Correlation of Overvoltages and Current Densities to Estimate Optimal Electrode Size for Sediment Microbial Fuel Cells

Abstract

We propose a method to determine the optimal electrode size of sediment microbial fuel cells (SMFCs). Four SMFCs presented a proportional increase in the current to the electrode size of the MFCs at day16. From the I-V curves of the SMFCs, four plots of current versus electrode size (I-E-size plots) were obtained, which displayed high R-2 values ranging from 0.980 to 0.994. At day47, however, V-I curves deviated in one of the four MFCs, such that the I-E-size plots obtained from the I-V curves were inappropriate for estimating the electrode size. We found that the curves of overvoltage against the current density (-j curves) were comparable in the SMFCs, suggesting that the overvoltage is inversely proportional to the electrode size of the MFCs. The I-E-size plots corrected by using the -j curves had high R-2 values of over 0.978, indicating that the -j curves can be used for estimating the electrode size when the working voltage to current density ratio is different in SMFCs.