The Study On Microstructure And Performance Of SPEEK Based Nanofiber Composite Proton Exchange Membrane

In this paper,sulfonated polyether ether ketone（SPEEK）is selected as the matrix of the proton exchange membrane.In view of the low degree of separation of the hydrophilic-hydrophobic phase of SPEEK,it is difficult to balance high dimensional stability and high conductivity.Nanofiber composite can ensure that the composite membrane has high dimensional stability.Reducing the activation energy of proton conduction by regulating the content of proton conducting groups in SPEEK.Fiber functionalization can adjust the type and structure of functional groups at the interface between the fiber and the matrix,and explore the effect of the interface on proton conduction.First,phosphotungstic acid（HPW）and pre-oxidized polyacrylonitrile（PPNF）nanofibers were co-blended to prepare HPW/PPNF/SPEEK fiber composite membranes.HPW increases the concentration of ion clusters in the composite membrane and reduces the activation energy required for proton transport.PPNF nanofibers have excellent solvent resistance,build a complete three-dimensional fiber network in SPEEK,inhibit the swelling of the composite membrane,and limit the loss of HPW.The proton conductivity of the 20%HPW/PPNF/SPEEK fiber composite membrane at 100%RH and60℃is 141.9m S·cm^-1,and its area swelling rate is 83.6%of the original SPEEK membrane.The PPNF-coated SU6@PPNF nanofibers with SO₃H-UiO-66（SU6）were prepared by in-situ hydrothermal,and then combined with SPEEK to form a membrane.In the hydrated state,the SU6@PPNF-SPEEK fiber composite membrane exhibits excellent proton conductivity,dimensional stability and mechanical strength.SU6@PPNF is rich in sulfonic acid groups,which increases the content of sulfonic acid groups and free water adsorption at the interface between the fiber and the matrix,realizing efficient proton conduction.The conductivity of the membrane is 156.4 m S·cm^-1 in the hydrated state at60°C.It provides a new design scheme for the preparation of high-performance proton exchange membrane channels.Amino-functionalized NU6@PPNF nanofibers coated with NH₂-UiO-66（NU6）PPNF were prepared by in-situ hydrothermal synthesis.The fibers have excellent solvent resistance and polymer compatibility.Compared with the original SPEEK film,the dimensional stability of the 1.3%NU6@PPNF-SPEEK composite film in the hydrated state at 60°C is increased by 30%.Due to the interaction between NU6 and-SO₃H,an acid accumulation layer is formed along the fiber that can achieve efficient proton transport,reducing the activation energy required for proton transport.In addition,this work is the first to analyze the formation mechanism of the acid accumulation layer through in-situ Fourier infrared spectroscopy（FTIR）and X-ray energy spectroscopy（EDS）,which provides support for the construction and adjustment of proton transmission channels.The PSPMA-g-PVDF was anchored on the surface of PPNF nanofibers by in-situ hydrothermal heating of PSPMA-g-PVDF and NU6 precursor to prepare PSPMA-g-PVDF@PPNF nanofibers,and combined with SPEEK to form a film.P-g-P@PPNF-SPEEK composite film has excellent dimensional stability.The anchoring effect of NU6on PSPMA-g-PVDF and the rich sulfonic acid groups of PSPMA-g-PVDF,PSPMA-g-PVDF@PPNF increases the concentration of sulfonic acid groups at the interface between the fiber and the matrix through a unique phase separation structure Optimize the arrangement of ion clusters to form a highly connected low energy barrier proton transport channel.With the increase of PSPMA-g-PVDF coating amount,the proton conductivity increases.It provides a new design idea for the preparation of proton exchange membranes with high proton conductivity and high stability.