Reaction kinetics for microbial-reduced mediator in an ethanol-fed microbial fuel cell

Abstract

Microbial fuel cell (MFC) is an emerging energy production technology which converts the chemical energy stored in biologically degradable compounds to electricity at high efficiency. MFC with added mediator can enhance the electron transfer from the microbes to the anode, and used to treat industrial waste gases. In this work, the rate of microbial-reduced mediator reaction at the surface of glassy carbon (GC) electrode in an ethanol-fed MFC was investigated using cyclic voltammetry (CV), and compared with linear sweep voltammetry (LSV). The CV method provided a better estimation of the kinetic parameters than the LSV method due to low concentrations of the mediators used (0.2-1.0 mM), affecting the Tafel behaviours. All of the voltammograms indicated a quasi-reversible process for the anode reaction. The highest exchange current density (io) of 0.14±0.01 mA/cm2 and the highest power output of 0.008 mW/cm2 were obtained using 0.2 mM N′,N′,N′,N′-TMPD as the mediator. The MFC power density of 0.03 mW/cm2 was achieved for 1 mM N-TMPD. Further increase in the power density (0.16 mW/cm2) was possible with carbon cloth electrode. The results of this study confirmed the advantage of a mediator for gaseous pollutant treatment and electricity production in a MFC.