Improved interfacial oxygen reduction by ethylenediamine tetraacetic acid in the cathode of microbial fuel cell

In this study, ethylenediamine tetraacetic acid (EDTA) was investigated as a new kind of non-polymeric catalyst binder to improve interfacial oxygen reduction reaction (ORR) for the cathode of microbial fuel cell (MFC). The electrochemical analysis and MFC tests show negative correlation between ORR activity and molar concentration of EDTA applied during electrode preparation. In particular, the 0.02mol/L-EDTA yields higher ORR activity than other binder materials like Nafion, water, 0.1mol/L-EDTA and 0.2mol/L-EDTA, as indicated by the strongest response of ORR current and the smallest charge-transfer resistance. Accordingly, the MFC with cathode of 0.02mol/L-EDTA produced a maximum power density of 722mW/m², accounting for a value approximately 42% higher than that of commercial Nafion binder (5wt%, 507mW/m²). The improved ORR activity should be attributed to the enhanced proton transfer from phosphate ions to EDTA-involved three-phase boundary as a result of dipole ion bonds on nitrogen atoms having unshared pair of electrons in EDTA molecule.