Abstract:

Sulfonated poly（pathalazinone ether ketone）（SPPEK）is an alternative membrane material for direct methanol fuel cells because of its reasonable conductivity and methanol resistance. However，its conductivity depends much on the water content. At a temperature higher than 100℃，the conductivity of SPPEK membrane drops sharply due to the evaporation of water. The present paper focuses on improving the water holding ability of SPPEK membrane by embedding a hygroscopic proton conductor. Zirconium tricarboxybutyl phosphonate［Zr（PBTC）］was chosen as the hygroscopic additive for its relatively high conductivity. Zr（PBTC）/SPPEK composite membrane was obtained by casting a homogeneous mixture of Zr（PBTC）and SPPEK in N，N-dimethylacetamide onto glass plate and then evaporating the solvent at 60℃. The conductivity of membranes at different relative humidities at 120℃ and the water content at different temperatures were measured. The results showed that incorporating Zr（PBTC）improved the water holding capacity of composite membranes at a low humidity，thereby improving their conductivity. At 120℃，when relative humidity varied from 100% to 20%，the conductivity of SPPEK membrane dropped sharply from 10^-1 S·cm^-1 to 10^-5 S·cm^-1 while that of 30%（mass） Zr（PBTC）/SPPEK composite membrane dropped to 10^-3 S·cm^-1.