Design And Preparation Of Novel Alkaline Anion Exchange Membrane Based On Poly Ionic Liquids

Polymer electrolyte fuel cells regarded as a new generation of revolutionary energy devices have many advantages such as high safety,high power density,low start-up temperature,and so on.According to the type of conducting ions,polymer electrolyte fuel cells are divided into two major categories: proton exchange membrane fuel cells(PEMFCs)and alkaline anion exchange membrane fuel cells(AAEMFCs).Compared with the widely used commercial PEMFCs,AAEMFCs have the outstanding advantages such as avoiding the use of noble metal catalysts on the electrodes and reducing the cost of fuel cells,which has great potential for commercial production.Anion exchange membranes as the core components of AAEMFCs directly determine the working life and output power of fuel cells.Poor stability and low ionic conductivity are issues that are urgently needed in current AEMs.This study designed and prepared organic membranes with comb shaped side chains and bis-functional cross-linked structures,MOF materials with long-term ordered cage channels was dispersed homogeneously into the an imidazolium-functionalized poly(2,6-dimethyl-1,4-phenylene oxide)to prepare hybrid membranes containing auxiliary ion channels.Optimizing the molecular structure: polymerized ionic liquid composed of two ionic liquid precursors,1-allyl-2-methylimidazole and 1-butyl-2-methylimidazole,and a poly(ionic liquid)main chain p(St-co-VBC)were synthesized via quaternization reaction to prepare anion exchange membranes(AEMs).The two ionic liquid precursors were synthesized from 2-methylimidazole.The poly(ionic liquid)main chain was prepared from styene(St)and p-chloromethylstyrene(VBC).The prepared membranes possessed crosslinked and comb shaped side-chain structure.Fourier transform infrared,scanning electron microscopy and thermogravimetry were used to investigate the molecule structure,morphology,hydroxide conductivity,thermal stability,alkaline stability and other properties of the membranes.The results showed that the AEMs had quite low water uptake,36.7%~93.4%,and the ion exchange capacity was 1.61~2.16 mmol/g.The conductivity of p(St-co-VBC)-3AEMs was as high as 68.4 ms/cm at 80 ?.The AEMs displayed excellent alkaline stability and the hydroxide conductivity of p(St-co-VBC)-3 AEMs was still as high as52.2 ms/cm after immersing in 1 M Na OH solution for 240 h.Building assisted rigid ion channel: in this study,an imidazolium-functionalized poly(2,6-dimethyl-1,4-phenylene oxide)was used as a base film,and a MOF with ordered pore and rigid cage structure was used as a hybrid nano materials.The poly ionic liquid monomer was immersed in the MOF via a supercritical impregnation method,and restricted in the pores after in-situ polymerization,the specific surface area of MIL101 decreased from 2750m~2/g to 57m~2/g.Then the MOF loaded by poly ionic liquid was mixed with the base membrane.The basement membrane maintained the original ion channel of microphase separation,and the assisted ion channel was constructed through the long-term ordered pores of the MOF itself and the internal electrolyte.The hybrid AEMs demonstrated a low swelling ratio(12.1%)while the ion exchange capacity of hybrid membrane was up to 2.97 mmol/g,the hydroxide conductivity residual ratio of hybrid membranes reached to 76% after alkaline soaking for 96 h,the peak ion conductivity of the hybrid membrane was as high as139.2 ms/cm at 80 ?.The alkaline stability,thermal stability and mechanical strength of the hybrid AEMs were improved while the ion transmission was enhanced.