Improving phosphate buffer-free cathode performance of microbial fuel cell based on biological nitrification

Area of Science:

• Environmental Science
• Electrochemistry
• Microbiology

Background:

• Phosphate buffers are commonly used in microbial fuel cells (MFCs) but contribute to operational costs and environmental concerns.
• Reducing buffer reliance is crucial for sustainable and cost-effective MFC technology.

Purpose of the Study:

• To investigate the feasibility of using biological nitrification to replace phosphate buffers in MFC cathodes.
• To evaluate the impact of nitrification on MFC performance, including voltage, power output, and cathode polarization resistance.

Main Methods:

• Inoculating the cathode compartment with a nitrifying mixed consortia (NMC).
• Increasing ammonium concentration in the catholyte.
• Monitoring cell voltage, pH, nitrate-nitrogen levels, and power generation.
• Measuring polarization resistance to assess cathode performance.

Main Results:

• Addition of NMC and ammonium increased cell voltage from 0.3 V to 0.567 V and decreased catholyte pH from 8.8 to 7.05.
• Significant ammonium oxidation to nitrite was observed, indicated by increased nitrate-nitrogen.
• The MFC with NMC achieved a maximum power density of 10.94 W/m(3), outperforming buffered and non-buffered controls.
• The buffer-free NMC-inoculated cathode exhibited the lowest polarization resistance, indicating improved cathode efficiency.

Conclusions:

• Biological nitrification effectively replaces phosphate buffers in MFCs, enhancing overall cell performance.
• Nitrification improves cathode kinetics, likely due to proton production facilitating oxygen reduction.
• This approach offers a sustainable and efficient alternative for MFC operation.