1, Indian Institute of Technology Kharagpur, Kharagpur, , India
Oxygen is most prominent terminal electron acceptor for microbial fuel cells (MFCs) and oxygen reduction reaction (ORR) governs the performance of this system. However, high cathode overpotential losses during ORR cause serious performance depletion in MFC in short and long run. Therefore, it is necessary to develop low cost sustainable cathode catalysts to improve ORR in order to enhance power generation from MFCs. The present study demonstrates synthesis of a ferromagnetic low-cost cathode catalyst of family metal co-doped ferrite, CoZnFe2O4, using a simple one-pot high temperature redox process. The results obtained from X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed successful synthesis of CoZnFe2O4. The electrochemical results carried out under air saturated 1 N KCl as neutral solution for evaluating the ORR kinetics supported with this catalyst showed excellent redox current of 34.2 mA for cathode and 5.9 mA for anode with less charge transfer resistance of 0.7 mΩ. Under nitrogen purged 1 N KCl solution, these redox peaks were unnoticeable, conforming that the major reaction was ORR supported by CoZnFe2O4 catalyst. Thus, the MFC using this catalyst in cathode could generate an excellent power density of 9.6 W/m3 which was found about 5 times higher than the power density of 1.96 W/m3 obtained from a MFC using cathode having no catalyst and was noted surprisingly higher than the power density of MFC with Pt-C cathode (8.1 W/m3). The chemical oxygen demand (COD) removal efficiency was about 83 to 88 % from all test MFCs, revealing bifunctional capabilities of MFCs for treatment of sanitary wastewater along with bioenergy recovery. The results obtained from this experiment set the synthesized catalyst in a position to replace mostly used Pt-C catalyst for MFCs.