Performance of Hydrogen Fuel Cell MEAs Based
on Perfluorinated Nanocomposite Membranes
Modified by Polyaniline
A. Munar,
a
K. Suarez,
b
O. Solorza,
b,
*
N. P. Berezina,
c
and V. Compañ
d,e,z
a
Departamento de Física, Universitat Jaume I, 12072 Castellón, Spain
b
Departamento de Química, Centro de Investigación y de Estudios Avanzados-Instituto Politécnico
Nacional, 07360 México DF, Mexico
c
Department of Physical Chemistry, Kuban State University, Krasnodar 350040, Russia
d
Departamento de Termodinámica Aplicada, Universidad Politécnica de Valencia, 46022 Valencia, Spain
e
Instituto de Tecnología Eléctrica, Parque Tecnológico de Valencia, 46980 Paterna, Spain
This work summarizes the results obtained from the modification of perfluorinated sulfocationic MF-4SC membranes by in situ
polymerization of aniline. The transport properties of polyaniline/MF-4SC composite membranes after different times of poly-
merization have been analyzed. It is observed that after 3 h of aniline polymerization, composite membranes exhibit higher
protonic conductivity compared to the pristine sample. The performance of fuel cells containing membrane electrode assemblies
MEAs from MF-4SC and polyaniline/MF-4SC has also been studied. The kinetic parameters governing the voltage dependence
on current density have been estimated and the results have been fitted to a previously established one-dimensional isothermal
model by Springer et al. J. Electrochem. Soc. 138, 2334 1991. Good agreement between experimental data and model has been
found for low density currents. Some insights about the membrane proton conductivity mechanism are given.
© 2010 The Electrochemical Society. DOI: 10.1149/1.3439671 All rights reserved.
Manuscript submitted February 4, 2010; revised manuscript received May 6, 2010. Published June 11, 2010. This was Paper 879
presented at the Vienna, Austria, Meeting of the Society, October 4–9, 2009.
Polymer electrolyte membrane fuel cells PEMFCs are very at-
tractive as energy efficient and environmentally friendly power
sources for many applications including transportation, distributed
power, and portable power systems. However, important scientific,
technical, and economical problems need to be solved before
PEMFC commercialization is possible. Two of the main issues fac-
ing the development of commercial low temperature fuel cells are
the synthesis of efficient solid electrolytes separating the anode from
the cathode and the development of cheaper catalysts for fuel oxi-
dation. Hydrated perfluorosulfonic acid membranes, such as Nafion,
are typically used as electrolyte in fuel cells because they combine
good mechanical properties and thermal stability with relatively
high electric conductivity under high humidity conditions.
1,2
Never-
theless, the major drawbacks in perfluorosulfonic acid membranes
are the high cost of the base material and the fact that these mem-
branes are prone to rapid dehydration at elevated temperatures. Un-
der fuel cell operating conditions, the decrease in the humidification
of the membranes caused by water evaporation and electro-osmotic
processes results in the loss of conductivity and, in some cases, in
irreversible changes in the membrane’s microstructure, despite the
fact that the membrane dryness caused by the combined effect of
these two processes may be somewhat alleviated by the back-
diffusion of the water produced at the cathode.
In this context, the synthesis of new composite ion-exchange
materials that could be used as a solid electrolyte with high proton
conductivity plays a fundamental role in the development of new
PEMFCs.
3-9
The investigation of their functional properties is a new
thriving research area in membrane electrochemistry, where such
composites are applied, e.g., as separation membranes in electrodi-
alysis.
Recently, research interest has been focused on Nafion mem-
branes modified by conducting polymers such as polyaniline PAni
due to its unique electrical and electrochemical properties.
7,8,10
In
our earlier studies,
11-13
we prepared and characterized nanocompos-
ite membranes modified by PAni and investigated their conductivity,
permselectivity and electrotransport phenomena, and morphology.
The obtained results showed that the nanocomposite membranes of
the PAni/MF-4SC type could have interesting transport properties as
solid electrolytes for fuel cell applications.
In this work, we report on the conductivity measurements of
membrane electrode assemblies MEAs prepared from PAni/MF-
4SC composite membranes. The membranes used in this study are
perfluorinated sulfocationic membranes of MF-4SC type Plastpoly-
mer, Russia
12
with such special properties as high thermal and
chemical stability along with good conductivity. Fuel cell perfor-
mance of MEAs is also investigated by measuring their polarization
curves in different operating conditions. We discuss the observed
differences in the membrane’s performance, paying special attention
to how the protocol used for the membrane ohmic resistance mea-
surement affects the proton conductivity values. The MEAs’ conduc-
tivity under operating conditions at different temperatures is fitted to
a one-dimensional isothermal steady-state model
14
showing good
agreement for low current densities, from where we infer some in-
sights about the proton conduction mechanism in the membrane.
Experimental
Materials.— A perfluorinated sulfocationic membrane MF-4SC
Nafion type produced by “Plastpolymer” St.-Petersburg, Russia
was used as a template matrix for the preparation of composites.
12
These composites are considered to be the result of PAni intercala-
tion into the initial unmodified membrane. Figure 1 shows the
chemical structure of both the template matrix that is, the perflu-
orinated sulfocationic membrane and the PAni in the emeraldine
form. Before the composite preparation, the MF-4SC membrane was
treated by oxidative-thermal conditions. This technique includes the
successive boiling of the films: first in 5% HNO
3
recovers the trans-
parency of the membranes and converts them into H
+
form, then in
10% H
2
O
2
oxidizes the remaining products in the membranes, and
finally in distilled water. In each solution the boiling lasted for 3 h.
After this procedure, MF-4SC membrane proton conductivity be-
came close to that reported for Nafion 117.
15
The composite templates were chemically synthesized according
to Ref. 16. Two different synthesis versions were implemented. In
version 1, the polymerization was carried out in a glass by the con-
tact method. The membrane was saturated in a solution of
0.01 M aniline An + 0.5 M HSO for 24 h in static condition.
After this, the sample was washed with water and placed in a solu-
tion of 0.01 M FeCl
3
in 0.5 M H
2
SO
4
initiator of the polymeriza-
* Electrochemical Society Active Member.
z
E-mail: vicommo@ter.upv.es
Journal of The Electrochemical Society, 157 8 B1186-B1194 2010
0013-4651/2010/1578/B1186/9/$28.00 © The Electrochemical Society
B1186
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