The Study Of Accelerated Degradation Test And Related Factors Of Low Pt Load Electrode

The development of new energy vehicles is an important way to enhance competitiveness of the auto industry,ensure the energy security and develop the low-carbon economy in the world.Proton Exchange Membrane Fuel Cell(PEMFC),which is an efficient energy conversion device,is considered as one of key technologies for the new energy vehicle.Fuel cell vehicle is an important application of fuel call technology.In 2014,a Japanese fuel cell vehicle called Mirai was brought to market and aroused an upsurge for the research and the application of PEMFC.However,high cost and low longevity of the fuel cell vehicle are still two major obstacles to its commercialization.Comparing with foreign countries,there is a big gap on aspect of the platinum loadings and the lifetime of membrane-electrode assemblies(MEAs)in China;and this is one of the urgent problems which need to be solved.This paper starts with membrane-electrode preparation process.The anode platinum loadings of membrane-electrode are fixed at 0.05mgcm-2.Based on the previous work,the processing technology of low platinum loadings of catalyst coated membrane(CCM)and optimum ratios of the catalyst layer components were obtained.When the Nafion content is 1.5 times of the standard content,the optimal initial performance of the CCM with the total platinum loadings of 0.2 mgcm-2(the anode platinum loadings is 0.05 mgcm-2;the cathode platinum loadings is 0.15 mgcm-2)can achieve 440 mWcm-2@0.6 V;and when it is 886 mAcm-2,the power density can be 500.2 mWcm-2 using hydrogen and air as fuel and oxidant under the condition of 0%relative humidity and the temperature of 50?.The optimal initial performance of this CCM can achieve 989 mWcm-2@0.6 V using hydrogen and air as fuel and oxidant under the condition of 90%/70%relative humidity and the temperature of 80?.According to the accelerating degradation test protocol which is recommended by US Department of Energy aiming at the aging of Pt particles,the influence of the platinum loadings and the thickness of proton exchange membrane to the accelerated lifetime of membrane-electrode assemblies were studied based on various analytical way such as the test of the performance and specific electrochemical surface area of MEAs,the SEM study of the surface and the cross-section of the catalyst layer of MEAs,associated with back scattered electron imaging(BSE),EDX mapping,EDX linear scan techniques..The accelerating test for different cathode platinum loadings of CCM MEAs show that the voltage drop at 800 mAcm-2 is about 71.7 mV 145,7 mV,230.5 mV for the MEAs with cathode Pt loading of 0.55,0.15,0.05 mgcm-2 respectively.The decline of the cathode platinum loadings leads to the increase of' the voltage degradation of the membrane-electrode assemblies.The accelerating test of the CCM MEAs with 0.2 mgcm-2 total platinum loadings made from different proton exchange membranes show that the membrane can affect the lifetime of the MEAs too.The voltage drop at 800 mAcm-2 is about 58.3 mV,145.7 mV,59.3mV for the MEAs with NR212(50?m),XL(30?m)and HP(20?m)membrane respectively.The thinner membrane with similar structure of HP and XL is in favor of improving the lifetime of the MEAs.The spatial distribution of aggregated Pt particles at cathode of our self-made MEAs was revealed for the first time by analyzing the microstructure,the elements content and distribution of the catalyst layer of the MEAs.It suggested more Pt accumulation at the interface between the membrane and the catalyst layer.This implies the different spatial utilization of the Pt catalyst in the catalyst layer.This result points out the further direction for improving the longevity of the membrane-electrode assemblies.