Design of sulfonated polystyrene grafted cellulose acetate membrane for direct methanol fuel cells

Abstract

Novel low-temperature proton conducting membranes are fabricated from commercial and low-cost cellulose acetate (CA). Rather than a normal modification procedure, sodium 4-styrene sulfonate groups (SSA) are grafted into cellulose acetate chains through a facile one-step free radical polymerization. The resulting CA@P(SSA) membranes with different monomer concentrations were characterized using advanced and relevant techniques such as FT-IR, TGA, and SEM. The grafting of side-chain groups was adjusted to maximise the physicochemical features of the fabricated membranes, such as ion exchange capacity, water and methanol absorption, and conductivity. By considering these features the optimized membrane (Corresponding to 1.5 wt% SSA) exhibits excellent thermal-oxidative stability and tensile strength (22.742 N) better than Nafion® 212 (16.153 N). In addition, the grafted membrane demonstrated lower methanol permeability (5.514×10−7cm2/s)andenhanced ionic conductivity (4.77×10−3S/cm) with membrane selectivity of 8.65×103S.s/cm3 with peak power density (24.6 mW/cm2). In addition, the optimized membrane showed increase in performance than pristine CA membrane. Thus, these results provide new, straightforward, high-performance and low-cost polyelectrolyte membrane with a significant potential for direct methanol fuel cell.