Preparation And Performance Optimization Of Membrane Electrode Assembly For Proton Exchange Membrane Fuel Cell

Due to its high energy efficiency,and non-pollution,proton exchange membrane fuel cell(PEMFC)has extensive fine prospects in the field of new energy vehicles.However,the large-scale commercialization of PEMFC is still limited by insufficient performance.Membrane electrode assembly(MEA)is the core component of PEMFC.It is necessary to deeply understand the electrochemical reaction mechanism and transfer process in the MEA to further improve the performance of PEMFC.Combined with the current development trend of hydrogen energy,the purpose of this research is to pursue the MEA with high performance and high power-density.Focusing on the cathode catalyst layer,the synthesis of cathode catalyst and the composition allocation of cathode catalyst layer were studied emphatically.Moreover,an improved three-dimensional multiphase non-isothermal PEMFC numerical model was proposed to guide the performance optimization of MEA.The main research contents and results are as follows:(1)Synthesis and characterization of catalysts:Firstly,the synthesis of Pt Cu/C alloy catalyst by microwave heating method was explored to provide guidance and reference for the large-scale commercialization of Pt alloy catalyst in the future.Secondly,excellent carbon supports were selected for the synthesis of homemade Pt/C catalyst to further improve the stability of Pt/C catalyst.The electrochemical performance(ECSA,ORR),cycle life and stability of HM 70%Pt/C catalyst was better than that of similar international commercial Pt/C catalyst(JM 70%Pt/C).(2)Preparation and experimental test of MEA:Firstly,the preparation method of MEA,assembly method,activation method and test procedure of 25 cm~2 single cell were introduced in detail.Then,HM 70%Pt/C and JM 70%Pt/C catalyst was used to prepare the catalyst layer.The polarization performance and electrochemical impedance spectroscopy(EIS)of 25 cm~2 single cell were measured with 850e fuel cell test system.The peak power density of MEA prepared by HM 70%Pt/C catalyst reached 1.33 W/cm~2,which was significantly higher than that of JM 70%Pt/C catalyst.It is proved that HM 70%Pt/C catalyst can not only show good electrochemical activity in three electrode system,but also show excellent performance in single cell test.(3)Mechanism of PEMFC numerical model:In this chapter,an improved three-dimensional multiphase non-isothermal PEMFC model was established,which considered the agglomeration effect of cathode catalyst layer and oxygen transport resistance.The hydrodynamic model and electrochemical model were coupled.In addition,the hydrogen-crossover induced by ultra-thin proton exchange membrane and the influence of membrane conductivity were also considered.The numerical model mechanism can be used to improve the composition of the catalyst layer and further provide theoretical support for the performance optimization of MEA.(4)Study and optimization of MEA parameters based on numerical model:The calculation model of single channel for PEMFC was firstly established and verified.The results show that the numerical model was in good agreement with the experimental data,and the error was less than 5.0%.The model was used to optimize the performance of the MEA.The optimized parameters include the design parameters of the catalyst layer and the parameters of the proton exchange membrane.The peak power density of the optimized MEA reached 1.59 W/cm~2,which was 19.5%higher than that initial performance.It is proved that the numerical simulation can provide theoretical guidance for the design optimization of MEA.Moreover,numerical simulation can greatly reduce the cost of trial,and create a fast and effective"shortcut"for MEA performance optimization.