Research Of Quaternized All-carbon-backbone Anion-exchange Membranes

As the energy crisis and environmental issues become more and more serious.Fuel cells,with zero environmental pollution,can efficiently convert chemical energy into electrical energy,which have attracted widespread attention.Alkaline anion exchange membrane fuel cells are a type of fuel cell.Compared with proton exchange membrane fuel cells,they have the characteristics of fast oxidation,low cost.However,the key component,anion exchange membranes still have many problems,such as low OH^- conductivity and poor alkaline stability,which restrict the commercialization of alkaline anion exchange membrane fuel cells.In this paper,three kinds of all-carbon-backbone anion exchange membranes are designed and synthesized.None of the membrane chemical structures contain alkali-sensitive aryl ether bonds,which makes the material exhibit good alkali stability.At the same time,by increasing the density of local functional groups,optimizing ion transmission channels and other methods to improve the membrane conductivity.In addition,the nitrile group can increase the intermolecular interaction,and the cross-linked structure can make the chain structure more compact,which can effectively suppress the membrane swelling and make the membrane show good dimensional stability.Firstly,Poly?styrene-co-acrylonitrile?is selected as the backbone,and functionalized them with trimethylamine to make the AS-TMAOH membranes.The introduced strong polar nitrile groups result in lower water uptake,excellent dimensional stability and strong alkali resistance of the AEMs.The swelling ratio of all membranes are kept below 15%.The AS-TMAOH-25 membrane with IEC of 1.2 mmol g^-1 exhibits the highest hydroxide conductivity of 35.25 mS cm^-1 at 70?.After immersed for 168 h in a 1 M KOH aqueous solution at 60? AS-TMAOH-25 membrane IEC and hydroxide conductivity are 84% and 80% of the initial values.Since the benzyl group is susceptible to degradation in alkaline environment,in order to further improve the alkaline stability of the membrane,a terminally functionalized piperazinium Poly?styrene-co-acrylamide?anion exchange membrane?PS-PMAA-PAOH?are prepared via amine transesterification and Menshutkin reaction.Because the structure doesn't contain alkali-sensitive aryl ether bonds and benzyl sites,and cyclic amines are used as conductive groups,the PS-PMAA-PAOH membrane exhibits excellent alkali stability.The PS-PMAA-PAOH-1.5 membrane immersed in 1 M NaOH at 60? After 168 h,the IEC retention rate is above 94%,the OH^-conductivity retention rate is above 92%.Moreover,Single cell testing using PS-PMAA-PAOH-1.5 showed an open circuit voltage of 1.00 V and a peak power density of 72.65 mW cm^-2 at 60?.Although polyolefin materials have good alkaline stability,compared to traditional aromatic polymers they have some inherent defects,such as poor mechanical properties.Therefore,an all-carbon aromatic polymer are synthesized by super acid catalyzed reaction through 1,4-dibromo-2,3-butanedione and biphenyl,and then through Menshutkin reaction for thermal cross-linking and functionalization to obtain the anion exchange membrane CL-PBDB-XOH,the structure increases the local functional group density for the dual-site functionalization,so that a better ion transmission channel is formed in the membrane,which makes it have high conductivity under low IEC conditions,The CL-PBDB-PIPOH-5membrane with IEC of 1.02 mmol g^-1 exhibits the highest hydroxide conductivity of 74.88 mS cm^-1 at 80?.In addition,there is no aryl ether bond and benzyl site in the structure to achieve high alkaline stability.The chemical structure of the CL-PBDB-XOH-5 membrane have no significant changes after being immersed in 60? 1M KOH solution for a certain time.Demonstrates excellent performance.