Preparation and characterization of polyvinyl alcohol/chitosan blended membrane for alkaline direct methanol fuel cells Jen Ming Yang n , Hsien Chih Chiu Department of Chemical and Materials Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan article info Article history: Received 5 May 2012 Received in revised form 16 June 2012 Accepted 30 June 2012 Available online 7 July 2012 Keywords: Polyvinyl alcohol Chitosan Ionic conductivity Methanol permeability Alkaline direct methanol fuel cells abstract A novel polyvinyl alcohol/chitosan, PCS, blended membrane is prepared by direct blend process and solution casting method. In order to reduce the swelling ratio and enhance the chemical and thermal stabilities of the PCS, PCS membrane is crosslinked with glutaraldehyde to get PCS-G membrane. These membranes are characterized by differential scanning calorimetry, X-ray diffraction, thermogravimetry analysis and mechanical properties of tensile strength and elongation at breaking. The structures of these membranes are identified with azocarmine G. The various membranes are immersed in KOH (aq) solution to form polymer electrolyte membranes and then the alkaline uptake and swelling ratio in the thickness (SW L ) and plane direction (SW A ) in membranes are studied. The ionic conductivity and methanol permeability of the membranes are conducted. It is found that the value of methanol permeability through the membrane is lower than that of Nafion membrane. Compared to data of Nafion and other studies, PCS91-G membranes with higher selectivity suggest their potential applications in DMFC. & 2012 Elsevier B.V. All rights reserved. 1. Introduction As the wide potential applications in electrochemical devices, such as batteries and supercapacitors, alkaline solid polymer electrolyte (ASPE) has been considerably investigated [1–14]. Fauvarque et al. have reported studies about alkaline solid polymer hydrogel electrolytes based on poly(ethylene oxide) for application on Ni–Cd, Ni–Zn, and Ni–MH secondary battery systems [1,2]. The ionic conductivity of alkaline poly(ethylene oxide)-based polymer electrolytes was further reported around 10 3 S cm 1 at room temperature [1,2]. Iwakura et al. prepared polymer hydrogel electrolyte with high conductivity from acrylic acid and KOH (aq) solution [15]. The semi-crystalline polyvinyl alcohol, PVA, is also an attractive material for the use as a polymer hydrogel electrolyte. Series results about the preparation and characterization of PVA-based polymer electrolytes and applica- tion for Zn–air batteries, rechargeable Ni–MH batteries and direct methanol fuel cell [3–11,16–28] have been reported. Chitosan (CS), [poly-b(1–4)-D-glucosamine], a cationic poly- saccharide, is obtained by alkaline deacetylation of chitin, the principal exoskeletal component in crustaceans. As the combina- tion of properties of chitosan such as water binding capacity, fat binding capacity, bioactivity, biodegradability, nontoxicity, bio- compatibility, and antifungal activity, chitosan and its modified analogs have shown many applications [29–36]. As chitosan membranes have been found to have excellent film-forming properties and high mechanical strength, they are suitable for haemodialysis [37,38], ultrafiltration, reverse osmosis, pervapora- tion and fuel cells [39–41]. Blending of chitosan with PVA or quaternized chitosan with quaternized polyvinyl alcohol (QAPVA) had been reported to improve mechanical stability and the evaluation of methanol permeability and proton conductivity [28,42]; whereas the elec- trochemical performance for the direct methanol fuel cell was not reported. In alkaline DMFCs, it is critical to both overcome methanol permeability and enhance ionic conductivity. Numer- ous researchers have utilized different polymers in the synthesis of alkaline ion-exchange membranes; consequently, the mechan- ical and electrochemical properties of ion-exchange membranes have been significantly improved. Various alkaline membrane ionic conductivities are shown in Table S1. In this study PVA modified by chitosan to get modified PCS membrane and their performances for alkaline direct methanol fuel cell are reported. The homogeneous, nonporous PCS membranes were prepared by casting the polymer solutions with different PVA/ CS ratio and drying at room temperature at least 24 h. In order to improve the stability of PCS membrane in KOH (aq) solution, PCS membrane was crosslinked with glutaraldehyde to get PCS-G membrane. The structures of these membranes are identified with Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/memsci Journal of Membrane Science 0376-7388/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.memsci.2012.06.051 n Corresponding author. Tel.: þ886 3 2118800; fax: þ886 3 3274901. E-mail addresses: jmyang@mail.cgu.edu.tw, yangjenming@yahoo.com.tw (J. Ming Yang). Journal of Membrane Science 419–420 (2012) 65–71