The Research Of Proton Exchange Inorganic-organic Hybrid Membrane Using GPTMS Chemically Bonded HEDP

Fuel cells utilizing proton exchange membranes (PEFCs) have the potential to become an important energy generation system for mobile, stationary and portable electrical devices because of their energy efficiency and clean exhaust gas. Since the Pt anode catalysts are easily poisoned by CO impurities in the fuel gas under low operation temperatures below100℃, it is necessary to improve the fuel cell operating temperature. However, the commercialized proton exchange membrane such as Nafion membrane, is easy to have water lost when the operation temperature is higher than100℃, leading to a sharp decline in proton conductivity. Therefore, it is necessary to develop a proton exchange membrane with high proton conductivity in low humidity and under the intermediate temperature. Among various alternative proton-conducting materials, the inorganic/organic hybrid is one of the promising materials for the proton-conducting membranesIn this paper, a serious of proton conductive inorganic-organic hybrid intermediate temperature membranes were prepared from3-glycidoxypropyltrimethoxysilane (GPTMS) and1-hydroxyethane-1,1-diphosphonic acid (HEDPA) by sol-gel process. The relationship between sol-gel temperature and the membrane performance was researched. FT-IR, TG-DSC and SEM results indicated that the degree of sol reaction is highest when the sol reaction temperature of50℃. As a membrane temperature of150℃, the flexibility of the membrane declined, but the film uniformity better, enhance the thermal stability of the membrane.The effection of different silicon-phosphorus ratios to membrane performance was discussed. The results of FT-IR, XRD, TG-DSC and hydrolysis resistance indicateed that the increasing of phosphonic acid content had a inhibitory impact on the formation of Si-O network. In additon, the reduction of phosphonic acid content is good at the generation of pseudo-polyether network, and help to enhance membrane flexible and hydrolysis resistance. Moreover, when the molar ratio of Si: P is6:1, the polymerization degree of the pseudo-polyether network and polysiloxane is the highest, and the obtained membrane has the best heat resistance and thermal stability.In order to prevent the leaching out of phosphonic acid, triethylamine was used as catalyst to promote the reaction of HEDPA and GPTMS to immobilize phosphonic acid groups. FT-IR spectra revealed that phosphonic acid groups of HEDPA were chemically bounded to organosiloxane network as a result of the reaction of P-OH of HEDPA and epoxy ring of GPTMS. TG-DSC results indicated that the hybrid membranes were thermally stable up to250℃. The proton conductivity of the hybrid membranes increased with temperature from30℃to130℃. The proton conductivity of hybrid membrane with the molar ratio of GPTMS/HEDPA=2/1can reach1.0x10-3S·cm-1under anhydrous condition at130℃, which reveals that this membrane is a promising proton exchange membrane for intermediate temperature proton exchange membrane fuel cell.