Proton/Thermal Conduction And Reaction Characteristics Of Electrospun Nanofibers For Polymer Electrolyte Fuel Cells

Proton exchange membrane fuel cell with high power density under low platinum loading is the core technology for large-scale commercialization of fuel cell vehicles.Catalyst layer,as the core component of fuel cell,needs to operate at high current density under low platinum loading.The nanofiber alignment catalyst layer with ordered structures has shown excellent performance under low platinum loading,and has become a research hotspot in the field of fuel cell catalyst layers.However,the mechanism underlying the performance improvement of the nanofiber alignment catalyst layer is unclear.The structure and characteristics of its basic structural unit,nanofiber,lack research,making the future direction of optimization unclear.To address these issues,this thesis firstly developed the method for proton and thermal conductivity measurement of single nanofiber,and then analyzed its proton and thermal conduction characteristics.After that,the structure-property-performance relationship of the nanofiber alignment catalyst layer was studied.This study is divided into four parts.The first part focus on the preparation and structure regulation of electrospun nanofibers.This part determines the preparation process of electrospun nanofibers,and finds out the influence of slurry parameters,electrospinning parameters and environmental parameters on the electrospinning behavior,and analyzes the relationship between preparation parameters and nanofiber structures.Nanofibers with setting sizes and carrier polymer contents were well prepared.The second part designs the micro-electrode chip for proton conductivity measurement,and develops the method for manipulating and fixing nanofibers.A measurement system for proton conductivity measurement of single nanofiber was established.Based on this,the effects of carrier polymer,relative humidity,and nanofiber size on the proton conductivity of ionomer nanofibers were analyzed.The third part designs the microelectrode chip and develops the method for measuring the thermal conductivity of nanofibers while eliminating the effect of contact thermal resistance.A measurement system for thermal conductivity measurement of single nanofiber was established.Based on this,the thermal conductivity of ionomer nanofibers and composite nanofibers was characterized,and the mechanism of their superior thermal conductivity was analyzed.The fourth part prepared nanofiber alignment catalyst layers with low platinum loading,including the ionomer nanofiber scaffolding catalyst layer and the composite nanofiber alignment catalyst layer.The effects of cross-sectional component distribution and ionomer content of nanofibers on the performance was investigated,and the optimization direction of the nanofiber alignment catalyst layer was identified.This study presents the controllable preparation method for electrospun nanofibers and nanofiber alignment catalyst layers,and explores the performance improvement mechanism of nanofiber alignment catalyst layers with ordered structures.It innovatively analyzed the proton conduction and thermal conductivity characteristics of nanofibers at the mesoscale,providing theoretical support and technical solutions for understanding the structure-performance relationship of nanofiber alignment catalyst layers and developing catalyst layers operating at high current density under low platinum loading.