Journal of Power Sources 172 (2007) 604–612 Sorbitol-plasticized chitosan/zeolite hybrid membrane for direct methanol fuel cell Weikang Yuan a , Hong Wu a , Bin Zheng a , Xiaohong Zheng a , Zhongyi Jiang a,∗ , Xiaopeng Hao b , Baoyi Wang b a School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, PR China b Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China Received 21 March 2007; received in revised form 12 May 2007; accepted 15 May 2007 Available online 18 May 2007 Abstract Organic–inorganic hybrid membranes, as promising direct methanol fuel cell membranes, have become a research focus in recent years. Wherein interfacial morphology, greatly influenced by the polymer chain flexibility and interfacial stress generated during membrane formation, is a critical determinant of efficient suppression of methanol crossover. In this study, a novel and feasible approach for rational fabrication of organic/inorganic hybrid direct methanol fuel cell (DMFC) membrane is tentatively explored. By adding plasticizer in the membrane casting solution and/or elevating solvent evaporation temperature during membrane fabrication, the glass transition temperature (T g ) and crystallinity of the chitosan/zeolite hybrid membrane are both remarkably decreased. In particular, the interface voids are substantially eliminated, generating a more desirable interfacial morphology and consequently leading to an improved performance in suppressing methanol crossover. The chitosan/mordenite/sorbitol hybrid membrane prepared with 30 wt% of sorbitol and 15 wt% of mordenite exhibits a 44% reduction in methanol permeability compared with chitosan control membrane. The variation of methanol permeability with mordenite and sorbital content is tentatively elucidated by the change of free volume cavity size in the membrane determined by positron annihilation lifetime spectroscopy (PALS) measurements. © 2007 Elsevier B.V. All rights reserved. Keywords: DMFC; Organic–inorganic hybrid membrane; Plasticizer; Interfacial morphology; Methanol crossover 1. Introduction Direct methanol fuel cell (DMFC), as an efficient and clean energy generator, provides an attractive alternative to the rechargeable battery in portable electronic devices [1]. Among the factors limiting the practical application of DMFC, methanol crossover through the polymer electrolyte membranes (PEMs), such as the most-commonly used Nafion membrane, constitutes one of the most concerned issues [2]. Synthesis of new types of polymer [3–7] and organic–inorganic hybrid materials [8–14] represent the prevailing strategies to reduce or inhibit methanol crossover in the development of DMFC-oriented membrane. Often referred to the next generation membrane [15–17], organic–inorganic hybrid membrane has attracted peculiar atten- ∗ Corresponding author. Tel.: +86 22 27892143; fax: +86 22 27892143. E-mail address: zhyjiang@tju.edu.cn (Z. Jiang). tion as a promising DMFC membrane alternative, due to the possibility of not only combining the favorable properties from both organic and inorganic worlds but also creating entirely new compositions with truly unique properties [18]. However, how to obtain a desirable interfacial morphology, which is a critical determinant of permeation performance, is an impor- tant research issue in organic–inorganic hybrid membrane realm [19]. The interfacial morphology of hybrid membranes is tightly associated with different preparation techniques. So far, two strategies for incorporating inorganic species into polymer matrix have been proposed: (i) in situ formation of inor- ganic particles within polymer matrix through sol–gel reaction [17,20–23] or crystallization [22]. It is claimed that the nano- sized inorganic particles and uniform dispersion can be achieved by this strategy and, in some cases, the covalent bonds formed between organic and inorganic components may allow delicate tailoring of the interfacial properties [23]. However, the diffi- 0378-7753/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2007.05.040