A 4-Electrode Microfluidic Microbial Fuel Cell Doubles Power Output and Conversion Efficiency, but Gravitational Effects must Be Overcome

Abstract

High-power output and high conversion efficiency are crucial in the study of microfluidic microbial fuel cells (MFCs). In our previous work, we attempted various methods to increase the power density of the MFCs, but nutrient consumption was limited to the bottom (electrode) layer of the microfluidic channel due to the diffusion limitations. In this work, long-term experiments were conducted on a new 4-electrode microfluidic MFC design, which grew Geobacter sulfurreducens biofilms on upward- and downward-facing electrodes in the microchannel. It was discovered that inoculation and growth of the electroactive biofilm did not proceed as fast as the downward facing anode, which we hypothesize is due to gravity effects that negatively impacted bacterial settling on that surface. Rotating the device during the growth phase resulted in uniform and strong outputs from both sides, yielding individual power densities of 4.03 and 4.13 W m⁻², which was increased to nearly double when the top- and bottom-side electrodes were operated in parallel as a single 4-electrode MFC. Similarly, acetate consumption could be doubled with the 4-electrodes operated in parallel.

Key findings

• ▸The 4-electrode design allowed for uniform growth of electroactive biofilms on both upward- and downward-facing electrodes.
• ▸Gravity effects negatively impacted bacterial settling on downward-facing electrodes, but rotating the device during growth phase improved results.
• ▸Operating top- and bottom-side electrodes in parallel as a single 4-electrode MFC nearly doubled power density and acetate consumption.

Keywords

Identifiers

DOI

10.20944/preprints202407.0531.v1

Journal

Preprints.org

Year

2024