Preparation And Properties Of Ionic Liquid Modified PPO Anion Exchange Membranes

Fuel cell is a kind of environment-friendly new energy with high efficiency.At present,it has been widely used in various fields of society.Anion exchange membrane(AEM)is one of the core components of anion exchange membrane fuel cell.However,the poor ion conductivity and poor alkali resistance of anion exchange membrane restrict its application.Poly(2,6-dimethyl-1,4-phenylene oxide)(PPO)is suitable for the polymer skeleton of anion exchange membrane because of its low cost,excellent chemical stability and thermal stability.With PPO as the main chain,a series of PPO based anion exchange membranes are prepared,and their characterization and performance studies are carried out.The specific research is as follows:(1)A series of imidazole functionalized PPO based AEMs are prepared.Nbromosuccinimide was used in brominated PPO.Then four imidazole compounds(N-methylimidazole,N-butylimidazole,1,2-dimethylimidazole and 1-butyl-2-methylimidazole)are selected and their functions are modified.The solution casting method was used according to the fixed feed ratio.In this paper,a series of imidazole functionalized PPO anion exchange membranes are tested for physical properties,electrochemical properties,and alkali resistance.The test results show that the IEC,water uptake and swelling ratio of different membranes are different,but the ionic conductivity basically meets the performance requirements.At the same time,the membrane with 1-butyl-2methylimidazole as functional group has the best alkali resistance.After 200 hours of alkali treatment,the ionic conductivity of the membrane remains about 90%.(2)In order to further improve the ionic conductivity of the membrane,different brominated degrees of brominated PPO are prepared to explore the effect on the ionic conductivity of the membrane.According to the test results,with the improvement of membrane functionality,the ionic conductivity is also increased.However,in the process of testing,when the bromination degree increase to about 45%,the water swelling of the membrane is more serious,and the deformation is obvious,resulting in a decrease of the mechanical properties of the membrane,which is unfavorable to the use of the membrane.(3)In order to further improve the ionic conductivity of the anion exchange membrane,PPO ionic liquid composite membranes doped with ionic liquid are prepared.In this paper,34%brominated PPO is selected as the main chain,and 1-butyl-2-methylimidazole is used as the functional modification material.At the same time,two kinds of ionic liquids are prepared and doped into the membranes,and nano-TiO2 is introduced to immobilize the ionic liquid.According to the membrane test,the maximum ionic conductivity of the composite membrane reaches 67 mS/cm.After alkali treatment,some membranes still have 80%ionic conductivity.Compared with "increasing bromination degree" to improve the ionic conductivity of the membrane,this method can improve the ionic conductivity of the membrane and effectively reduce the swelling of the membrane.