Micro/Nano Technologies for Achieving Sustainable Microbial Electrochemical Cell Systems

Abstract

Microbial electrochemical cell systems (MECSs), such as microbial fuel cells (MFCs) and microbial electrolysis cells (MECs), are promising clean and renewable energy sources. MFCs employ exoelectrogenic bacteria to convert organic matter in wastewater into electricity, and biogas (hydrogen, methane) is generated from organic matter by applying electricity in MECs. This emerging technology requires better performance by decreasing the material cost to bring it into practical application. Therefore, the main focuses of this research are fabricating nanomaterial based anode to improve the power production and developing micro devices to analyze real-time performance of MECSs.

Physical and electrochemical interactions between microbes and anode are critical to performance. Systematic studies on how different lengths, packing densities, and surface conditions of carbon nanotubes (CNTs) affect MFC power output revealed that long and loosely packed CNTs without any amorphous carbon show the highest power production performance. Furthermore, fabricated 3D sponges composed of interconnected CNTs showed better performance compared to commercially available carbon felt anode.

Due to the configuration, monitoring of biofilm development is hard in macro-sized MFCs. Microfluidic laminar flow MFC with interdigitated anode was fabricated to monitor the real-time optical and electrochemical activity of Shewanella oneidensis MR-1 in situ. Power density and impedance were measured to understand the relation between biofilm development and power production of biofilm over time.

Expensive and labor intensive equipment such as gas chromatography is commonly used to analyze the biogas produced in MECs. A ZnO nanowires based gas sensor was fabricated to measure H2 concentration in real-time without using any other expensive equipment.

Low power and low voltage output of MFCs do not allow them to power most electrical applications. Proposed power management systems (PMSs) can overcome this limitation by boosting the MFC output voltage and managing the power for maximum efficiency, regardless of the power and voltage fluctuations from MFCs over time.

Overall, the limitations of the MECSs technology have been identified and possible solutions have been proposed to improve the overall performance of this sustainable renewable energy source.