Subject Area物理化学
Progress in PFMFC Durability Study at DICP
Shao ZG(邵志刚); Yu HM(俞红梅); Hou M(侯明); Li XJ(李晓锦); Zhou L(周利); Yi BL(衣宝廉)
Conference Date2010-7-11
Conference Place中国
Funding Organization上海交通大学
AbstractIn this paper, the recent progresses in the study of PEMFC durability in DICP are reviewed. Compared to static loading, dynamic loading can accelerate the degradation of fuel cells. The details were studied by setting voltage or temperature sensors inside the fuel cell under both steady and transient states. Results show that under transient state, the fuel cell would experience a temporary voltage fluctuation due to the air starvation. Thus could probably lead to the degradation of materials, such as the catalyst, membrane, etc. To lessen the degree of air starvation, a method of pre-supplying certain amount of air before loading was adopted. The temperature fluctuations in different zones are also observed. When the air stoichiometry is very low, the temperature near the cathode inlet increases dramatically, which may result from the current rising. The extent of temperature change inside fuel cell under dynamic running can be reduced by increasing air stoichiometry. The fuel starvation also causes irreversible damages to PEMFC, especially in stacks. The phenomenon was investigated experimentally with a specially constructed segmented fuel cell. Experimental results show that during the cell reversal process due to the fuel starvation, the current distribution is extremely uneven, the local high interfacial potential is suffered near the anode outlet, hydrogen and water are oxidized simultaneously in the different regions at the anode, and the carbon corrosion is proved to occur at the anode by analyzing the anode exhaust gas. When the fuel starvation becomes severer, the water electrolysis current gets larger, the local interfacial potential turns higher, and the carbon corrosion near the anode outlet gets more significant. Improper start-up and shutdown processes induce high interfacial potential which can corrode electrodes. Those potential differences were investigated by setting a home-made dynamic hydrogen energy into MEA. For unprotected start-up process, as hydrogen was introduced from anode inlet, the potential of membrane inlet increased, and the potential of membrane outlet decreased, creating a very large potential difference between membrane inlet and outlet. It was measured to be as high as 0.8 V, and the cathode interfacial potential could reach about 1.6 V. Such high interfacial potential difference could corrode the carbon in catalyst layer, accelerate platinum dissolution and make great damage to fuel cell. For unprotected shutdown process, as air would diffuse into anode. During the formation of hydrogen/air boundary, the interfacial potential difference between cathode and membrane outlet also increased dramatically to be almost 1.6 V, causing significant carbon corrosion. It was found that purge with nitrogen during start-up and application of dummy load during shutdown was very effective to avoid the formation of hydrogen/air boundary and reduce the damage to fuel cell. Cold start is another factor effecting the lifetime of PEMFC. The hydrophilic nano oxide such as SiO2 is added into the catalyst layer (CL) of the cathode to improve the cold start performance. The effect of hydrophilic nanosized SiO2 addition in the cathode CL on PEMFC is investigated by comparative study of 8 cold start cycles at different current densities and temperatures. The cell with 5 wt. % nanosized SiO2 in the cathode catalyst layer is able to self-startup from -8°C at 50 mAcm-2, but the one with no nanosized SiO2 fails. In addition, the cell with 5 wt. % nanosized SiO2 shows longer life time at -10°C than the one with no SiO2.
Document Type会议论文
Corresponding AuthorShao ZG(邵志刚)
Recommended Citation
GB/T 7714
Shao ZG,Yu HM,Hou M,et al. Progress in PFMFC Durability Study at DICP[C],2010:72/2.
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