Hydrogen production using single-chamber membrane-free microbial electrolysis cells.

Area of Science:

• Energy science
• Microbiology
• Electrochemistry

Background:

• Microbial electrohydrogenesis is a promising method for sustainable hydrogen generation.
• Conventional microbial electrolysis cells (MECs) utilize membranes, which can lead to energy losses.
• Developing membrane-free MECs is crucial for improving energy recovery and efficiency.

Purpose of the Study:

• To investigate hydrogen production using single-chamber, membrane-free microbial electrolysis cells (MECs).
• To evaluate the performance of both a mixed microbial culture and the pure culture Shewanella oneidensis MR-1.
• To assess the impact of methane production and explore methods for its suppression.

Main Methods:

• Design and implementation of a single-chamber, membrane-free MEC.
• Cultivation and testing of a mixed microbial consortium and Shewanella oneidensis MR-1 for hydrogen production.
• Analysis of hydrogen production rates, current densities, and the influence of pH.
• Investigation of methane production and its mitigation strategies, such as cathode air exposure.

Main Results:

• The membrane-free MEC achieved significant hydrogen production rates with a mixed culture (0.53 m(3)/day/m(3) at pH 7 and 0.69 m(3)/day/m(3) at pH 5.8) and high current densities.
• Stable hydrogen production was observed using Shewanella oneidensis MR-1 with lactic acid as a substrate.
• Methane production was detected with the mixed culture, reducing hydrogen yield, but could be suppressed by exposing cathodes to air.
• Potential for further increases in current density and hydrogen production rate through electrode optimization.

Conclusions:

• Single-chamber, membrane-free MECs are effective for hydrogen production from biomass.
• Shewanella oneidensis MR-1 demonstrates stable hydrogen production capabilities.
• Controlling methanogenesis is key to maximizing hydrogen yield in mixed cultures.
• Further optimization of electrode configuration can significantly enhance MEC performance.