Preparation And Properties Study Of Sulfonated Poly(Ether Ether Ketone)s Proton Exchange Composite Membranes

As the key component of the PEMFC, proton exchange membrane materials should provide excellent properties such as high proton conductivity, good chemical and mechanical stability. At present, due to the expensive price, high methanol diffusion and low proton conductivity at low humidity or high temperature, the traditionally used Du Pont Nafion membranes can not be widely applied in the commerce. Aromatic hydrocarbon polymers such as Sulfonated poly(ether ether ketone)(SPEEK) have been extensively studied due to their low cost and low methanol diffusion. However, the proton conductivity of the neat SPEEK is lower than the Nafion membranes because of the SPEEK structure itself. In order to improve the proton conductivity, we take the blend method to enhance the properties of the SPEEK membranes and the main work has been studied in chapter two.In chapter two, firstly, we synthesized the sulfonic acid functionalized ordered SBA-15 mesoporous silica with the Pluronic123 as surfactant. Here, we abbreviate the sulfonic acid functionalized ordered SBA-15 mesoporous silica with S-SBA-15. S-SBA-15 is a kind of good inorganic proton conductor which is hygroscopic and can provide high proton conductivity. Through the different reagent ratio, we synthesized two kinds of S-SBA-15 with different ion exchange capacities which were 1.4 mequiv.g-1 and 2.7 mequiv.g-1, respectively. Here, we denominate the two S-SBA-15 particles 1.4S-SBA-15 and 2.7S-SBA-15. FT-IR, XRD, SEM, TEM was used to characterize the structure and morphology of the two S-SBA-15 particles. The experiment result indicated that the 1.4S-SBA-15 with hexagonal 1D mesoscopic ordered structure and 1μaverage particle size was synthesized successfully, however, amorphous material with weaker mesoscopic order was obtained by 2.7S-SBA-15.In order to study the influence of S-SBA-15 inorganic particle on the composite membrane properties, different S-SBA-15 loading contents were incorporated into the neat SPEEK membranes through blend method using ultrasonic. The cross section of the composite membranes was characterized by SEM: when the loading content of fillers was proper, no obvious silica agglomeration occurred on the membrane cross-section, the sulfonated silica well dispersed in the membranes; the TGA and DTG indicated that the SPEEK/1.4S-SBA-15 composite membranes showed good thermal stability; mechanical tests showed that the mechanical stability was improved at some content. The composite membranes showed better water retention than neat SPEEK membrane because of the stronger interaction between 1.4S-SBA-15 and SPEEK. What is more important was that the proton conductivity of the composite membranes was improved greatly. Moreover, we found that the proton conductivity showed firstly increase and decrease afterward with the increase of the filler amount; the regular structure and mesoscopic order were also much more important factors for proton conductivity; the methanol diffusion coefficients of composite membranes were a little higher than the neat SPEEK membrane due to the large particle size and particle agglomeration.In chapter three, we prepared catalyst using glycol as reducing reagent, 1.4S-SBA-15 as a carrier of Pt nanoparticles. The structure of the Pt nanoparticles was characterized by XRD, SEM and TEM. We prepared Pt nanoparticles with the face-centred cubic structure and the average particle size was about 3nm. The catalysis of the 1.4S-SBA-15-Pt catalyst was approved by Cyclic voltammograms tests. In chapter two, we found that when the 1.4S-SBA-15 particle loading content was 5%, the properties of the composite membranes were best. So in this chapter, we choosed the 1.4S-SBA-15-Pt catalyst loading content as 5% to prepare the self-humidifying membrane SPEEK/1.4S-SBA-15-Pt by blend method in order to be applied in the H2/O2 fuel cell and studied some basic properties of the composite membrane. The composite membrane SPEEK/1.4S-SBA-15-Pt showed higher proton conductivity than neat SPEEK, but lower than SPEEK/1.4S-SBA-15. Compared with the self-humidifying membrane with normal SiO2-Pt catalyst as filler, I think the SPEEK/1.4S-SBA-15-Pt membrane had the better future.