Journal of Power Sources 162 (2006) 1–8
Preparation and properties of sulfonated poly(ether ether ketone)s
(SPEEK)/polypyrrole composite membranes for
direct methanol fuel cells
Xianfeng Li
a
, Changpeng Liu
b
, Dan Xu
a
, Chengji Zhao
a
, Zhe Wang
a
,
Gang Zhang
a
, Hui Na
a,∗
, Wei Xing
b
a
Alan G. MacDiarmid Institute, College of Chemistry, Jilin University, Changchun 130012, PR China
b
Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China
Received 26 April 2006; received in revised form 9 June 2006; accepted 9 June 2006
Available online 25 July 2006
Abstract
Polypyrrole (Ppy) was successfully introduced into methyl substituted sulfonated poly(ether ether ketone) (SPEEK) membranes by poly-
merization in SPEEK solutions to improve their methanol resistance. Uniform polypyrrole (Ppy) distributed composite membranes were
formed by this method by the interaction between SPEEK and Ppy. The properties of the composite membranes were characterized in detail.
The composite membranes show very good proton conductive capability (25
◦
C: 0.05–0.06 s cm
−1
) and good methanol resistance (25
◦
C:
5.3 × 10
−7
–1.1 × 10
−6
cm
2
s
−1
).The methanol diffusion coefficients of composite membranes are much lower than that of pure SPEEK mem-
branes (1.5 × 10
−6
cm
2
s
−1
). The composite membranes show very good potential usage in direct methanol fuel cells (DMFCs).
© 2006 Elsevier B.V. All rights reserved.
Keywords: SPEEK; Ppy; DMFC; Proton exchange membranes
1. Introduction
The direct methanol fuel cell (DMFC) is a type of fuel cell,
which is potentially suitable for applications in automobiles
(cars, trucks and buses) or portable applications (cell phones
and laptops) because of its simple fueling (easy storage of
methanol, no reformer required), low emissions and low oper-
ating temperatures [1,2]. Some applications for DMFCs also
include distributed power for both stationary and dynamic appli-
cations where they could replace batteries. Each application
shares a common goal of high fuel efficiency, non-polluting
by-products and economical proton exchange membranes. The
proton exchange membrane material is a key component of the
PEMFC for transferring protons from the anode to the cathode
as well as providing a barrier to fuel crossover between the elec-
trodes. The membranes traditionally used in a proton exchange
membrane fuel cell (PEMFC) are perfluorosulfonic polymers,
∗
Corresponding author. Tel.: +86 431 5168870; fax: +86 431 5168868.
E-mail address: huina@jlu.edu.cn (H. Na).
such as Nafion
®
. Although they show superior performance in
fuel cells, their high cost and high methanol crossover make
them impractical for large-scale production [3,4]. Therefore,
alternative membrane materials such as sulfonated poly(aryl
ether ketone)s (SPAEK) [5], sulfonated poly(aryl ether sul-
fone)s (SPAES) [6] and sulfonated poly(imide) (SPI) [7], etc.
are being widely studied. In our previous work, SPAEK was
developed for proton exchange membranes [8–10]. Although it
showed relatively good properties for fuel cells, the brittleness of
the membranes at elevated temperatures and the relatively high
methanol permeability in the membranes with high sulfonation
have limited their usage. For the DMFC, a high methanol per-
meability rate across the proton exchange membranes poses a
critical problem in reducing the practical use of a DMFC. There
have been many attempts to reduce the methanol permeability
through the proton exchange membranes, which are: (1) modify
the membranes’ surface to block methanol transport, (2) control
the size of the transport channels of protons, (3) explore new
types of membrane materials, etc. Recently developed acid–base
composite membranes were widely used to solve this prob-
lem. Especially the blend of sulfonated polymers with polymers
0378-7753/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jpowsour.2006.06.030