Impact of initial biofilm growth on the anode impedance of microbial fuel cells

Abstract

Electrochemical impedance spectroscopy (EIS) was used to study the behavior of a microbial fuel cell (MFC) during initial biofilm growth in an acetate-fed, two-chamber MFC system with ferricyanide in the cathode. EIS experiments were performed both on the full cell (between cathode and anode) as well as on individual electrodes. The Nyquist plots of the EIS data were fitted with an equivalent electrical circuit to estimate the contributions of various intrinsic resistances to the overall internal MFC impedance. During initial development of the anode biofilm, the anode polarization resistance was found to decrease by over 70% at open circuit and by over 45% at 27 mA/cm 2 , and a simultaneous increase in power density by about 120% was observed. The exchange current density for the bio-electrochemical reaction on the anode was estimated to be in the range of 40-60 nA/cm 2 for an immature biofilm after 5 days of closed circuit operation, which increased to around 182 nA/cm 2 after more than 3 weeks of operation and stable performance in an identical parallel system. The polarization resistance of the anode was 30-40 times higher than that of the ferricyanide cathode for the conditions tested, even with an established biofilm. For a two-chamber MFC system with a Nafion 1 117 membrane and an inter-electrode spacing of 15 cm, the membrane and electrolyte solution dominate the ohmic resistance and contribute to over 95% of the MFC internal impedance. Detailed EIS analyses provide new insights into the dominant kinetic resistance of the anode bio-electrochemical reaction and its influence on the overall power output of the MFC system, even in the high internal resistance system used in this study. These results suggest that new strategies to address this kinetic constraint of the anode bio-electrochemical reactions are needed to complement the reduction of ohmic resistance in modern designs.

Assessment of the Effects of Flow Rate and Ionic Strength on the Performance of an Air-Cathode Microbial Fuel Cell Using Electrochemical Impedance Spectroscopy

“…The rapid decrease in R An is attributed to the inoculum for the MFC originating from an already mature MFC. Previous results reported by Ramasamy et al [24] indicate that anode resistance is initially high and then decreases over time as the biocatalyst acclimates to the MFC environment for exoelectrogenic behavior. The time for such changes to be observed for Ramasamy et al was approximately three weeks, likely due to the inoculum originating from an anaerobic sludge.…”

Impedance and Thermodynamic Analysis of Bioanode, Abiotic Anode, and Riboflavin-Amended Anode in Microbial Fuel Cells

“…They indicates anode biofilm facilitated electron transfer to the anode surface. [9][10][11][12] Initial development of anode biofilm during the first five days decreased anodic charge transfer resistance by about 40% (from 2.6 to 1.5 kΩ cm 2 at 0.27 A/m 2 ) in a ferricyanide-cathode MFC, with increasing power density by about 120%. 11 Anodic charge transfer resistance decreased by ~75% (from 0.073 to 0.017 kΩ cm 2 at 2.63 A/m 2 ) in an air-cathode MFC, with increasing anodic capacitance during 70-day biofilm enrichment.…”

The potential of whey in driving microbial fuel cells: A dual prospect of energy recovery and remediation

“…The advantage of high COD at start-up would be that the substrate ceases to be the limiting factor in electricity generation. Higher conductivity reduces the resistance of the medium, thus, generally increasing the power output and shortening the onset of the maximum power density (Ramasamy et al, 2008;Mohan and Das, 2009).…”

“…In addition, there is a benefit on the kinetics due to reduced activation loss (Ramasamy et al, 2008). Thus, increased microbial competion could also have limited process or biofilm formation in the mixed culture and consequently, less power was produced.…”