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Less is More: A Comprehensive Study on the Effects of the Number of Gas Diffusion Layers on Air–Cathode Microbial Fuel Cells
ChemElectroChem ( IF 3.5 ) Pub Date : 2021-08-14 , DOI: 10.1002/celc.202100908
Pilar Sánchez-Peña 1 , Jesús Rodriguez 2 , Raquel Montes 1 , Juan Antonio Baeza 3 , David Gabriel 1 , Mireia Baeza 4 , Albert Guisasola 5
Affiliation  

Air-cathode microbial fuel cells (AC-MFC) use a gas-diffusion-layer (GDL) coating based on polytetrafluoroethylene applied to the cathode to prevent electrolyte leakage. However, this type of GDL can also lead to a decrease in MFC performance due to electron-transfer limitation, mass-transfer limitation or catalyst availability. This study provides a comprehensive understanding of the significance of the GDL coating, demonstrating the interaction between the number of GDL coatings and the external resistance (Rext) used. An experimental design in 28 mL AC-MFCs was prepared and conducted using two different Rext (10 and 249 Ω) and four different GDL coatings (1 to 4 layers). The coating effect was not significant when operating with a high Rext, where the electron transfer was the limiting process. However, when the Rext was low, the amount of polytetrafluoroethylene limited the cathode performance due to a significant decrease in the Pt availability on the catalytic surface. Thus, GDL-1 with 10 Ω as Rext reached 0.96 mA/cm2, 3-fold higher than that obtained with 249 Ω as Rext (ca. 0.30 mA/cm2). Besides, the current density did not vary noticeably in the other cathodes with 249 Ω as Rext. Contrarily, the current density with 10 Ω as Rext decreased as the number of GDL increased (0.74, 0.57 and 0.37 for GDL-2, GDL-3 and GDL-4 respectively). These values agreed with those of the polarization curve. Furthermore, limitations were also observed in electrochemical impedance spectroscopy measurements: the charge resistance increased with the number of GDL, related to the ease of electron flow. These values were18 Ω, 22 Ω, 53 Ω and 58 Ω for GDL-1, GDL-2, GDL-3 and GDL-4, respectively, for both 10 and 249 Ω cathodes.

中文翻译:

少即是多:气体扩散层数量对空气-阴极微生物燃料电池影响的综合研究

空气阴极微生物燃料电池 (AC-MFC) 使用基于聚四氟乙烯的气体扩散层 (GDL) 涂层应用于阴极,以防止电解质泄漏。然而,由于电子转移限制、传质限制或催化剂可用性,这种类型的 GDL 也可能导致 MFC 性能下降。这项研究提供了对 GDL 涂层重要性的全面理解,证明了 GDL 涂层的数量与所使用的外部电阻 (R ext )之间的相互作用。使用两种不同的 R ext(10 和 249 Ω)和四种不同的 GDL 涂层(1 到 4 层)准备并进行了 28 mL AC-MFC 中的实验设计。以高 R ext操作时,涂层效果不显着,其中电子转移是限制过程。然而,当 R ext较低时,聚四氟乙烯的用量会由于催化表面 Pt 可用性的显着降低而限制了阴极性能。因此,具有 10 Ω 作为 R ext 的GDL-1达到了 0.96 mA/cm 2,比使用 249 Ω 作为 R ext(大约 0.30 mA/cm 2)获得的GDL-1高 3 倍。此外,电流密度在其他阴极中没有明显变化,R ext为 249 Ω 。相反,电流密度以 10 Ω 作为 R ext随着 GDL 数量的增加而降低(GDL-2、GDL-3 和 GDL-4 分别为 0.74、0.57 和 0.37)。这些值与极化曲线的值一致。此外,在电化学阻抗谱测量中也观察到了局限性:电荷电阻随着 GDL 的数量而增加,这与电子流动的容易程度有关。对于 10 Ω 和 249 Ω 阴极,GDL-1、GDL-2、GDL-3 和 GDL-4 的这些值分别为 18 Ω、22 Ω、53 Ω 和 58 Ω。
更新日期:2021-09-09
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