Study On Preparation Process And Performance Optimization Of PEMFC Gas Diffusion Layer

Proton exchange membrane fuel cell（PEMFC）has many advantages,such as clean and pollution-free,high energy conversion efficiency,wide working temperature range,high safety and reliability.PEMFC produces more water when working at high current density.If the generated water cannot be discharged quickly,it is easy to block the plug hole with water,resulting in the reduction of battery performance.The gas diffusion layer（GDL）between the catalytic layer（CL）and the bipolar plate plays a decisive role in the water management and reaction gas transportation capacity of PEMFC.Therefore,in view of the important role of GDL in water vapor transmission,starting from the material and structural characteristics of GDL,this paper designs a gas diffusion layer（GDL）with good characteristics to improve the water vapor management ability and reduce the manufacturing cost of PEMFC,and uses hydrogen and air as reaction gases to test its electrochemical performance.The main research contents and achievements are as follows:（1）The effects of different thickness of substrate on fuel cell performance and water management were studied.When the thickness of carbon paper is 180μm.The maximum porosity of carbon paper is 74.07%.It has more mesopores and pores,which is conducive to gas diffusion,water management and mass transfer of liquid water.When GDBL thickness is 180μm,under the condition of 60%humidification,the ultimate power density of fuel cell can reach 0.523w/cm~2,which is 53.4%higher than that of commercial gas diffusion layer;Under the condition of 100%humidification,the limit power density can reach 0.585w/cm~2,which is 25.1%higher than the limit power density of commercial gas diffusion layer of 0.468w/cm~2.（2）The influence of the hydrophobic performance of the base layer on the performance of the fuel cell was studied,and the performance of the fuel cell was studied under the conditions of 60%humidification and 100%humidification.The results show that with the increase of PTFE content,the proportion of hydrophobic holes in the overall hole distribution increases,which is more conducive to water gas transmission.When the PTFE content is 20%,the ultimate power density under 60%humidification can reach 0.546w/cm~2,which is 60.1%higher than that of commercial gas diffusion layer;Under 100%humidification,the ultimate power density can reach0.538w/cm~2,which is 14.9%higher than that of commercial gas diffusion layer.（3）The effect of XC-72/CNTs on the pore size distribution of gas diffusion layer and the performance of fuel cell was studied.The results showed that when the ratio of carbon nanotubes to XC-72 was 5:5,the microporous layer prepared by the composite of the two conductive materials combined the advantages of the two materials and had a more reasonable pore structure;When the conductive materials contained in the microporous layer in the prepared GDL are 50%CNTs and 50%Vulcan XC-72,the ultimate power density can reach 0.487w/cm2 under 60%humidification,which is 42.8%higher than that of the commercial gas diffusion layer;Under 100%humidification,the ultimate power density can reach 0.592w/cm2,which is 26.5%higher than that of commercial gas diffusion layer.（4）The effect of electrospinning process on the performance of fuel cell was studied.In electrospinning,PTFE is used as hydrophobic material and carbon nanotube is used as conductive material to prepare conductive hydrophobic composite fiber membrane with excellent performance.When MPL on GDL is spun from spinning solution containing 0.6g conductive carbon black,its ultimate power density can reach 0.417w/cm~2under 60%humidification,which is 22.3%higher than that of commercial gas diffusion layer.Therefore,compared with commercial GDL,this paper further optimizes the internal structure and material composition of GDL,which has outstanding advantages in further improving the water and gas management ability in fuel cell and reducing resistivity,and provides new development ideas and methods for the development of GDL and overcoming the key technical bottleneck of fuel cell.