Synthesis Of Poly (Aryl Ether Ketone) Polymers Modified With Polyoxometalates And Their Applications In Proton Exchange Membranes

Proton exchange membrane fuel cells is an environment-friendly energy device which meets the needs of current energy problems.It has high energy conversion efficiency and is suitable for a variety of applications.Sulfonated poly（aryl ether ketone）is expected to become a more economical and affordable alternative to Nafion membrane due to its low cost,convenient preparation and high proton conductivity.However,for sulfonated poly（aryl ether ketone）,high proton conductivity often requires high sulfonation degree of the polymer itself.High sulfonation degree will lead to the decrease of tensile strength,poor oxidation stability,excessive swelling and even dissolution of sulfonated poly（aryl ether ketone）.Therefore,in order to meet the application requirements of proton exchange membrane fuel cells,sulfonated poly（aryl ether ketone）needs not only low sulfonation degree,but also excellent proton conduct ability.Organic-inorganic blending modification is a modification method with simple process,strong designability,rich available composites,wide sources and easy availability.At present,many research results have proved that the water holding capacity and proton conductivity of composite membranes can be improved by introducing functional inorganic materials into polymer matrix.In resent years,polyoxometalates,as a new type of proton conductor,have attracted extensive attention.polyoxometalates is a kind of crystal material with oxygen enriched surface.The characteristics of oxygen enrichment on its surface are often conducive to the construction of richer hydrogen bond networks,which is conducive to proton conduction.Based on the functional characteristics of polyoxometalates,polyoxometalates was introduced into sulfonated poly（aryl ether ketone）as inorganic functional material for doping modification.polyoxometalates as surface oxygen enriched crystal material produced more hydrogen bonds in the hybrid film;As a Br?nsted acid,it provides protons as a proton source in the process of proton conduction;On this basis,the host guest interaction solves the dissolution problem of polyoxometalates,further improves the proton conductivity and mechanical strength of the hybrid membranes,and reduces the dissolution rate of polyoxometalates in water;The work of this paper is as follows:（1）Firstly,the positively charged bismuth oxygen cluster H₆Bi₁₂O₁₆ on the surface is selected to characterize the structure and cross-sectional morphology of sulfonated poly（aryl ether ketone sulfone）with low sulfonation degree under different doping amounts of bismuth oxygen clusters,and its mechanical strength,proton conductivity and methanol permeability are measured at the same time.The results show that H₆Bi₁₂O₁₆ hybrid membranes has the highest conductivity(72.8 m S·cm^-1 at 80oC)and tensile strength（43.57 MPa）at 5 wt%doping.At the same time,it is compared with sulfonated poly（aryl ether ketone sulfone）pure membrane at 30%sulfonation degree under the same test conditions.It is proved that the introduction of polyoxometalates can contribute to the conductivity of sulfonated poly（aryl ether ketone sulfone）and the contribution to conductivity shows that it can replace sulfonate to a certain extent.（2）Giant polyoxomolybdates with imidazole ligands have been proved to have good proton conductivity.On the one hand,the surface of HIm{Mo₁₃₂}is rich in oxygen and the structure is rich in carboxyl and imidazole,which can build a richer hydrogen bond network with the sulfonic acid group on the main chain of the polymer;On the other hand,the pore structure of HIm{Mo₁₃₂}provides an additional transport channel for the free entry and exit of carrier protons in the hybrid membrane,which further improves the proton conduction performance of the hybrid membrane.Among them,when the doping amount of HIm{Mo₁₃₂}reaches 10 wt%,the hybrid membrane has the best and highest conductivity(59.6 m S·cm^-1at 80oC).It is proved that the introduction of giant polyoxomolybdates clusters helps to improve the proton conductivity of sulfonated（poly aryl ether ketone sulfone）.