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

Abstract

Impedance changes of the anode, cathode and solution were examined for an air-cathode microbial fuel cell (MFC) under varying conditions. An MFC inoculated with a pre-enriched microbial culture resulted in a startup time of less than ten days. Over this period, the anode impedance decreased below the cathode impedance, suggesting a cathode-limited power output. Increasing the anode flow rate did not impact the anode impedance significantly, but it decreased the cathode impedance by 65%. Increasing the anode-medium ionic strength also decreased the cathode impedance. These impedance results provide insight into electron and proton transport mechanisms and can be used to improve MFC performance.

Electrochemical characterization of microbial bioanodes formed on a collector/electrode system in a highly saline electrolyte

“…A similar decrease of the charge transfer resistance correlated with an increase of the current or power density provided by an MFC has already been reported in the literature [11]. The charge transfer resistance of a microfibrous carbon paper bioanode has been observed to decrease from 2.6 kΩ·cm 2 to 480 Ω·cm 2 in 3 weeks in an MFC inoculated with a mixed culture from anaerobic sludge and fed with acetate [24].…”

“…As the research domain progressed, studies have started to focus on the detailed characterization of individual microbial electrodes rather than the investigation of whole electrochemical set-ups [1]. EIS has been used to investigate the growth of biofilms on different microbial electrodes [3,[8][9], together with the effect of various parameters that influence the charge transfer resistance between biofilm and electrode, such as electrode material [6], pH [5,10], medium ionic strength [11] or the presence of microbially secreted mediators [12]. EIS has also shown the capability to monitor the evolution of the microbial community during the formation of an electroactive biofilm [13].…”

A Dual-Channel, Interference-Free, Bacteria-Based Biosensor for Highly Sensitive Water Quality Monitoring

“…Flow rate is another critical parameter that has a substantial influence on microbial metabolisms and microbial biofilm formation, leading to changes in the MFC performance [20,23,24]. Mass transfer and reaction kinetics on the anode can be actively altered by small changes in flow rates [20,23].…”

“…Mass transfer and reaction kinetics on the anode can be actively altered by small changes in flow rates [20,23]. Furthermore, the flow rate is highly related to shear rate, which is one of the parameters to control biofilm formation [24].…”

A comprehensive impedance journey to continuous microbial fuel cells

“…A way to reduce R dif is to decrease the HRT which creates more uniform COD concentrations across the MFC [5] and moderates the effective thickness of the hydrodynamic diffusion layer. The cathode is typically the rate-limiting component of MFCs [12][13][14].…”