This paper studies the transport phenomena inside the electrolyte of proton exchange membrane fuel cells (PEMFCs) using atomistic simulation techniques. The investigated material of the electrolyte is Nafion®, which is the most widely adapted polymer membrane in low-temperature fuel cells. The molecular dynamics simulation system includes part of the Nafion structure, numerous water molecules, and the transporting cations. The cations are assumed to be hydroxoniums (H3O+), which are a hydrogen proton combined with a water molecule. Simulation results indicated that the electrostatic energy dominated the other potential energies in the total internal energy analysis. Clusters of water molecules tend to move toward the sulfonic acid group in the Nafion fragment, where the hydrophilic/hydrophobic characteristics can be observed. The transport phenomena of hydroxoniums are classified into two categories—continuous migration and noncontinuous hopping. The self-diffusion coefficients of the hydroxoniums and the water molecules in the membrane were evaluated to be 3.476×105cm2s and 4.993×105cm2s respectively, based on the Einstein relation. The calculated self-diffusion coefficients are of the same order of magnitude as the experimental results, which indicates this atomistic simulation is reaching more and more practical in engineering analysis.

1.
USDOE
, 2004,
Fuel Cell Handbook
,
7th ed.
,
U.S. Department of Energy
, Morgantown, WV.
2.
Ennari
,
J.
,
Elomaa
,
M.
,
Neelov
,
I.
, and
Sundholm
,
F.
, 2000, “
Modeling of Water-Free and Water Containing Solid Polyelectrolytes
,”
Polymer
0032-3861,
41
(
3
), pp.
985
990
.
3.
Jinnouchi
,
R.
, and
Okazaki
,
K.
, 2003, “
Molecular Dynamics Study of Transport Phenomena in Perfluorosulfonate Ionomer Membranes for Polymer Electrolyte Fuel Cells
,”
J. Electrochem. Soc.
0013-4651,
150
(
1
), pp.
E66
E73
.
4.
Elliott
,
J. A.
,
Hanna
,
S.
,
Elliot
,
A. M. S.
, and
Cooley
,
G. E.
, 1999, “
Atomistic Simulation and Molecular Dynamics of Model Systems for Perfluorinated Ionomer Membranes
,”
Phys. Chem. Chem. Phys.
1463-9076,
1
(
20
), pp.
4855
4863
.
5.
Vishnyakov
,
A.
, and
Neimark
,
A. V.
, 2000, “
Molecular Dynamics Simulation of Nafion Oligomer Salvation in Equimolar Methanol-Water Mixture
,”
J. Phys. Chem. B
1089-5647,
105
(
32
), pp.
7830
7834
.
6.
Jang
,
S. S.
,
Molinero
,
V.
,
Cagin
,
T.
, and
Goddard
, III
W. A.
, 2004, “
Nanophase-Segregation and Transport in Nafion 117 From Molecular Dynamics Simulation: Effect of Monomeric Sequence
,”
J. Phys. Chem. B
1089-5647,
108
(
10
), pp.
3149
3157
.
7.
Hypercube
, 2002,
HyperChem Reference Manual
.
8.
Berendsen
,
H. J. C.
,
Grigera
,
J. R.
, and
Straatsma
,
T. P.
, 1987, “
The Missing Term in Effective Pair Potentials
,”
J. Phys. Chem.
0022-3654,
91
(
24
), pp.
6269
6271
.
9.
Allen
,
M. P.
, and
Tildesley
,
D. J.
, 1987,
Computer Simulation of Liquids
,
Clarendon
, Oxford.
10.
Mayo
,
S. L.
,
Olfason
,
B. D.
, and
Goddard
,
W. A.
, 1990, “
DREIDING: A Generic Force Field for Molecular Simulations
,”
J. Phys. Chem.
0022-3654,
94
(
24
), pp.
8897
8909
.
11.
Smith
,
W.
,
Leslie
,
M.
, and
Forester
,
T. R.
, 2003,
The DLPOLY2 User Manual
,
CCLRC
, Daresbury Laboratory.
12.
Berendsen
,
H. J. C.
,
Postma
,
J. P. M.
,
van Gunsteren
,
W.
,
DiNola
,
A.
, and
Haak
,
J. R.
, 1984, “
Molecular Dynamics With Coupling to an External Bath
,”
J. Chem. Phys.
0021-9606,
81
(
8
), pp.
3684
3690
.
13.
Verlet
,
L.
, 1967, “
Computer ‘Experiment’ on Classical Fluids. I. Thermodynamical Properties of Lennard-Jones Molecules
,”
Phys. Rev.
0031-899X,
159
, pp.
98
10
.
14.
Ryckaert
,
J. P.
,
Ciccotti
,
G.
, and
Berendsen
,
H. J. C.
, 1977, “
Numerical Integration of the Cartesian Equations of Motion of a System With Constraints: Molecular Dynamics of n-Alkanes
,”
J. Comput. Phys.
0021-9991,
23
, pp.
327
341
.
15.
Laaksonen
,
L.
, 1992, “
A Graphics Program for the Analysis and Display of Molecular Dynamics Trajectories
,”
J. Mol. Graphics
0263-7855,
10
, pp.
33
34
.
16.
Kreuer
,
K. D.
, 1997, “
On the Development of Proton Conducting Materials for Technological Applications
,”
Solid State Ionics
0167-2738,
97
, pp.
1
15
.
You do not currently have access to this content.