Journal of Membrane Science 351 (2010) 58–64 Contents lists available at ScienceDirect Journal of Membrane Science journal homepage: www.elsevier.com/locate/memsci Enhanced transport performance of sulfonated mesoporous benzene-silica incorporated poly(ether ether ketone) composite membranes for fuel cell application Eun-Bum Cho, Dinh Xuan Luu, Dukjoon Kim ∗ Department of Chemical Engineering, Polymer Technology Institute, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746, Republic of Korea article info Article history: Received 5 November 2009 Received in revised form 29 December 2009 Accepted 13 January 2010 Available online 21 January 2010 Keywords: Fuel cell Membrane Mesoporous benzene-silica PEEK Proton conductivity abstract Sulfonated poly(ether ether ketone) (sPEEK)/mesoporous benzene-silica electrolyte composite mem- branes were prepared using a solvent casting method. The two components were mixed thoroughly in N,N-dimethyl acetamide, at various concentrations up to 20 wt% of the mesoporous benzene-silica powder. The degree of sulfonation was 65% for sPEEK, and the ion-exchange capacity of mesoporous benzene-silica was 0.60 mequiv./g. The mesoporous benzene-silica material had a 2D hexagonal (p6mm) mesostructure with a pore diameter of 2.7 nm. The composite membranes exhibited higher proton conductivities than a pristine sPEEK membrane, and the proton conductivity increased with temper- ature. However, the sPEEK-based composite membranes showed very low methanol crossover below 5 × 10 -7 cm 2 /s, but this value was still in the same range as the pristine sPEEK membrane. A maximum proton conductivity of 0.079 S/cm was obtained for the sPEEK-OMB15 membrane at 80 ◦ C, and the highest DMFC cell performance was at 56 mW/cm 2 , which were approximately 119 and 37% increases compared to the pristine sPEEK membrane, respectively. © 2010 Elsevier B.V. All rights reserved. 1. Introduction During the last 20 years, proton exchange membrane fuel cells (PEMFCs) have been explored as new power sources for portable devices and automobiles. The development of an efficient polymer electrolyte membrane is a key technology for the improvement of high performance fuel cells [1–3]. Although the commercial Nafion ® membrane demonstrates a high proton conductivity, good processability, and high mechanical and chemical stability, it is still plagued by a few disadvantages, such as high fuel (methanol) crossover and high production cost because of the fluorine-based polymerization [4–9]. Therefore, the development of alternative fluorine-free polymer electrolyte membranes has been an impor- tant research topic in order to resolve the inherent material and economical problems. A variety of hydrocarbon-based polymers and their copolymers have been exploited, such as polystyrene, poly(arylene ether), poly(ether ether ketone), polybenzimidazole, and polyimide, in order to find alternatives to Nafion ® [10–20]. Fur- thermore, advanced processing conditions and various inorganic fillers have been introduced to enhance the transport properties and the stability of the membranes [20–29]. ∗ Corresponding author. Tel.: +82 31 290 7250; fax: +82 31 299 4700. E-mail address: djkim@skku.edu (D. Kim). A specific polymer membrane must meet several basic require- ments to be used both as an electrolyte and a separator for a PEMFC under real operating conditions: (i) mechanical and dimensional stability so that the membrane does not swell in a hydrated state; (ii) retention of water to maintain a high conductivity; (iii) oxida- tive stability of the polymer chains. Generally, the aforementioned aromatic backboned polymers have excellent thermal stability, mechanical strength, and oxidation stability. However, a high sul- fonation degree (SD) causes the polymers to swell more (leading to fuel crossover) and to mechanically weaken. In an effort to over- come the natural drawbacks of organic polymers, organic/inorganic hybrid polymer membranes with various functionalized silica and organosilica precursors have been investigated, and recently, porous materials, such as zeolite and functionalized mesoporous silica materials, have been used to prepare more efficient elec- trolyte membranes [23,30–35]. Mesoporous silica-based materials have extensively been devel- oped for a variety of applications because of their high surface area, narrow pore size distribution, and adjustable mesopore size in the range of 2–10 nm [36]. During the past decade, a new class of hybrid mesoporous silica, known periodic mesoporous organosil- icas (PMOs), was developed to synthesize organically modified mesoporous particles with altered properties [37–39]. The PMO materials are attractive because of their homogeneous distribution and high loading of organic groups inside the pore channel wall, cre- ating uniformity with the organic moieties inside the framework of 0376-7388/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2010.01.028