Oxygen-reducing biocathodes operating with passive oxygen transfer in microbial fuel cells

Area of Science:

• Electrochemistry
• Environmental Science
• Microbiology

Background:

• Traditional microbial fuel cells (MFCs) with oxygen-reducing biocathodes require energy-intensive catholyte aeration.
• Passive oxygen transfer is a desirable alternative for MFCs to reduce operational costs and complexity.

Purpose of the Study:

• To evaluate the performance of biocathodes using passive oxygen transfer in air cathode MFCs.
• To compare biocathode performance with platinum and non-catalytic cathodes under aerobic conditions.

Main Methods:

• Construction and testing of two-chamber and single-chamber air cathode MFCs.
• Utilizing biocathodes for oxygen reduction in MFCs without active aeration.
• Measuring power density and current density to assess performance.

Main Results:

• Two-chamber air cathode MFCs with biocathodes achieved a maximum power density of 554 mW/m², comparable to Pt cathodes (576 mW/m²).
• Biocathodes in air cathode MFCs reached a maximum current density of 1.0 A/m², outperforming those with aqueous cathodes (0.49 A/m²).
• Single-chamber MFCs showed initial high voltages but biocathode activity was lost due to organic matter exposure, unlike in two-chamber designs.

Conclusions:

• Direct-air biocathodes are effective in MFCs when protected from direct exposure to high organic loads.
• Two-chamber designs effectively maintain biocathode performance by separating it from the anode solution.
• Minimizing heterotrophic microbial growth on the cathode is crucial for sustained biocathode function in air cathode MFCs.