obtained via the forces of constraint.…”

Section: Methods Of Calculationmentioning

confidence: 99%

ATP Hydrolysis in Water − A Density Functional Study

2003

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Adenosine 5′-triphosphate (ATP) is a basic energy carrier in cellular metabolism. As a high-energy intermediate, it provides a way to convert energy from one biochemical process to another via an environment-dependent hydrolysis reaction. Two paths for ATP hydrolysis in water with Mg 2+ are studied here using the density functional method: an associative reaction involving a nucleophilic attack of one water molecule, and a dissociative reaction involving a scission of the terminal bridging P-O bond. The latter has an activation energy of 35 kcal/mol, where 25 kcal/mol can be assigned to the P-O bond breaking and 10 kcal/mol to the artificial stability of PO 3 -resulting from the small size and the short time scale of the simulation. The path and energy barrier (39 kcal/mol) of the less-favorable associative reaction suggest that it is possible only under conditions where the lytic water is already deprotonated to OH -. The Mg cation elongates the terminal bridging P-O bond when forming a bidentate chelate with the two terminal phosphates. Additional constrained displacements of Mg 2+ with respect to the nearest phosphate oxygens show that a direct electrophilic attack of Mg toward a bridging O is possible.

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“…(1) Since the idea behind is the RDF-free energy relation, it should be precise enough for the distance constraint, which controls the distance between two particles (Meijer and Sprik, 1998). However, in coordination constrained simulations, the constraint force also acts on the other protons besides the leaving one.…”

Section: Mean Force Free Energy and Pkamentioning

confidence: 99%

Acid dissociation mechanisms of Si(OH)4 and Al(H2O)63+ in aqueous solution

Liu

Meijer

et al. 2010

Geochimica et Cosmochimica Acta

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Silicic acid and the hexa-aqua of Al 3+ are fundamental model aqueous species of chemical importance in nature. In order to investigate their hydroxyl dissociation mechanisms, Car-Parrinello molecular dynamics (CPMD) simulations were carried out, which allow treating the solutes and solvents on the same footing. The method of constraint was employed to trigger the reactions by taking coordination number as the reaction coordinate and the thermodynamic integration was used to obtain the free-energy profiles. The approximate transition states were located and the reactant and product states were also characterized. The free-energy changes of dissociation are found about 15.0 kcal/mol and 7.7 kcal/mol for silicic acid and Al-aqua, respectively. From the simulation results, the first pKas were calculated by using two approaches, which are based on the pristine thermodynamic relation and the RDF (radial distribution function)-free energy relation, respectively. Because of more uncertainties involved in the RDF way, it is suggested that the pristine way should be favored, which shows an error margin of 1 pKa unit. This study provides an encouraging basis for applying the present methodology to predict acidity constants of those groups that are difficult to measure experimentally.

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Ab Initio Molecular Dynamics Study of the Reaction of Water with Formaldehyde in Sulfuric Acid Solution

Cited by 92 publications

References 48 publications

Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces

Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces

ATP Hydrolysis in Water − A Density Functional Study

Acid dissociation mechanisms of Si(OH)4 and Al(H2O)63+ in aqueous solution

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