Electrochemical impedance study on methyl orange and methyl red as power enhancing electron mediators in glucose fed microbial fuel cell

Methyl orange and methyl red are studied as electron mediators in a glucose-fed microbial fuel cell with graphite anode, Flemion™ membrane and platinum sheet cathode. Anaerobic activated sludge is used as bacterial medium. Maximum output power levels of the cell are about 106 μW/cm2 in the absence of any added mediator, 164 μW/cm2 and 207 μW/cm2 in the presence of 1 mM of methyl orange and 1 mM of methyl red in the anolyte, respectively, normalized to anode geometric surface area. Also addition of these organic mediators increases the open circuit potential and short circuit current of the cell from 425 mV and 1.12 mA/cm2 to 512 mV and 1.51 mA/cm2 for methyl orange and 585 mV and 1.51 mA/cm2 for methyl red. Impedance measurements are performed for the microbial fuel cell in a two electrode configuration. From impedance spectra it is found that the main factor resulting in an increased power level of the cell is the decrease in the anodic charge transfer resistance. It seems this decrease in a direct consequence of more feasible micro-organism assisted anodic oxidation and electron transfer reaction in the anodic compartment in the presence of studied mediators.

► Methyl red and methyl orange as electron mediators for MFC.
► Application of electrochemical impedance to study the effect of mediators.
► Enhanced power output of the MFC.