Preparation Of Alkali-Resistant Anion Exchange Membrane

Fuel cells have become a new generation of energy technology after solar energy,wind energy and water energy due to the advantages of low pollution emissions and high energy conversion efficiency.Among them,the anion exchange membrane fuel cell has been gradually paid attention to people by its simple structure,no need to use a precious metal catalyst,and low preparation cost.As the core component of the fuel cell,the anion exchange membrane plays the role of conducting ions and isolating the electrodes,and its performance affects the performance and service life of the fuel cell directly.Therefore,many scholars have begun to study anion exchange membranes in recent years,among which quaternary ammonium base on anion exchange membranes are the most widely studied.However,since the working environment of the anion exchange membrane is alkaline,hoffman degradation and nucleophilic substitution reaction are apt to occur,causing the quaternary ammonium cationic group to be attacked and dropped or even the skeleton is degraded,thereby lowering the electrical conductivity.It is also an important reason for limiting the further development of anion exchange membranes.Therefore,it is important to find an anion exchange membrane with high alkali stability.In this paper,the following method was used to prepare an anion exchange membrane,which was designed to improve the alkali resistance of the membrane while maintaining the other properties of the membrane.Firstly,quaternized chitosan（QCS）and polyvinyl alcohol（PVA）are used as an anion exchange membrane matrix,the two substance are blended and crosslinked by using glutaraldehyde as a crosslinking agent,to prepare the semi-interpenetrating network anion exchange membrane with space of network structure.The quaternized chitosan/polyvinyl alcohol anion exchange membrane was immersed in 6.0 mol/L KOH for 240 h to investigate its alkali stability.The results show that the membrane can still exist stably under alkali conditions,the conductivity decreased after soaking for 240 h,which was about 20%of the initial membrane.Secondly,β-cyclodextrin（β-CD）was introduced,and quaternized chitosan,polyvinyl alcohol andβ-cyclodextrin were added by means of glutaraldehyde（GA）and melamine（MA）as a joint crosslinking agent.A series of host-guest complex-type anion exchange membrane based on cyclodextrin molecules are prepared.In the course of experiment,the cavity structure unique to cyclodextrin is used to complex the metal Ca²⁺for OH-conduction,in the same time,the dense network structure"protects"the quaternary ammonium N⁺cationic group in the network structure,thereby improving the alkali resistance of the membrane structure.The results show that theβ-cyclodextrin/quaternized chitosan/polyvinyl alcohol anion exchange membrane was immersed in 6.0 mol/L KOH for 240 h,and the conductivity decreased by about 17%of the initial membrane.Thirdly,using polysulfone（PSF）as a polymer film matrix,a Gemini-type polymerizable cationic surfactant monomer[diethyl maleate bis（octyldimethyl chloride/bromination Ammonium）(G_8-2-8),diethyl maleic acid bis（dodecyldimethyl chloride/ammonium bromide）(G_12-2-12),maleic acid diethyl Ester-based bis（hexadecyldimethyl chloride/ammonium bromide）(G_16-2-16)]was introduced into the polysulfone chloroform casting solution,with the help of potassium persulfate as initiator,the in-situ initiation polymerization of Gemini was used to construct an ordered arrangement of cationic active sites.The anion exchange membrane of the channel was investigated for its alkali stability.The results show that after the Gemini/polysulfone anion exchange membrane was immersed in 6.0 mol/L KOH for 240 h,its electrical conductivity droped by only 2.0%of the initial membrane.