Study On The Preparation And Performace Of Cross-linked PDDA/quaternized Chitosan Anion Exchange Blend Membrane

Alkaline Anion Exchange Membrane Fuel Cells(AAEMFCs)allow the use of nickel,silver,cobalt and other non-noble metals as catalysts,greatly reducing production costs,and the OH~-conduction direction is opposite to that of fuel infiltration,which can alleviate fuel infiltration and avoid short circuits accident.Aimed to two main problems existed in the current research process of alkaline anion exchange membrane(AEMs):(1)low ionic conductivity;(2)poor mechanical properties and chemical stability,in this paper two different anion exchange membranes were prepared from chitosan(CS)and 2,3-epoxypropyltrimethylammonium chloride(GTMAC),as follows:(1)GTMAC is grafted onto the side chain of CS through an epoxy ring-opening reaction,and then KH560 is also bonded to the CS side chain through an epoxy ring-opening reaction.Finally,quaternized chitosan anion exchange membranes with different cross-linking degree were prepared by sol-gel process.FTIR results show that GTMAC was grafted onto CS successfully,and the siloxane in KH560 was successfully hydrolyzed and condensed to form a three-dimensional network structure of Si-O-Si.XRD tests show that the prepared film is amorphous.The film also has good thermal stability and can stably exist within 200?.SEM results exhibit that the microstructure of the membrane is homogeneous and compact,no phase separation is observed.The IEC value does not change much with the increase of cross-linker usage.The analysis of water absorption show that the addition of cross-linking agent can effectively control the swelling of the membrane,ensuring good dimensional stability and mechanical properties.The ionic conductivity gradually decreased with the increase of the cross-linker usage and the membrane ionic conductivity reached 12.8 mS/cm at 80?,which has a certain use value.Alkaline resistance test results show that after immersed in8mol/L KOH solution for 360h,the OH~-conductivity of the membrane was 6.3mS/cm,exhibiting that the addition of the cross-linker is beneficial to improve the chemical stability of the prepared membrane.(2)GTMAC was firstly grafted onto the CS side chain by epoxy ring-opening reaction,then PDDA was mechanically blended to form a homogeneous system.Finally,PDDA/quaternized chitosan anion exchange membranes with different PDDA doping contents were prepared by sol-gel process.FTIR test results show that PDDA was successfully doped into the system.XRD tests show that the prepared film is amorphous.SEM results show that with the increasing amount of PDDA,the internal structure of the film becomes more and more loose,and finally there is a clear phase separation phenomenon.The mechanical performance test results also support the existence of phase separation phenomenon.With the increase of PDDA doping amount,the tensile strength increases first and then decreases sharply.The TG test results show that the prepared films has good thermal stability within 200°C,which can meet the practical needs.IEC and WU values increased with the increasing amount of PDDA.The ionic conductivity test results show that the doping of PDDA can effectively improve the ionic conductivity of the membrane.The ionic conductivity can reach37.9mS/cm at 80°C,showing good ionic conductivity performance.Alkaline resistance analysis show that due to the large steric hindrance of the five-membered ring structure in PDDA,doping of PDDA can increase the chemical stability of the anion exchange membrane.