DMFC用PES/SPEEK共混阻醇质子交换膜

将磺化聚醚醚酮(SPEEK, 磺化度DS为68.3%)和聚醚砜(PES)两种聚合物共混制得PES/SPEEK共混膜. DSC研究表明两种聚合物之间具有较好的相容性, 因而共混膜均匀致密, 未发生大尺度相分离. PES的混入能有效降低膜的溶胀度及甲醇透过系数. 纯SPEEK 膜40 ℃时在1 mol•L−1甲醇水溶液中溶胀度达到160%, 45 ℃时就完全溶解, 而含30%(w)PES的共混膜在80 ℃时的溶胀度仅有15%. 室温下含20%−30%(w)PES的共混膜的甲醇透过系数为1×10−7 cm2•s−1左右, 比Nafion 115膜的透过系数小一个数量级. 尽管80 ℃下30%(w)PES/SPEEK共混膜的电导率与Nafion 115膜相当, 但由于共混膜的厚度比Nafion 115膜小1/3左右, 膜电阻较小, 因而其电池性能比Nafion 115膜的好.

Methanol Resistant Poly(Ether Sulfone)/Sulfonated Poly(Ether Ether Ketone) Blend Proton Exchange Membrane for DMFC

Sulfonated poly(ether ether ketone) (SPEEK) is a very promising alternative membrane material for direct methanol fuel cells. However, with fairly high degree of sulfonation (DS), which enables high proton conductivity, SPEEK membranes can excessively swell or even dissolve. To deal with this contradictory, poly(ether sulfone) (PES) was blended into SPEEK to prepare PES/SPEEK blend membranes by solvent evaporating. Characteristics of the blend membranes, including thermal property, swelling degree, methanol permeability, proton conductivity and single cell performance, were investigated. DSC results reveal that the two polymers show good miscibility, which results in the homogeneity of the blend membranes. Methanol permeability and swelling degree of the blend membranes are both improved efficiently. The membranes with 20%−30%(w) of PES present the methanol permeability in the order of 1×10−7 cm2•s−1, which is an order of magnitude lower than that of Nafion 115. High proton conductivity of the blend membranes can also be achieved because of increased applicable temperature of membranes. Under 100% relative humidity, the conductivity of blend membrane with 30%(w) PES shows to be 0.078 S•cm−1 at 80 ℃. The single cell performance of blend membrane with 30%(w) PES is better than that of Nafion 115 membrane for its reduced thickness and thereby the resistance.