Determination of Factors Affecting the Performance of Sediment Microbial Fuel Cells by Long-Term Electricity Generation Using Lactic Acid Bacteria-Attached Electrodes

Abstract

Sediment microbial fuel cell (SMFC) performance can be improved using electrodes fermented with and without aeration as cathodes and anodes, respectively. However, this improved performance does not exceed 60 days. In this study, the cathode water-based factors affecting SMFC performance were identified using long-term electricity generation. Meanwhile, SMFC performance (polarization) was measured in experimental conditions. In addition to the polarization measurement, the pH, electrical conductivity (EC) of the cathode water, and adenosine triphosphate (ATP) on the cathode surface were measured. Experiments were conducted with and without the overflow of cathode water. Thereafter, the scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis of the cathodes was performed. In line with existing literature, SMFC performance began to decrease on Day 60 from the commencement of the experiments. Furthermore, the pH difference before and after Day 60 was within 0.2, indicating that the pH of the cathode water did not directly affect SMFC performance. Moreover, EC was kept low with cathode water overflow, significantly decreasing SMFC performance. Further, the SMFC performance increased with an increase in ATP, indicating that the bacterial activities on the electrode affected SMFC performance. The SEM-EDX results revealed that metal ions that were obtained from the dissolution of steelmaking slag attached to the cathode surface, indicating the crystallization of these metal ions during the experiments. These findings indicate that the crystallization on the cathode driven by long-term electricity generation inhibited bacterial activities and cathode reactions, thereby decreasing SMFC performance.