Study On Low-Pt Membrane Electrode Assembly Prepared By Magnetron Sputtering On Gas Diffusion Layers

Proton Exchange Membrane Fuel Cell?PEMFC?as a new generation of power generation technology had attracted worldwide attention on account of its broad application.But the two key technical issues of cost and lifetime had also restricted the PEMFC`s commercial development.However,the cost problem mainly lies in the fact that the membrane electrode assembly?MEA?which is the core of PEMFC used a large amount of precious metal Pt as the catalyst.How to reduce the Pt loading and meanwhile ensure the high power density of the MEA had become a major technical bottleneck that needs to be broken.So far,there were mainly two methods to reduce the Pt loading,such as Pt-alloy catalyst and non-Pt catalyst.However,the former catalyst was easy to cause Pt agglomeration due to its structure`s instability.The latter's catalytic performance was not enough to meet the requirements of battery operation.Magnetron sputtering technology can achieve the target of ultra-low Pt loading MEA,beacause the loading of Pt prepared by magnetron sputtering was controllable,and the Pt particles were evenly distributed.Therefore,magnetron sputtering was one of the most important technical approaches to achieve the target of high power density and low Pt loading membrane electrodes assembly.The main work of this paper was to sputter Pt on the surface of Micro Porous Layer?MPL?with texture structure and prepare MEA for single cell performance test.The following conclusions were obtained through a series of experiments such as sputtering parameters,sputtering Pt loading,sprayed Nafion loading and MPL morphology optimization.1.Through the sputtering Pt parameters optimization experiment and the analysis of the test data,it could be concluded that the Pt`s catalytic performance was best when the sputtering pressure and sputtering power were 6 Pa and 100 W,respectively.And Pt`s electrochemical active area?ECSA?and specific activity?SA?could reach the highest values 22.8 m²/g and 953.3?A/cm²,respectively.2.By sputtering different loadings of Pt on commercial GDL and single cell test,it was proved that the maximum power density of single cells could reach 0.54 W/cm²in the condition of 0.04 mg/cm² Pt loading.The mass specific power of Pt was also as high as 13.5 W/mg.Below the Pt loading of 0.04 mg/cm²,the performance of the single cell was too low to meet the performance requirements of the normal operation of the battery.Above this loading,the target of reducing Pt loading couldn`t be achieved due to the low utilization rate of Pt.So 0.04 mg/cm² was selected as the optimum sputtering Pt loading.3.By spraying different loadings of Nafion on a commercial GDL which was sputtered 0.12 mg/cm² Pt and the single cell test,it was concluded that the single cell could reach the maximum power at a Nafion loading of 0.2 mg/cm².The power density,internal resistance,and ECSA of the MEA all reached the optimum values of 0.95W/cm²,5 m?,and 62 cm²/mg,respectively.4.The textured GDL was prepared by using a mesh printing method to form a textured MPL on the surface of the carbon paper.Scanning electron microscope?SEM?and profiler were used to prove that the roughness of the textured MPL was indeed higher than that of the commercial MPL.The maximum power density of the single cells using the textured GDLs as the sputter substrate could reach 1.05W/cm²@0.04mg/cm²_Pt and 1.1 W/cm²@0.24mg/cm²_Pt which were higher than the sing cells prepared by the comercial GDLs.However,in the case of low Pt loading,the performance of a single cell prepared by a textured GDL was superior to that of a standard Pt/C,but the performance was slightly lower in the case of a high Pt loading.