Glutaraldehyde cross-linked sulphonated poly styrene ethylene butylene poly styrene membranes for methanol fuel cells

New, cheap proton conducting crosslinked membranes based on sulphonated poly styrene ethylene butylene poly styrene (SPSEBS) and glutaraldehyde (2 to 10 %) were synthesized as substitute for costly Nafion117 membrane. Glutaraldehyde was used as the cross-linking agent in order to improve dimensional stability. The proton conductivity of the crosslinked membranes was in the order of 10⁻²S/cm at 25 °C. Proton exchange membrane fuel cell achieved the maximum power density of 68 and 58 mW/cm², at a current density of 200 mA/ cm²for cross-linked membranes with glutaraldehyde content 2 and 10 % respectively. The methanol permeability of the cross-linked membrane (in the range of 16.22 to 11. 89 × 10⁻⁷ cm²/s) was much lower than that of Nafion 117 (35.2 × 10⁻⁷ cm²/s). Direct methanol fuel cell (2 M concentration at 25 °C) consisting of cross-linked membrane was assembled and systematically examined. The crosslinked membranes containing 2 and 10 % glutaraldehyde showed maximum power density of 56 and 67.5 mW/cm², respectively. The performance of cross-linked membranes in both the cells was several times higher than that of Nafion 117. Hence the cross-linked membrane is a viable substitute for Nafion 117 for fuel cells applications. In this study the formation of sulphonated PSEBS and cross-linked structure was ascertained through FTIR and X-ray diffraction spectra, scanning electron microscopy and thermal analysis.