500hr加速耐久性测试燃料电池失效初步分析：失效节位置、膜电极失效位置、内阻、催化剂粒径、电化学表面积、开路电压、亲疏水性规律

Analysis on the PEM fuel cells afteraccelerated life experiment

Pucheng Pei

Xing Yuan

Pengxiang Chao

Xizhong Wang

Abstract

After 500h accelerated lifetime test on an automotive PEM （proton exchange membrane）fuel cell stack， the performance of thecells at the stack＇s foreside is the worst． The electrochemical surfacearea， internal resistance， particle size and hydrophobic nature of catalyst are measured based on theelectrochemical methods， electronic－lens and dropped water test． Theresults show that the internalresistance increases to double and theaverage particle diameter increases to 3 times when electrochemically activearea surface coefficient decreases to one－fifth． The open circle voltage of the worst cell is 0．7 V and its maximumcurrent density is 200 mA／cm2． Especially， theperformance of part at air－outlet is the worst， followed by the part atair－inlet， hydrogen－outlet， and hydrogen－inlet．

从数据上看最糟糕的是两大出口。

The phenomenon mentioned above at the inlet of stack is the most seriousamong all the cells in the stack．

没有提供电堆来源、操作条件、布置方式、电堆节数和进出气位置关系（只在摘要中提到第1节是电堆入口侧）。

Fig． 1 – （a） Polarization curve characteristics  of No．1–14 cells and No．15–100 cells in a stack． （b） Cell voltages of stack after  500 h working comparing with new stack on the same load．

Fig． 2 – Five small sections have been  taken from stack MEA： hydrogen－inlet part， hydrogen－outlet part， air－inlet part，  air－outlet part and the middle part．

Fig． 3 – Polarization curve of small  cells in different part of primary stack cells． （a） No．1 cell． （b） No．4 cell．  （c） No．8 cell．

Fig． 4 – Results comparison of all parts  in every cell． （a） Electrochemically active surface area coefficient． （b）  Average particle diameter values． （c） Contact angle values． （d） Impedance  values．

Table 1 – Standard deviations of average  particle diameter．

Conclusions

After an accelerated lifetime test，  catalyzes on the MEA agglomerate to some degree． The average particle  diameter grows bigger and internal resistance increases while hydrophobic nature remains the same．

In addition， the catalyzes electrochemically  active surface area coefficient increases这句话写的有些问题， oppositely  the maximum of loading current decreases．

There are enormous differences on  performance degradation among different flow field positions and among  different cells． Open circuit  potential of the worst position is 0．7 V while

the  best one is 0．96 V． Maximum of current density of  the worst position is 200 mA／cm2 ， which is one－sixth of the best one．

Electrochemically active surface area  coefficient of the worst position is 25， which is less than one－fifth of the  best one．

Average particle diameter of the worst  position is 21 nm， which is 2 times bigger than the best one．

Impedance of the worst position is 250 毫欧cm2 ， which is twice of the best one．

But contact angle of the worst position  and the best one does not differ by more than 10％．

The best performance of fuel cell is the  hydrogen－inlet part， while the worst part is air－outlet part．

This may be caused by frequent air  starvation or flooding in the air－outlet．

The performance of first cell is the worst  and that of eighth cell is the best．

The probable reason is Non－uniform gas  intake and water distribution．

最后的推测纯粹为推测，没有仿真和表征数据支持。