Study On Durability Of Gas Diffusion Layers In The Proton Exchange Membrane Fuel Cells

Membrane Fuel Cell(PEMFC)has been paid much attention because of its property of environment friendly,efficient and widely use.However,the durability and realiability hinder its commercialization.The decrease of water management in the operation of PEMFC will cause the increase of the mass transport loss,thus lead to a lower performance.At the meantime,gas diffusion layer(GDL)plays an important role to the water management of fuel cell.Nowdays,researches on durality of PEMFC focus on the membrane and catalyst.A few researches have reported that GDL would lower the water management using ex-situ accelerated aging experinment which could not reflect recession on actual operating conditions and the relationship between aging of GDL and performance of fuel cell.In this paper,the effect on performance of fuel cell caused by the decay of GDL after constant current durability online test has been studied.The aged GDL was separated from the aged MEA after durability test to study the decay on the actual operation.Furthermore,the impact of GDL on the performance of MEA had been studied by analyzing I-V curve(polarization curve).Below conclusions of this paper could be drawn:1.The aged GDL could be completely separated from the MEA by ultrasonic treatment of 50 vol%isopropanol aqueous solution after durability test which provides the experimental material basis for distinguishing the effects of GDL from the MEA.For the actual durality,the decay of MPL which was mainly caused by carbon corrosion was much more serious than the GDB.The aging of GDB on PEMFC for testing 700 h was resulting from the carbon corrison whereas the 1465 h was the loss of PTFE.2.Study on the water permeability of MPL and GDB showed that the water permeability of MPL side was larger than the GDB side.After 700 h durability test,there was fewer change on the water permeability of GDL which indicated that the internal hydrophobic of GDL almost unchanged.For 1465 h testing,the serious corrosion of cathode MPL reduced the water permeablity of GDL,while the anode MPL was not unapparent resulted from the synergistic effect of the corrison of MPL and loss of PTFE in the GDB.3.Quantificational analysis of the effect of GDL on the MEA performance indicated that the loss of performace of MEA(98.98μV/h)caused by the decay of GDL(13.22μV/h)was 13.36%under a current density of 800 mA/cm~2.4.The aging of GDL affected the performance of MEA resulted primary in the mass transport loss rather than the ohmic polarization loss.After testing for 1465 h,the aging of GDL led to an increase of mass transport,and the performance loss of MEA caused by the increase of mass transport was 11.37μV/h@800 mA/cm~2 which accounted for 86.0%to that of GDL.5.The mass transport loss of the GDL and catalyst layer(CL)was distinguished.The diffusion polarization loss of MEA increased from 12.81 mV to 188.05 mV@800mA/cm~2 after 1465 h durability test.Where the increase of the mass transport loss caused by GDL was 18.19 mV@800 mA/cm~2,accounted for 10.38%to that of MEA.