Preparation And Performance Of Novel Amino Quaternary Phosphonium Cation Membrane Materials

Alkaline fuel cells greatly reduce manufacturing costs by using common non-precious metals as catalysts.However,as one of the core components in AEMFCs,anion exchange membranes still face some challenges,such as low ionic conductivity and poor alkali resistance,which severely limits their commercial applications.Therefore,the development of high-performance,long-life polymer materials is an urgent task that needs to be solved.In this paper,two kinds of tetrahydropyrrolidinyl quaternary phosphonium(BAPP)and cyclohexylamine quaternary phosphonium(TCPC)with large steric hindrance were successfully synthesized and loaded on polyphosphazene and polyphenylene ether backbone to prepare a series of new anion exchange membranes.The prepared alkaline membrane was tested for performance including SR,WU,IEC,TSB,ionic conductivity and alkali stability.The PBAPP-POH-45%polyphosphazene alkaline membrane with an IEC value of 0.77 mmol/g displayed the hydroxide conductivities of 28.5 mS·cm-1 at 80?,and showed excellent alkaline stability that only 5.3%hydroxide conductivity degradation was observed after being exposed to 2.0 M KOH at 60? for 50 days.PPO-TCPC-70 polyphenylene ether alkaline membrane exhibits higher ionic conductivity due to its partial quaternization functional group and high functionalization ratio.The ionic conductivity was 40.6 mS·cm-1 at 80?.However,due to the grafting of quaternary ammonium groups,the alkali stability has been significantly reduced.It was observed that the ionic conductivity decreased to 68%after being exposed to 2.0 M KOH at 60? for 50 days.In order to improve the ionic conductivity of the membrane without affecting the basic alkali resistance,the polyphosphazene polymer grafted with BAPP quaternary phosphonium cation was blended with PVA and then crosslinked with glutaraldehyde to prepare a series of PBAPP-PVA-x composite membranes.Through testing,it is concluded that when the proportion of PBAPP polymer in the blend system is 40%,the overall performance of the composite membrane is optimal.The PBAPP-PVA-40%composite membrane displayed the hydroxide conductivities of 43.9 mS·cm-1 at 80?,and showed excellent alkaline stability that only 6%hydroxide conductivity degradation was observed after being exposed to 2.0 M KOH at 60? for 50 days.This work provides a feasible method for improving the chemical stability of the functionalized quaternary phosphonium anion exchange membrane.