Study On Alkaline Anion Exchange Membranes With Ammonium Groups

As the core component of Alkaline anion exchange membrane fuel cell(AAEMFC)and Alkaline Anion Exchange Membrane electrolysis(AAEME),alkaline anion exchange membranes separate electron and reactants and conduct OH-in the cells.Their future commercialization will hugely contribute to the development of AAEMFC and AAEME,further making the cells instead of the fossil fuel to reduce the mitigation of air pollutants and carbon dioxide.However,there are mainly two huge challenges restricting their development,the relatively low conductivity and chemical stability.So the development of highly stable and conductive AAEMs are the focus in the R&D.This dissertation focuses on the stability and ion conductivity of AAEMs,and the relationship between the performance and structure by designing the molecular structure.The main research results are as follows:Firstly we take good use of Semi-interpenetrating polymer network(semi-IPN)to solve the problem of unavailability of poly(4-vinylbenzyl ammonium)(PVBA)film forming.To achieve a chemically stable AAEM,C-H main chain and trimethylbenzyl ammonium functional group are selected since their excellent chemical stability.However combining them two gets the poly(4-vinylbenzyl ammonium)and it couldn't form membranes.So in this work through bringing in PBI to get a semi-IPN to solve the problems.PBI has excellent mechanical properties so as to keep the semi-IPN with higher IEC,thus leading to a highly conductive AAEM,which solves the problem that traditional semi-IPN AAEMs always have too low conductivity.Since the mole ratio of PVBA and PBI and the contents of cross-linking agents could have an influence on the physical and chemical properties,ion conductivity,mechanical properties and chemical stability of the membranes,their influences on membranes are discussed in the work.Finally,PVBA-4PBI,10%cross-linking agents have better properties(tensile stress 15.5MPa,elongation at break 60%),showing great potential in future application.Secondly multi-cation AAEMs are designed and synthesized to solve the problem that SEBS AAEMs always have too low conductivity.This work starts from the structures of each part(such as the numbers of functional group,the carbon chain between two functional groups and the carbon chain at the back ends)to study the structure and performance relativity.Simultaneously,we develop an membrane casting technique that can easily handle the thickness of SEBS AAEMs.Finally SEBS-N2C6-C6 processes excellently on physical and chemical properties and conductivity,which has a bright future to volume production.