Study On Modification Of Diffusion Layer To Improve PEMFC Oxygen Mass Transfer Performance

Proton exchange membrane fuel cells have outstanding characteristics such as high energy conversion efficiency;environmental friendliness;rapid startup at room temperature;and no electrolyte outflow under working conditions.The development prospect is very broad,especially as a power source for electric vehicles,however,as an automobile power source,poor durability is always an important research direction.Whether it is the problem of instantaneous dynamic response or the problem of high current density discharge,it will seriously affect the performance and life of the battery,which is related to the cathode oxygen mass transfer rate is too slow.In order to alleviate the oxygen mass transfer problem,this article will start from the following aspects.First,the nano-scale oxygen storage material CeO₂was prepared by precipitation method and hydrothermal method.Then through TG-DTA,SEM,XRD and TEM characterization methods to determine the best process parameters.The best process parameters of the precipitation method are:the concentration of cerium nitrate is 0.3 mol/L,the concentration of ammonia is 1 mol/L,and it is calcined at 500°C for 2h;The best process parameters of hydrothermal method are:1 g cerium nitrate,10 ml deionized water,20 ml ethylene glycol and 1 ml glacial acetic acid,0.8 g PVP,after mixing uniformly,the hydrothermal reaction was carried out in a high-pressure reaction kettle at 22 h and 180°C,and the reaction precursor was calcined at 500°C for 2 h.The CV test shows that the presence of nano-CeO₂can significantly improve oxygen storage and release capacity,and the effect of the nanometer hollow sphere CeO₂prepared by hydrothermal method is better.SEM,EDX and BET tests were performed on the traditional diffusion layer and the modified diffusion layer added with CeO₂,the test shows that it has been successfully added to the diffusion layer,the contact angle and contact resistance tests show that CeO₂does not significantly change the hydrophilicity/hydrophobicity and conductivity of the diffusion layer,among them,the hydrothermal preparation of CeO₂has less effect on conductivity.In order to deeply study the influence of CeO₂on oxygen mass transfer performance,the polarization curve,AC impedance and response tests were performed on the single cell,The results show that the addition will significantly reduce the mass transfer polarization phenomenon and the reaction internal resistance of the battery;improve the response dynamic response speed,among them,the effect of hydrothermal preparation of CeO₂is more significant.The battery performance has been improved by 10%and the drop in loading voltage has been reduced from 30.16%to 12.74%,response time increased by 59.3%,stable voltage increased by 7.29%,it is further proved that the addition of CeO₂improves the oxygen mass transfer performance of the battery.