Development of cesium phosphotungstate salt and chitosan composite membrane for direct methanol fuel cells

A novel composite membrane has been developed by doping cesium phosphotungstate salt (CsxH3−xPW12O40 (0 ≤ x ≤3), Csx-PTA) into chitosan (CTS/Csx-PTA) for application in direct methanol fuel cells (DMFCs). Uniform distribution of Csx-PTA nanoparticles has been achieved in the chitosan matrix. The proton conductivity of the composite membrane is significantly affected by the Csx-PTA content in the composite membrane as well as the Cs substitution in PTA. The highest proton conductivity for the CTS/Csx-PTA membranes was obtained with x = 2 and Cs2-PTA content of 5 wt%. The value is 6 × 10−3 S cm−1 and 1.75 × 10−2 S cm−1 at 298 K and 353 K, respectively. The methanol permeability of CTS/Cs2-PTA membrane is about 5.6 × 10−7, 90% lower than that of Nafion-212 membrane. The highest selectivity factor (φ) was obtained on CTS/Cs2-PTA-5 wt% composite membrane, 1.1 × 104/S cm−3 s. The present study indicates the promising potential of CTS/Csx-PTA composite membrane as alternative proton exchange membranes in direct methanol fuel cells.