Research On The Durability Of Proton Exchange Membrane Fuel Cell Stack Based On The Design Of Accelerated Cycles

As a vehicle power source,proton exchange membrane fuel cell is one of the most promising new energy technologies and its durability restricts its large-scale application.The durability of proton exchange membrane fuel cells is one of the most important issues in recent years and accelerated stress testing is one of the most common and effective techniques to study the durability of proton exchange membrane fuel cells.Therefore,this thesis focuses on the test and simulation of the durability of the proton exchange membrane fuel cell stack based on designing different acceleration cycles.First,based on the operating data of the proton exchange membrane fuel cell bus,a baseline cycle is established,which is performed in a durability test on a 3k W12-cell fuel cell stack.After 150 cycles,the degradation percentage of the fuel cell stack is 1.42%,and the degradation rate is 6.45×10^-4V/h.In this thesis,the change of operating conditions,voltage response,polarization curves and uniformity of the stack are analyzed in detail.The results show that the performance and uniformity of the fuel cell stack degrade greatly in the first 50 cycles and slow down in the last 100cycles.The poor performance of the single cell is the main reason for the decrease in uniformity.In addition,according to the electrochemical characterization results,the middle area as well as the hydrogen inlet area of the membrane electrode have less degradation,while the hydrogen outlet area has a significant degradation.Secondly,different acceleration cycles are designed for fuel cell stack durability test in order to study the effects of different acceleration cycles on the degradation of fuel cell stacks.After 1000 cycles of No.1 acceleration cycle,the performance degradation percentage of the fuel cell stack is 2.71%,and the performance degradation rate is 1.79×10^-4V/h.At 150 cycles,the fuel cell stack under the acceleration cycle durability test degraded much more than that under the baseline cycle durability test.The fuel cell stack degrades fast before 250 cycles,but degrades little after 250 cycles.By analyzing the experimental data,it is found that the high humidity reduces the voltage drop of the fuel cell stack during the loading process,which helps to propose effective aging mitigation strategies of the fuel cell stack.Intermittent test led to voltage recovery of fuel cell stack.The durability test of No.2acceleration cycle test and No.3 acceleration cycle test are carried out for 100h respectively.Comparing the degradation performance percentage and performance degradation rate of No.1 acceleration cycle test in 900-1000h,No.2 acceleration cycle and No.3 acceleration cycle accelerate fuel cell stack degradation.Increasing the loading rate of the fuel cell stack from 25A/s to 50A/s is abel to accelerate the degradation of the fuel cell stack,but the magnitude is not massive.Finally,a 2D fuel cell stack degradation model is established by combining the experimental data and simulation,which mainly considers two degradation mechanisms:platinum particle dissolution and proton exchange membrane degradation.The simulation results show good agreement with the test data and the reduction of active specific surface area is the most important factor for fuel cell stack degradation and the fuel cell stack fails after 4200 cycles of No.1 acceleration cycle.In addition,the degradation performance of fuel cell stack under different cycles is simulated,with 2D fuel cell stack degradation model.It is shown that the simulation results are in good agreement with the experiment data,which proves that the degradation model is able to simulate the degradation performance of fuel cell stack under different cycles.