Study On Nanofibers Containing Porous Organic Cages And Their Modified Proton Exchange Membranes

The proton exchange membrane（PEM）is the core component of the proton exchange membrane fuel cell（PEMFC）.It can isolate fuel interactions and selectively and rapidly migrate and transport protons and its properties are critical to the performances of PEMFC.At present,commercial proton exchange membranes Nafion have poor conductivity at high temperatures,poor concentration diffusion of methanol and water,low selectivity for electron migration,and high production costs.Therefore,the development of high-performance proton exchange membranes has become a research hotspot.The use of proton-conducting nanofibers to construct long-range ordered proton transfer channels can strengthen the proton transfer process and enhance the mechanical properties of the membrane.The method of constructing high-performance proton exchange membranes has attracted widespread interest from researchers.Porous organic cages（POCs）are a kind of soluble three-dimensional porous organic materials emerging in recent years,showing their potential as proton conducting materials.In this paper,POC-containing nanofibers and their hybrid PEMs were prepared using in-situ growth and blend spinning methods.The specific contents include:The porous organic cage CC3 molecules were immobilized on the surface of PAN nanofibers by in-situ growth method,and then the hybrid proton exchange membrane was prepared by impregnation with Nafion membrane solution.The results of structure and performance studies show that CC3 can be immobilized by stepwise reaction Loaded on the surface of PAN nanofibers,the surface of CC3/PAN nanofibers is rough,the average diameter increases by about 50nm,and the specific surface area reaches113.6 m²/g;Introduction of CC3/PAN nanofibers significantly improved the thermal stability and water absorption of the composite membrane,and the swelling ratio of the composite membrane decreased significantly.By changing the proportion of CC3/PAN in the composite membrane,the barrier effect of the composite membrane on methanol is enhanced,and the effect is enhanced as the mass ratio increases.The in-situ synthesis method was used to form the CC3 layer on the surface of PAN nanofibers,providing more proton transfer sites,and successfully constructing long-range continuous proton transport channels to improve proton conductivity.The CC3/PAN-Nafion composite membrane has a proton conductivity of 0.16 S·cm^-1 at 80°C and 100%RH.The CC3 crystals were dissolved and blended with sulfonated polyethersulfone（SPES）to obtain hybrid nanofibers.PEMs with different CC3 contents were prepared after being impregnated with Nafion.The prepared hybrid nanofibers have good morphology,and the average diameter increases first and then decreases with the increase of CC3content,and the minimum diameter is 236 nm.With the increase of CC3 content,the thermal stability of the composite membrane increased,the water absorption rate increased significantly,and the water absorption rate at 80°C reached 48%.The hydrogen bonding interaction between the sulfonate and the amino group was found by infrared spectroscopy testing.Under the synergy of CC3@SPES nanofibers and Nafion,the proton conductivity of SCN-5.7 membrane can reach 0.315 S·cm^-1 at 80°C and 100%RH,and the barrier methanol performance is also an order of magnitude higher than that of SCN-0.The results of the single cell performance test of the SCN-5.7 membrane showed that the power density was much higher than that of the Nafion membrane.