Fabrication And Performance Research Of Nanofiber Microporous Layer Of Fuel Cell

Proton exchange membrane fuel cell(PEMFC)has many advantages,including high power density,high energy conversion efficiency,no pollution,high reliability,and low noise,so it is used as an energy conversion device and has achieved rapid development.However,PEMFC is currently facing some problems,and its technical bottlenecks are particularly prominent.PEMFC produces more water when working at high power densities,resulting in untimely drainage and easy flooding,so the performance declines rapidly.In addition,PEMFC due to the formation of super-cooled water is easy to freeze during the cold start,which makes the cold start unsuccessful,and the freezing of super-cooled water will cause rapid aging of fuel cell performance.Microporous layer(MPL)between catalyst layer(CL)and gas diffusion layer substrate plays a decisive role in the water management and gas transport of PEMFC.Therefore,in view of the technical bottlenecks faced by fuel cells,this master thesis uses electrospinning technology to prepare a new type of nano fiber structure microporous layer,that is,electrospinning MPL.The main research contents and results are as follows:(1)Electrospinning MPL was successfully prepared by electrospinning technology.The formulation of electrospinning MPL uses non-toxic,low-cost anhydrous ethanol as a solvent,and is formed by uniformly mixing the ratio of polyvinylpyrrolidone:acetylene black:anhydrous ethanol?1:0.2:11.5.Through experiments,suitable electrospinning and heat treatment conditions were explored,and the prepared MPL had good nanofiber morphology and three-dimensional network structure.Compared with commercial MPL(SGL-29BC),electrospinning MPL has a smaller water contact angle and larger pores,and its capillary breakthrough pressure is less than commercial MPL.(2)Through the fuel cell tests,it was found that under 70? and 100%relative humidity,the performance of electrospinning MPL is much better than that of commercial MPL,and the performance gap is more obvious with the increase of current density,mainly because electrospinning MPL has a lower capillary pressure and a more developed three-dimensional fiber network structure,which can effectively promote the discharge of liquid water under high current density conditions,thereby improving the water management capability of fuel cell.(3)Through cold start experiments at-10? and-15 ?,it was found that the cold start capability of electrospinning MPL is much higher than that of commercial MPL,mainly because electrospinning MPL is composed of nanofibers with a certain degree of flexibility.The good interface contact with the CL,and the lower capillary pressure caused the super-cooled water to be discharged more smoothly from the CL.The commercial MPL has a particle-packed structure,and the capillary pressure of its pores is larger,which makes it difficult for the super-cooled water to break through the pores of the commercial MPL,thereby super-cooled water easily freezing,resulting in poor cold start capability.(4)Through the fuel cell test after cold start,it was found that the presence of electrospinning MPL can effectively slow down the performance aging of the fuel cell during cold start,mainly due to the higher durability of nanofiber type electrospinning MPL,and it can alleviate the damage to the catalyst layer caused by the freezing of super-cooled water.Therefore,compared with commercial MPL,electrospinning MPL has obvious advantages for improving the normal temperature performance and cold start capability of fuel cells,and improving water management.Electrospinning MPL Provides new idea for the development of MPL and to solve the technical bottlenecks of fuel cells.