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A low cost iron phthalocyanine (FePc)-MnOx composite catalyst was prepared for the oxygen reduction reaction (ORR) in the cathode of microbial fuel cells (MFCs). The catalysts were characterised using rotating ring disc electrode technique. The n number of electrons transferred, and H2O2 production from ORR was investigated. The FePc–MnOx composite catalyst showed higher ORR reduction current than FePc and Pt in low overpotential region. MFC with composite catalysts on the cathode was tested and compared to Pt and FePc cathodes. The cell performance was evaluated in buffered primary clarifier influent from wastewater treatment plant. The membrane-less single chamber MFC generated more power with composite FePcMnOx/MON air cathodes (143 mW m−2) than commercial platinum catalyst (140 mW m−2) and unmodified FePc/MON (90 mW m−2), which is consistent with the RRDE study. The improvement was due to two mechanisms which abate H2O2 release from the composite. H2O2 is the reactant in two processes: (i) chemical regeneration of MnOx after electro-reduction to Mn2+, and (ii) peroxide undergoing chemical disproportionation to O2 and H2O on an electrochemically aged manganese surface retained in the film. Process (i) has the potential to sustain electrochemical reduction of MnOx at cathode potentials as high as 1.0 VRHE.
Burkitt et al. (Fri,) studied this question.