Microbial electrolysis cell with a microbial biocathode.

Area of Science:

• Microbial Electrochemistry
• Bioelectrochemical Systems
• Renewable Energy Technologies

Background:

• Traditional microbial electrochemical cells (MECs) often rely on expensive noble metal catalysts like platinum for reactions.
• Developing cost-effective and sustainable alternatives for catalysis in MECs is crucial for their practical application.

Purpose of the Study:

• To demonstrate the proof-of-principle for a novel MEC design utilizing microbial catalysis for both anodic and cathodic reactions.
• To evaluate the performance and hydrogen production efficiency of such a bio-electrochemical system.

Main Methods:

• Construction and simultaneous operation of two MECs with microbial catalysts on both electrodes.
• Performance testing including current density measurements at a specific applied cell voltage and cathode potential.
• Comparison of biocathode performance against a control cathode without microbial activity.
• Assessment of cathodic hydrogen recovery and identification of hydrogen loss pathways.

Main Results:

• The MECs achieved a maximum current density of 1.4 A/m² at 0.5 V applied cell voltage.
• The biocathode exhibited significantly higher current densities (1.9–3.3 A/m²) compared to the control cathode (0.3 A/m²), indicating microbial catalysis of hydrogen production.
• Cathodic hydrogen recovery ranged from 17% to 21%, with losses attributed to diffusion and methane formation.
• Long-term operation (1600 h) showed a decrease in current density to 0.6 A/m², likely due to calcium phosphate precipitation on the biocathode.

Conclusions:

• The study successfully demonstrated a MEC functioning with microbial catalysis on both electrodes, offering a platinum-free alternative.
• Microbial electrocatalysis at the biocathode is effective for hydrogen production, though subject to losses.
• Long-term stability challenges, such as calcium phosphate precipitation, need further investigation for practical MEC development.