气体扩散层的裂缝对燃料电池性能的影响和配合流道尺寸的作用因素

Impact of cracked gas diffusion layer onperformance of polymer electrolyte membrane fuel cells

Geon Hwi Kim

Dasol Kim

Jaeyeon Kim

Hyeok Kim

Taehyun Park

Abstract

This paper reports the negative effect ofthe cracked gas diffusion layer （GDL） on the performance of polymer electrolytemembrane fuel cells （PEMFCs） undervarying flow channel width． The polarization characteristics and thecorresponding electrochemical impedance spectra of the PEMFCs with pristineGDLs and cracked GDLs were computed． The results showed that for PEMFCs with 1．0 mm flow channels， the power densityrates of reduction between the PEMFCs with pristine GDLs and those with crackedGDLs were 2．8％ under the condition of oxygen and 6．6％ under the condition ofair． On the other hand， for the PEMFCs with0．5 mm flow channels， these values were 10．3％ under the oxygen condition and14．2％ under the air condition． This implies that the thinner the flow channels，the more severely the cracked GDLs influence the PEMFC performance in terms ofconcentration loss． The EIS data indicated that， compared to the PEMFCs with1．0 mm flow channels， the cracks on GDLs had more impact on the PEMFCs with 0．5mm flow channels with regard toactivation overvoltage．

Fig． 1． Schematic of graphite bipolar  plates， Pt／C layer， and proton－exchange membrane． The two digital camera  images at the center indicate the pristine and cracked GDLs．

Fig． 2． Digital camera images of （a）  cracked GDL after artificial bending and （b） a comparison of pristine and  cracked GDLs．

Fig． 3． Graphite bipolar plate of （a） 1．0  mm and （b） 0．5 mm flow channels．

Fig． 4． O2 and air cathode polarization  j–V curve of （a） 1．0 mm and （b） 0．5 mm flow channels．

Fig． 5． O2 and air cathode polarization  j–P curve of （a） 1．0 mm and （b） 0．5 mm flow channels

Table 1 Power density and corresponding  rate of reduction between the PEMFCs assembled with pristine GDLs and those  assembled with cracked GDLs．

Fig． 6． Nyquist plot at 0．85 V cell voltage  of （a） 1．0 mm and （b） 0．5 mm flow channels．

Conclusion

In this study， the polarization curves  and EIS data were tracked with regard to PEMFCs with 1．0 mm and 0．5 mm flow  channels， which were assembled with pristine 39BC GDLs and cracked 39BC GDLs， respectsively．

The j–V polarization curve  characteristics and the corresponding EIS were analyzed on the basis of the experimental  results． The power density rates of reduction for the PEMFCs with 1．0 mm flow  channels were 2．8％ and 6．6％ under the conditions of oxygen and air， respectively．  In addition， the rates for the PEMFCs with 0．5 mm flow channels were 10．3％  and 14．2％ under the conditions of oxygen and air， respectively． Compared to the  PEMFCs with 1．0 mm flow channels， the power density rates of reduction were  higher for PEMFCs with 0．5 mm flow channels．

Thus， it is speculated that the cracks on  GDLs cause more damage to the PEMFC performance if the flow channels become  thin．

Furthermore， the EIS data indicates that  the gaps of activation overvoltage between the PEMFCs with pristine GDLs and  those with cracked GDLs can increase if the flow channels become thin．

Finally， the cracks on the GDLs might  induce more concentration losses for the PEMFCs with 0．5 mm flow channels  than for those with 1．0 mm flow channels． There were some inconsistent tendencies  between the PEMFCs with 1．0 mm flow channels and those with 0．5 mm flow  channels．

In the future， additional investigation，  including cracking of GDLs through a machine to inflict equal cracks and  conducting experiments with thinner or  thicker flow channels to identify more tendencies， seems to be required  to gain a better understanding of PEMFCs．

这篇文章有些不解渴。

是否其他类型的气体扩散层也会有同样的趋势？

不同的气体扩散层是否有的影响大，有的影响小？

不同厚度的气体扩散层是否有的影响大，有的影响小？

单纯阳极气体扩散层缺陷和单纯阴极气体扩散层缺陷的结果如何？

气体扩散层的缺陷范围多大对结果有影响？相互关联是什么？影响活化过电位的原因是什么？