The Study Of Hydrophobic And Hydrophilic Microporous Layer Proton Exchange Membrane Fuel Cell By Electrospinning

The proton exchange membrane fuel cell is an efficient energy conversion device,which has the advantages of low environmental pollution,high conversion efficiency and low start-up temperature.One of the constraints to the large-scale commercial application of PEM fuel cells is the water management of the fuel cells.The purpose of water management is to ensure adequate wetting of the proton membrane and ionomer electrolyte within the catalytic layer to reduce the proton conduction impedance,while avoiding “water flooding” within the porous transport medium and blocking gas transport.Microporous layer,as one of the key components of fuel cells,its main function is to achieve reasonable water management of fuel cells.The ideal microporous layer can keep the water content in the fuel cell within a reasonable range,so that the fuel cell can exert excellent performance.In this paper,various types of electrospun microporous layers were prepared by electrospinning method.The final prepared hydrophilic-hydrophobic composite bilayer microporous layer has good performance under various working conditions.The research of this paper can be divided into two parts.The first part is the preparation and properties of electrospun monolayer microporous layer.First,a hydrophobic electrospun monolayer microporous layer was prepared by electrospinning technology and subsequent heat treatment technology using hydrophobic acetylene black,anhydrous ethanol and PVP as raw materials.Its micron-scale pore size and high porosity provide good channels for material transport in fuel cells.Although the water contact angle of the hydrophobic electrospun monolayer microporous layer is lower than that of the commercial microporous layer,its large pore size pores are more conducive to the discharge of liquid water,which enables the assembly of the hydrophobic electrospun monolayer microporous layer on the cathode side.Layered fuel cells outperformed commercial microporous layers at 100% relative humidity and large current densities.However,the poor water retention capacity of the hydrophobic electrospun monolayer microporous layer makes its performance at low relative humidity poor.Secondly,a hydrophilic electrospun single-layer microporous layer was prepared by electrospinning technology and subsequent heat treatment technology using hydrophilic pigmented carbon black,anhydrous ethanol and PVP as raw materials.The surface of the single fiber of the hydrophilic electrospun monolayer microporous layer is uniformly covered with hydrophilic carbon black,which makes it show good water retention capacity.The hydrophilic electrospun monolayer microporous layer exhibited better performance than the hydrophobic electrospun monolayer microporous layer when the fuel cell was operated at low relative humidity.This is mainly because under dry conditions,the hydrophilic electrospun single-layer microporous layer retains the water generated by the reaction in the fuel cell,which increases the water content of the CL and the proton membrane,and then increases the three-phase reaction area of CL.And reduce the proton resistance,thereby improving the performance output of the fuel cell.Finally,PAN-based electrospun microporous layers were prepared using PAN and PVP as raw materials.The single fiber surface of the PAN-based electrospun microporous layer is smoother and the fiber distribution is more dense.Although the PAN-based electrospun microporous layer has good hydrophilic properties,its bulk resistance is too high,so that the ohmic overpotential of the fuel cell during operation is much higher than that of the commercial microporous layer,resulting in poor cell performance.The second part is the preparation and properties of the electrospun bilayer microporous layer.The electrospun double-layer microporous layer is to continue to prepare a hydrophilic electrospun single-layer fiber membrane on the surface of the hydrophobic electrospun single-layer fiber membrane,and then heat treatment to prepare a hydrophilic and hydrophobic composite double-layer electrospun microporous layer.The thickness of the hydrophilic and hydrophobic layers is controlled by the spinning time.At low relative humidity,the electrospun bilayer microporous layer outperformed the hydrophobic electrospun monolayer microporous layer,which is due to the water retention capacity of the hydrophilic layer increasing the water content in the fuel cell.However,the performance of the electrospun bilayer microporous layer was slightly lower than that of the commercial microporous layer.After IR-free,the performance of the electrospun bilayer microporous layer was better than that of the commercial microporous layer.The reason for this is the higher ohmic impedance introduced by electrospun bilayer micropores,which is related to its bilayer structure.In this paper,various electrospinning microporous layers were developed,and their structural characteristics and fuel cell performance were systematically studied,which provided ideas and technical solutions for faster commercial application of fuel cells.