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 (Cs_xH_3-xPW₁₂O ₄₀ (0 ≤ x ≤3), Cs_x-PTA) into chitosan (CTS/Cs _x-PTA) for application in direct methanol fuel cells (DMFCs). Uniform distribution of Cs_x-PTA nanoparticles has been achieved in the chitosan matrix. The proton conductivity of the composite membrane is significantly affected by the Cs_x-PTA content in the composite membrane as well as the Cs substitution in PTA. The highest proton conductivity for the CTS/Cs_x-PTA membranes was obtained with x = 2 and Cs ₂-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/Cs_x-PTA composite membrane as alternative proton exchange membranes in direct methanol fuel cells.