Effects of an electric field on a water bilayer on Ag(111)

Zhao, Jinbin; Chan, Che Ting; Che, Jingguang

doi:10.1103/physrevb.75.085435

Cited by 31 publications

(19 citation statements)

References 34 publications

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“…In addition, the PES is affected by the orientation of water molecules. As already shown by Sánchez, 49 Zhao et al, 50 and Rossmeisl et al, 28 the orientation of water molecules depends 34 on the external field. In the bilayer model, half of the water molecules lie parallel to the surface, and the -OH bonds in the other half of the water molecules are pointing toward the vacuum (H-up, Figure 4a) or the surface (H-down, Figure 4b).…”

Section: Resultsmentioning

confidence: 56%

Density-Functional Analysis of Hydrogen on Pt(111): Electric Field, Solvent, and Coverage Effects

Hamada

Morikawa

2008

J. Phys. Chem. C

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Density-functional theory is utilized to study the energetics and vibrational properties of hydrogen on the Pt(111) surface in order to clarify the adsorption state of hydrogen on a Pt electrode in an electrochemical condition. Particular attention is paid to the Pt-H stretching frequency (ν Pt-H ) of hydrogen on the atop site, which is often referred to as overpotentially deposited hydrogen and considered to be the reaction intermediate of the hydrogen evolution reaction. We investigate the origin of the large potential dependence of ν Pt-H observed in the electrochemical experiments by taking into account the effects of electric field, solvent, and hydrogen coverage to simulate water/metal electrode interfaces realistically. The electric field effect on ν Pt-H without water solvent, the Stark tuning rate, is less than 20 cm -1 · V -1 . Although it is increased by a factor of 2.5 by taking into account the solvent effect, the electric field effect alone cannot account for the experimentally observed large potential-dependent frequency shift. It is found that the coverage effect on ν Pt-H is significant indicating that the electric field, solvent, and hydrogen coverage effects should be taken into account to explain fully the experimentally observed large frequency dependence on the electrode potential. The large hydrogen coverage effect on the vibration frequency shift is attributed to the shift of the d-band center due to the hybridization between the hydrogen s state and the substrate d-band.

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Section: Resultsmentioning

confidence: 56%

Density-Functional Analysis of Hydrogen on Pt(111): Electric Field, Solvent, and Coverage Effects

Hamada

Morikawa

2008

J. Phys. Chem. C

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“…[16][17][18] Because the binding strength of the metal dopants and H 2 molecules on the system is dominantly determined by their charge transfer, the external electric field which can redistribute the charges of the system is expected to be effective to control the adsorption and desorption process. [19][20][21][22] In addition, since graphene, which is commonly used as a substrate of storage material, has proved to exhibit a remarkable response to the perpendicular external electric field due to its high electronic behavior, the effect of an electric field on the system may be noticeable. 23 Therefore, the external electric field can act as a simple and efficient switch for hydrogen storage by regulating its direction and strength.…”

Section: Introductionmentioning

confidence: 99%

Enhanced hydrogen storage properties under external electric fields of N-doped graphene with Li decoration

Lee

Chung

2013

Phys. Chem. Chem. Phys.

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In this article, the imposition of an external electric field is proposed as an effective means to improve the hydrogen storage properties of a promising medium. To demonstrate the feasibility of this concept, the geometric stability and hydrogen capacity of Li functionalized N-doped graphene were investigated in the presence of an electric field using density functional theory (DFT) calculations. For Li decorated pristine and graphitic structures, the binding energy of the Li atom on the surface sheets exceeded the cohesive energy of the Li metal bulk under a positive electric field. From these results, Li adatom dispersion with atomic accuracy is expected for these two unstable structures. Furthermore, the hydrogen adsorption behavior of the pyridinic and pyrrolic structures was changed by the applied electric field in the range of 0.14-0.27 eV. It is therefore anticipated that the adsorption and desorption processes can be easily controlled using suitable field strength and direction.

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“…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 thermochemistry and kinetics of electrocatalytic reactions (5)(6)(7)(8)(9)(10)(11)(12)(13), and the strengths of these approaches were summarized in a recent publication (13).…”

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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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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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Effects of an electric field on a water bilayer on Ag(111)

Cited by 31 publications

References 34 publications

Density-Functional Analysis of Hydrogen on Pt(111): Electric Field, Solvent, and Coverage Effects

Density-Functional Analysis of Hydrogen on Pt(111): Electric Field, Solvent, and Coverage Effects

Enhanced hydrogen storage properties under external electric fields of N-doped graphene with Li decoration

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

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