Preparation And Characterization Of Novel Organic-inorganic Composite Membranes For Directmethanol Fuel Cells

Direct methanol fuel cell, use methanol solution as the fuel supply avoid the drawbacks of hydrogen in the hydrogen- oxygen fuel cell that difficult to store, transport and unsafe. And due to its simple structure, abundant sources, quick start at low temperature and can use the existing refueling system, which has captured the attention of many researchers in recent years. Proton exchange membrane,which is one of the key components of direct methanol fuel cell, has bifunctional effects of proton transfer and the barrier between fuel and oxidant. Excellent proton exchange membrane must possess good proton conductivity, high methanol resistance and good mechanical prosperities. However, perfluorinated ionomer Nafion® of DuPont Company,which is uccessful used as electrolyte membranes in in hydrogen- oxygen fuel cell, has some drawbacks of high methanol permeability and high cost in DMFC. Therefore, development of novel proton exchange membrane with low methanol permeability and cost is very necessary.First, water absorbed silica coating on CNTs was successfully achieved via sol-gel process to fabricate SiO2 @ CNTs hybrid material. Then, novel SPEEK / SiO2 @ CNTs organic/inorganic composite membranes were prepared by doping SiO2 @ CNTs in SPEEK matrix. The formation of SiO2 shell can effectively shield the CNTs electronic conduction and enhanced its dispersion in the polymer matrix, meanwhile provide a hygroscopic capacity surface. The result showed that the composite membrane had higher methanol resistance and excellent thermal stability compare to pure SPEEK membranes. And the composite membrane still exhibited adequate conductivity above 10-2 S·cm-1 that satisfied the requirements in DMFC for application as proton exchange membranes.Second, noval Chitosan/ CaCO3 nanofluids composite membrane was prepared use good film-forming and natural polymer material chitosan(CS) as matrix, liquid like at room temperature hybrid material solvent-free CaCO3 nanofluids as addition. On the one hand, the plasticizing and enhance effect of CaCO3 nanofluids improved the flexibility and mechanical properties of the chitosan matrix, and the thermal stability of the composite membrane was improved; On the other hand, the addition of CaCO3 nanofluids increased the proton conductive path, thus improved the proton conductivity of the membrane.Third, noval CS/SiO2 @ CNTs composite proton exchange membrane was prepared use SiO2 @ CNTs as strengthen filter. High hygroscopicity SiO2 coating effectively improved the dispersion of CNTs in chitosan matrix. Thermal stability, oxidation resistance and tensile strength of the composite membrane increased significantly, meanwhile improved the conductivity and methanol resistance to some extent.