Enhanced performance of a mixed culture microbial fuel cell (MFC) with iron oxide nanostructure cathode

Microbial fuel cell (MFC) is an electrochemical biofuel system that convert chemical energy into electrical energy using microorganisms. MFC efficiency may be greatly increased if an inexpensive, readily available, and effective cathode catalyst is developed for the cathode oxygen reduction reaction (ORR) process. This study explores employing iron oxide nanostructure cathode for ORR in an MFC. In a two-chamber MFC, mixed culture bacteria biofilm on a graphite anode was used. An iron plate was utilized to create an iron oxide nanostructure as a cathode in the MFC. In order to prepare nanostructure oxide, the iron plate was heated in a flame for a predetermined amount of time. The bulk as well as oxidized iron plates were employed separately as ORR cathodes in the MFC. Scanning electron microscopy (SEM) imaging showed that prepared oxide film on iron plate is of nanostructured type showing nano-granular structure. Polarization tests showed that the oxidized iron had a higher catalytic activity towards the ORR than the bulk iron. The highest power density of 16.7 µW was achieved using an iron oxide cathode which is 2.7 times higher compared with bulk iron (6.05 µW). Therefore, iron oxide nanostructures provide considerable output power enhancement probably due to more catalytic properties resulting from increase in specific electroactive surface area and nanoscale effects, thus enhancing the overall ORR reaction rate. Thus, a nanostructured iron oxide cathode may be used to enhance the performance of a microbial fuel cell (MFC) via an easy and affordable procedure.