A Systematic Study of Separators in Air-Breathing Flat-Plate Microbial Fuel Cells—Part 1: Structure, Properties, and Performance Correlations

Abstract

Passive air-breathing microbial fuel cells (MFCs) are a promising technology for energy recovery from wastewater and their performance is highly dependent on characteristics of the separator that isolates the anaerobic anode from the air-breathing cathode. The goal of the present work is to systematically study the separator characteristics and its effect on the performance of passive air-breathing flat-plate MFCs (FPMFCs). This was performed through characterization of structure, properties, and performance correlations of eight separators in Part 1 of this work. Eight commercial separators were characterized, in non-inoculated and inoculated setups, and were examined in passive air-breathing FPMFCs with different electrode spacing. The results showed a decrease in the peak power density as the oxygen and ethanol mass transfer coefficients in the separators increased, due to the increase of mixed potentials especially at smaller electrode spacing. Increasing the electrode spacing was therefore desirable for the application of diaphragms. The highest peak power density was measured using Nafion ® 117 with minimal electrode spacing, whereas using Nafion ® 117 or Celgard ® with larger electrode spacing resulted in similar peak powers. Part 2 of this work focuses on numerical modelling of the FPMFCs based on mixed potential theory, implementing the experimental data from Part 1.

Microbial fuel cell review: thermodynamic and infuencing factors, exoelectrogenic bacteria, anode and cathode configuration

“…Figure 15 shows examples of one-compartment MFCs. 78,79 Figure 13(c) Separator/electrode assembly 72 the electrolytes employed in MFCs have low conductivity, lowering the interelectrode spacing may result in lower internal resistance of batteries. 16 Bringing the electrodes too close together may result in oxygen diffusion at the anode, thus limiting the growth of bacteria that create electricity and possibly causing short circuits.…”

“…The concentration of substrate also affects MFC performance, in addition to the substrate itself. A saturation-type relationship has been observed between the power generated and the amount of substrate originally fed to the reactor; 79 Cheng and Logan demonstrated that this parameter remarkably affected the anode's performance. 79 The findings of Khaled are summarized in Fig.…”

“…23). 18,79 This result is a direct outcome of a reduction in the MFC's internal resistance, particularly its ohmic resistance, expressed as…”

Soft Materials for Wearable/Flexible Electrochemical Energy Conversion, Storage, and Biosensor Devices

“…The authors also designed a novel arrangement by totally replacing cathode graphite plates with a light (0.065 g), flexible, and cheap plastic membrane obtaining higher energy density than conventional PEMFCs. In the cathode design, they used the air-breathing concept (Figure 1), introduced in 2013 [92], and afterwards, intensely developed to make PEMFCs suitable to wearable devices [93]. Another important issue of this topic covers the choice of suitable oxygen reduction reaction (ORR) electrocatalysts, which are known to be key materials for efficient and highly performant PEM and Zn-airFC devices [82,84,94].…”

“…Exploded view of fuel cell components in an air-breathing configuration. Reproduced from reference[93] under CC BY 4.0 license.…”