Malaysian Polymer Journal (MPJ), Vol 2, No. 1, p 10 -28, 2007 10 Physico-Chemical Study of Sulfonated Poly(Ether Ether Ketone) Membranes for Direct Methanol Fuel Cell Application M. H. D. Othman, A. F. Ismail*, A. Mustafa Membrane Research Unit, Faculty of Chemical and Natural Resources Engineering, Universiti Teknologi Malaysia, Johor, Malaysia *Corresponding author: afauzi@utm.my ABSTRACT: Sulfonated poly(ether ether ketone) (SPEEK) membranes have been prepared as a potential polymer electrolyte membrane (PEM) for direct methanol fuel cell (DMFC) application. The SPEEK polymer was dissolved into N, N-dimethylacetamide (DMAc) in a subsequent step after sulfonating the raw polymer with concentrated sulfuric acid. The polymer solutions were then cast by pneumatic casting machine. The influence of sulfonation reaction temperature on ion exchange capacity (IEC) and degree of sulfonation (DS) have been investigated. The results showed that the IEC and DS are increased with the temperature. The resulting membranes were then characterized by evaluating their physico- chemical properties such as methanol permeability and proton conductivity as a function of DS. The overall results showed that sulfonation process successfully enhanced the proton conductivity of the membrane and the values were comparable with commercial membrane, Nafion ® 117, at room temperature. Although the methanol permeability of membrane also increased after sulfonation process and proportional with DS, the value was still lower than Nafion ® 117. Keywords: sulfonated poly(ether ether ketone), direct methanol fuel cell, methanol permeability, proton conductivity 1.0 INTRODUCTION Fuel cells have been gaining much attention as a promising alternative to replace conventional fossil fuel systems due to their high efficiency, low environmental impact and flexible application [1]. In fact, several types of fuel cells have been commercialized, such as proton exchange membrane fuel cell (PEMFC) which utilizes hydrogen as fuel [2]. PEMFC is interesting for automotive and portable applications because of its low operating temperature [3]. However, hydrogen is difficult to store, whether as a compressed gas, as a cryogenic liquid, or in metal hydrides or carbon nanotubes. As a result, effort has been made to utilize hydrogen produced from fuel like methanol, via steam reforming. This is then followed by hydrogen separation using a palladium alloy membrane to remove carbon monoxide. Such processing dramatically increases the weight and complexity of fuel cell system [4]. In order to simplify the system structure, direct methanol fuel cell (DMFC) using methanol as fuel is deemed as a potential option of energy converters, ascribable to the advantage of liquid methanol. In a DMFC, methanol is fed directly to the fuel cell without any fuel processing beforehand. The liquid-feed system does not require any fuel processing equipment and can even be operated at room temperature. These advantages lead to simplicity of operation in DMFC compared to systems using a reformer to produce hydrogen from liquid fuel (i.e. indirect methanol fuel cells) [1]. Therefore, bright prospect of DMFC can