【作者】 张宇；

【导师】 潘牧；

【作者基本信息】 武汉理工大学 ， 材料科学与工程， 2018， 硕士

【摘要】 质子交换膜燃料电池(PEMFC)以其清洁、高效以及广泛应用等优点,几十年来备受关注,但耐久性和可靠性严重制约了其商业化发展。PEMFC在长时间运行中会出现水管理能力下降,严重增加了扩散极化损失,从而严重影响PEMFC的性能。气体扩散层(GDL)在电池水管理中占有重要作用,然而PEMFC的耐久性研究主要集中在膜电极(MEA)中的膜和催化剂上。针对GDL耐久性的研究较少,并且这些报道大多局限在离线加速老化实验。虽然这些研究证实了GDL是造成水管理能力下降的重要原因,但难以反映实际条件下的GDL衰减,也难以得出在线耐久性测试过程中,GDL的衰减老化对电池性能的影响。本文主要针对在线恒电流耐久性测试,GDL衰减对整个MEA的性能影响。分离出了耐久性测试后MEA中的老化GDL,研究实际操作条件下GDL的老化现象,并由极化曲线分析GDL对MEA性能衰减的影响。本论文主要结论如下:1.在线耐久性测试后的MEA能在50 vol%异丙醇水溶液中超声分离出老化的GDL,为单独研究GDL的老化衰减提供了实验基础。在恒电流耐久性测试条件下,MPL(微孔层)腐蚀程度比GDB(基底层,即碳纸)严重,主要体现在碳腐蚀。GDB的腐蚀在700 h耐久性测试后主要是碳腐蚀引起,而在1465 h后则是PTFE的流失。2.GDL的透水性研究表明,MPL侧透水性能强于GDB侧的透水性能。在耐久性测试700 h后,GDL透水性没有发生明显变化,说明其内部疏水性并未发生显著改变;而1465 h的耐久性测试后,阴极MPL的严重腐蚀降低了GDL的透水能力,但阳极GDL的透水性改变不明显,是由于MPL发生腐蚀的同时GDB内部也发生PTFE流失。3.定量分析了GDL对耐久性测试MEA性能的影响。1465 h耐久性测试后的MEA整体性能衰减率为98.98μV/h@800 mA/cm~2,GDL衰减导致的MEA性能的衰减率为13.22μV/h@800 mA/cm~2;GDL老化引起的性能衰减只占整个MEA的13.36%。4.GDL的老化对电池性能影响主要方式是其增加的扩散极化损失而不是欧姆极化损失。MEA在1465 h的耐久性测试后,因GDL的老化衰减增加的扩散极化,引起MEA性能的衰减率为11.37μV/h@800 mA/cm~2。GDL增加的扩散极化对MEA性能的影响占GDL对MEA性能总衰减的86.0%。5.区分了1465 h耐久性测试后CL(CL)和GDL的扩散极化。在耐久性测试后,MEA的总扩散极化由12.81 mV增加到188.05 mV@800 mV/cm~2。而老化的GDL增加的扩散极化损失为18.19 mV@800 mV/cm~2;因此在线恒电流耐久性测试条件下GDL老化增加的扩散极化损失只占MEA总的扩散极化的10.38%。更多还原

【Abstract】 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.更多还原