| Proton exchange membrane fuel cells(PEMFCs)is a power generation device which generates electricity directly through the electrochemical reaction of fuel and oxidant.PEMFCs does not burn violently,so it has the advantages of stable operation and low emission of pollutants.It is recognized as one of the best power generation devices converted from chemical energy to electric energy efficiency.Proton exchange membrane(PEM)is the core component of PEMFCs.Its main function is to transfer anode protons to the cathode and prevent fuel cross.The DuPont Nafion is the most widely used membrane.It has a stable C-F main chain,the branch chain contains-SO3H,the main chain and the branch chain links by oxygen,proton conduction mainly by the proton of-SO3H and H2O combined with the formation of hydrous protons.Therefore,the good conductivity of Nafion membrane must depend on water,when the fuel cell working temperature is higher than 80?,resulting in its low electrochemical activity.Ionic liquids(IL)have the advantages of non-volatile,high conductivity at high temperature and high thermal stability.They are ideal middle temperature and anhydrous conductive membrane materials.According to the literature,conductivity of IL is related to its structure.The IL with imidazole structure,structure stable,and two potential point N can increase the number of hopping sites.The distance between two N in imidazole is similar to the H in H2O,and its pKa value is similar to water,so imidazole IL becomes a good electrolyte for medium temperature and anhydrous.However,IL is a liquid substance that can not be stable in the membrane.However,IL is a liquid substance which can not be stable in the membrane,and requires stable solid media such as SiO2 to carry it.In order to improve the flexibility and mechanical properties of membranes,sulfonated poly(ether ether ketone)(SPEEK)was introduced.Sulfonated hollow mesoporous organosilica(sHMO)were prepared by functionalization of hollow mesoporous organosilica(HMO),and their proton conductivity was increased.Because HMO has a larger specific pore volume and a large amount of hydroxyl groups on the surface,it has a greater contribution to the retention of IL.In the SPEEK,1-butyl-3-methylimidazolium tetrafluoroborate([BMIm][BF4])was doped,the SP/IL/sHMO-x composite membrane was prepared for the first time,and the properties of the composite membrane were studied.The results are as follows:1)HMO was synthesized and sulfated successfully.2)the light yellow,transparent and homogeneous SP/IL,SP/IL/HMO-x and SP/IL/sHMO-x(x=2.5,5,7.5 and 10 wt%)composite membranes were prepared by the casting process,with a thickness of about 0.15-0.3 nm.3)FT-IR results showed that no new chemical bonds were formed between SPEEK,IL and organosilica,and the components were combined by intermolecular hydrogen bonding.4)the TG results showed that the propylsulfonic acid group in sHMO could be stable before 350?,and all the membrane could be stable before 240?.5)the results of IL loss showed that the more organosilica content,the more helpful to retention IL,while the sHMO composite membrane had poorer IL retention capacity than HMO.6)the conductivity results show that the sulfonation of organosilica has a certain contribution to the conductivity of the composite membrane.When sHMO is 7.5 wt%,the conductivity of SP/IL/sHMO-7.5 reaches 1.13 mS/cm,which is twice the conductivity of the SP/IL/sHMO-7.5. |
PDF Full Text Request