A class of phosphonic acid-grafted hybrid inorganicâorganic polymer membranes was synthesized using a solâgel process. Their thermal stability, water uptake, and proton conductivity were investigated. TGAâDSC analysis indicated that these membranes are thermally stable up to at least 220 °C in dry air. The proton conductivities of the new membranes increase with âPO3H2 group content and relative humidity, reaching 6.2 à 10â2 S cmâ1 at 100 °C with â¼100% relative humidity, comparable to those of Nafion® under similar conditions. These new membranes have high proton conductivity at low relative humidity and thus have great potential to be used as electrolytes for high-temperature, low-humidity PEM fuel cells and other electrochemical applications. The proton conductivity of the membranes in the anhydrous state was enhanced by substitution of âCH2âPO3H2 groups with âCF2âPO3H2 groups owing to the large electron-withdrawing effect of CâF bonds. However, it was found that the concentration of âPO3H2 groups and the molecular structures of the new membranes are the key factors for the proton transport process in a humidified environment.
采用溶胶法合成了一类膦酸接枝杂化无机聚合物膜。研究了这些膜的热稳定性、吸水性和质子传导性。TGAâDSC 分析表明,这些膜在干燥空气中的热稳定性至少可达 220 °C。新膜的质子传导率随âPO3H2基团含量和相对湿度的增加而增加,在100 °C、相对湿度为¼100%的条件下达到6.2 à 10â2 S cmâ1,与类似条件下的Nafion®膜相当。这些新膜在低相对湿度条件下具有高质子传导性,因此在高温、低湿度PEM燃料电池和其他电化学应用中用作电解质具有巨大潜力。由于CF2âPO3H2基团具有较大的电子吸收效应,因此用âCF2âPO3H2基团取代âCH2âPO3H2基团可提高膜在无水状态下的质子传导性。不过,研究发现,âPO3H2 基团的浓度和新膜的分子结构是质子在加湿环境中传输过程的关键因素。