| Anion exchange membrane fuel cells（AEMFCs）have attracted extensive attention and research due to the advantages of using non-precious metal catalysts and low redox potential.Anion exchange membranes（AEMs）,which are the core components of fuel cells,function to transport hydroxide ions and separate the anodes and cathodes.However,the shortcomings of AEMs with low conductivity and poor stability limit the practical application.This dissertation discusses the regulation of free volume in membranes to improve the conductivity of AEMs,two experimental routes of blending and chain extension are used,and the microporous polymer（PIM）with high free volume characteristics is used to promote microphase separation.The main research contents are as follows:1.PIM blending.Quaternized polysulfone was used as the main component of membranes,and PIM with low quaternized degree was used as the blending component to prepare the blended AEMs（MmPSF/MmPIM-X）with gradient PIM content.The MmPSF membrane has the lowest conductivity of 11.5 mS cm-1 at 30℃ and the BET specific surface area(SBET)of only 41 m2 g-1.After PIM blending modification,SBET increased to 119 m2 g-1,and the ion exchange capacity（IEC）decreased from 1.08 to 0.77 mmol g-1,obvious ion clusters appeared in the membrane and he diameter reaches 7 to 8 nm,and the conductivity increases to 16.9 mS cm-1 indicating that increasing the free volume promotes the microphase separation and enhances the conduction of hydroxide ions.PIM rigid structure enhanced the tensile strength of the blend membranes.Compared with MmPSF,the tensile strength of the membrane containing30%PIM increased from 36 MPa to 43 MPa,and MmPSF/MmPIM-30%has a good cell performance with a peak power density of 163 mWcm-2 at 60℃.2.PIM chain extension.The free volume effect and block effect promote the microphase separation by using PIM as the hydrophobic segment of the polymer backbone.Fluorine group-terminated polysulfone and hydroxy group-terminated PIM were condensed to prepare block polymers（PIM-b-PSF）,followed by chloromethylation and quaternization to prepare PIM chain extender AEMs.After the chain extension reaction,the SBET of DMBA-PIM-b-PSF-0.91 membrane increased from 69 to 85 m2 g-1,and the conductivity reached 52.6 mS cm-1 at 80℃ while DMBA-PSF-1.24 membrane is only 41 mS cm-1.The DMBA-PIM-b-PSF-0.91 membrane has a peak power of 270 mWcm-2 at 80℃ and 0.1 MPa back pressure.In summary,the aim of this dissertation is to solve the problem of discontinuous transfer channel under low IEC level and the long-term stability of quaternized PIM is insufficient.PIM was used as a micropore regulator to increase the free volume in membranes and promote ion cluster penetration,which has important theoretical significance for the practical development of AEMFCs. |
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