The effects of the hydrophobic environment on proton mobility in perfluorosulfonic acid systems: an ab initio molecular dynamics study

Habenicht, Bradley F.; Paddison, Stephen J.; Tuckerman, Mark E.

doi:10.1039/c0jm00253d

Cited by 60 publications

(80 citation statements)

References 59 publications

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“…Following this, the band labeled (C-D) in the aqueous proton spectrum might indicate the presence of a lone hydronium ion in the states of higher compression (0.7, 0.9 nm) as indicated by the blue-shift of this (C-D) band as d decreases. This fact that hydronium species may replace Zundel cations (and/or Eigen complexes) was already observed by Habenicht et al [76] in their study of the effects of hydrophobic confinement on protons from acidic systems.…”

Section: Proton Spectroscopymentioning

confidence: 70%

Proton transfer in liquid water confined inside graphene slabs

Tahat

Martı́

2015

Phys. Rev. E

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The microscopic structure and dynamics of an excess proton in water constrained in narrow graphene slabs between 0.7 and 3.1 nm wide has been studied by means of a series of molecular dynamics simulations. Interaction of water and carbon with the proton species was modelled using a multistate empirical valence bond Hamiltonian model. The analysis of the effects of confinement on proton solvation structure and on its dynamical properties has been considered for varying densities. The system is organized in one interfacial and a bulk-like region, both of variable size.In the widest interplate separations, the lone proton shows a marked tendency to place itself in the bulk phase of the system, due to the repulsive interaction with the carbon atoms. However, as the system is compressed and the proton is forced to move to the vicinity of graphene walls it moves closer to the interface, producing a neat enhancement of the local structure. We found a marked slowdown of proton transfer when the separation of the two graphene plates is reduced. In the case of lowest distances between graphene plates (0.7 and 0.9 nm), only one-two water layers persist and the two-dimensional character of water structure becomes evident. By means of spectroscopical analysis, we observed the persistence of Zundel and Eigen structures in all cases, although at low interplate separations a signature frequency band around 2500 cm −1 suffers a blue-shift and moves to characteristical values of asymmetric hydronium ion vibrations, indicating some unstability of the typical Zundel-Eigen moieties and their eventual conversion to a single hydronium species solvated by water.

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Section: Proton Spectroscopymentioning

confidence: 70%

Proton transfer in liquid water confined inside graphene slabs

Tahat

Martı́

2015

Phys. Rev. E

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“…[27] Ab initio calculations by Liao and Li [28] suggest that intermolecular proton transfer is much easier between triflic acid and imidazole as compared to triflic acid and water. Recently, Habenicht et al [29,30] investigated the proton transfer in SO 3 H functionalized carbon nanotubes (CNT) at very low water content using ab initio molecular dynamics (AIMD) methods. The authors investigated the role of hydrogen bonding when proton transfers from the SO 3 H group in the presence of different hydrophobic CNT environments.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics simulations of triflic acid and triflate ion/water mixtures: A proton conducting electrolytic component in fuel cells

Sunda

Venkatnathan

2011

J Comput Chem

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Triflic acid is a functional group of perflourosulfonated polymer electrolyte membranes where the sulfonate group is responsible for proton conduction. However, even at extremely low hydration, triflic acid exists as a triflate ion. In this work, we have developed a force-field for triflic acid and triflate ion by deriving force-field parameters using ab initio calculations and incorporated these parameters with the Optimized Potentials for Liquid Simulations - All Atom (OPLS-AA) force-field. We have employed classical molecular dynamics (MD) simulations with the developed force field to characterize structural and dynamical properties of triflic acid (270-450 K) and triflate ion/water mixtures (300 K). The radial distribution functions (RDFs) show the hydrophobic nature of CF(3) group and presence of strong hydrogen bonding in triflic acid and temperature has an insignificant effect. Results from our MD simulations show that the diffusion of triflic acid increases with temperature. The RDFs from triflate ion/water mixtures shows that increasing hydration causes water molecules to orient around the SO(3)(-) group of triflate ions, solvate the hydronium ions, and other water molecules. The diffusion of triflate ions, hydronium ion, and water molecules shows an increase with hydration. At λ = 1, the diffusion of triflate ion is 30 times lower than the diffusion of triflic acid due to the formation of stable triflate ion-hydronium ion complex. With increasing hydration, water molecules break the stability of triflate ion-hydronium ion complex leading to enhanced diffusion. The RDFs and diffusion coefficients of triflate ions, hydronium ions and water molecules resemble qualitatively the previous findings using per-fluorosulfonated membranes.

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“…The structure and dynamics of hydrated protons has been studied by many authors by means of calculations at different levels of theory [e.g., ref. [22][23][24][25][26][27]. In this work, we focus specifically on the mechanism of the charge carrier transfer at graphene nanoribbon edges from a first principle computational point of view, considering both structural and electronic aspects.…”

Section: Introductionmentioning

confidence: 99%

Charge carrier exchange at chemically modified graphene edges: a density functional theory study

Liao

Sun

et al. 2012

J. Mater. Chem.

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Heteroatom doping on the edge of graphene may serve as an effective way to tune chemical activity of carbon-based electrodes with respect to charge carrier transfer in an aqueous environment. In a step towards developing mechanistic understanding of this phenomenon, we explore herein mechanisms of proton transfer from aqueous solution to pristine and doped graphene edges utilizing density functional theory. Atomic B-, N-, and O-doped edges as well as the native graphene are examined, displaying varying proton affinities and effective interaction ranges with the H 3 O + charge carrier. Our study shows that the doped edges characterized by more dispersive orbitals, namely boron and nitrogen, demonstrate more energetically favourable charge carrier exchange compared with oxygen, which features more localized orbitals. Extended calculations are carried out to examine proton transfer from the hydronium ion in the presence of explicit water, with results indicating that the basic mechanistic features of the simpler model are unchanged.

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The effects of the hydrophobic environment on proton mobility in perfluorosulfonic acid systems: an ab initio molecular dynamics study

Cited by 60 publications

References 59 publications

Proton transfer in liquid water confined inside graphene slabs

Proton transfer in liquid water confined inside graphene slabs

Molecular dynamics simulations of triflic acid and triflate ion/water mixtures: A proton conducting electrolytic component in fuel cells

Charge carrier exchange at chemically modified graphene edges: a density functional theory study

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