[Sustainable electricity generation in microbial fuel cells using Fe(III)-EDTA as cathodic electron shuttle]

The rate of oxygen reduction reaction (ORR) at the cathode is a major factor affecting the performance of the microbial fuel cells (MFC). Results showed that when using Fe(III)-EDTA solution as catholyte, the ORR rate was significantly increased and the internal resistance was reduced, consequently leading to an increase in power output. With a concentration of Fe(III )-EDTA at 20.0 mmol/L in the catholyte, the MFC produced the voltage and power density at approximate 200.1 mV and 16.0 mW/m2, respectively, which was increased by 73.2% and 70.1% contrary to the MFC without the presence of Fe(III)-EDTA. The further experiment suggested that Fe(III)-EDTA functioned as electron shuttle to accelerate electron transfer. Fe(III)-EDTA received electron and got reduced to Fe(III)-EDTA, which further provided electrons to oxygen and got reoxidized at the same time. Therefore Fe(III)-EDTA can act as recyclable electron shuttles between cathode electrode and oxygen. The optimum condition in the case of using Fe(III)-EDTA as cathode electron shuttles was tested to be Fe(III)-EDTA concentration at 20.0 mmol/L and pH at 5.0, which allowed MFC produced the maximum power density of 100.9 mW/m2.