Molecular Dynamics Study of Proton Transfer Including Grotthus Mechanism in Polymer Electrolyte Membrane

This paper describes characteristics of proton transfer in polymer electrolyte membrane by Molecular Dynamics (MD) simulation. Nafion was used as a membrane. Grotthus mechanism as well as Vehicle mechanism was considered in the simulation. To treat Grotthus mechanism, Empirical Valence Bond (EVB) method was used. The parameters or functions of the interaction potential of EVB method were determined so that potential energy barrier of proton hopping obtained by EVB method is consistent with that obtained by Density Functional Theory (DFT) and adjusted so that the diffusion coefficient of hydronium ion in water obtained by MD simulation is consistent with that of experimental results. After annealing the system, radial distribution function or mean square displacements of hydronium ion and water, which correspond to diffusivity of each compound, was obtained. These results show the nanoscale characteristics of proton transfer in polymer electrolyte membrane.

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A Molecular Dynamics Study for Diffusivity of Proton in Polymer Electrolyte Membrane

ASME/JSME 2011 8th Thermal Engineering Joint Conference ◽

10.1115/ajtec2011-44195 ◽

2011 ◽

Author(s):

Takashi Tokumasu ◽

Taiki Yoshida

Keyword(s):

Molecular Dynamics ◽

Proton Transfer ◽

Polymer Electrolyte ◽

Density Functional ◽

Md Simulation ◽

Polymer Electrolyte Membrane ◽

Valence Bond ◽

Electrolyte Membrane ◽

Hydronium Ion ◽

Grotthus Mechanism

This paper describes characteristics of proton transfer in polymer electrolyte membrane by Molecular Dynamics (MD) simulation. Nafion was used as a membrane. Grotthus mechanism as well as Vehicle mechanism was considered in the simulation. To treat Grotthus mechanism, Empirical Valence Bond (EVB) method was used. The parameters or functions of the interaction potential of EVB method were determined so that potential energy barrier of proton hopping obtained by EVB method is consistent with that obtained by Density Functional Theory (DFT) and adjusted so that the diffusion coefficient of hydronium ion in water obtained by MD simulation is consistent with that of experimental results. After annealing the system, radial distribution function or mean square displacements of hydronium ion and water, which correspond to diffusivity of each compound, was obtained. These results show the nanoscale characteristics of proton transfer in polymer electrolyte membrane.

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4-3 Molecular Dynamics Simulation of Proton Transfer in Polymer Electrolyte Membrane of PEFC

The Proceedings of the Symposium on Micro-Nano Science and Technology ◽

10.1299/jsmemnm.2011.3.41 ◽

2011 ◽

Vol 2011.3 (0) ◽

pp. 41-42

Author(s):

Takashi Tokumasu

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulation ◽

Proton Transfer ◽

Polymer Electrolyte ◽

Polymer Electrolyte Membrane ◽

Dynamics Simulation ◽

Electrolyte Membrane

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A Molecular Dynamics Study for the Characteristics of Proton Transfer in Polymer Electrolyte Membrane

ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 2, Fora ◽

10.1115/ajk2011-36021 ◽

2011 ◽

Author(s):

Takashi Tokumasu ◽

Taiki Yoshida

Keyword(s):

Molecular Dynamics ◽

Fuel Cell ◽

Proton Transfer ◽

Polymer Electrolyte ◽

Energy Barrier ◽

Density Functional ◽

Polymer Electrolyte Membrane ◽

Mean Square Displacement ◽

Polymer Electrolyte Fuel Cell ◽

Electrolyte Membrane

These days Polymer Electrolyte Fuel Cell (PEFC) is the most developed fuel cell. A polymer electrolyte membrane (PEM) is used in PEFC. Its efficiency is proportional to the proton transferring efficiency, which depends on the nanoscale structure of water. In this study, the property of proton transfer was analyzed by Molecular Dynamics (MD) method including Grotthus mechanism by Empirical Valence Bond (EVB) method. Nafion membrane was adopted as PEM. The potential energy barrier of proton hopping obtained by EVB method was adjusted to reproduce the energy barrier obtained by Density Functional Theory (DFT). In MD simulation, the distribution of water in Nafion was firstly analyzed. The results showed that liquid molecules gather around sulfo groups. Next, the property of proton transfer was analyzed by Mean Square Displacement (MSD).

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