Electricity generation in continuous flow microbial fuel cells (MFCs) with manganese dioxide (MnO2) cathodes

A novel cost-effective cathode catalyst, manganese dioxide (MnO2) featured with a cryptomelane-type octahedral molecular sieve (OMS-2) structure, was examined in continuous flow microbial fuel cells (MFCs). Power generation and organic substrate removal efficiency of two metal ions doped OMS-2 cathodes (cobalt (Co)-OMS-2 and copper (Cu)-OMS-2) were compared with platinum (Pt) cathodes under different hydraulic retention times (HRTs) and chemical oxygen demands (CODs). The 600-h continuous flow tests showed that Cu-OMS-2 MFCs and Co-OMS-2 MFCs achieved the stable power generation of 200 ± 8 mV and 190 ± 5 mV, and were 50–60 mV higher than that of Pt MFCs. The COD removal efficiencies of Cu-OMS-2 MFCs and Co-OMS-2 MFCs were 83–87%, which were 15–19% higher than that of Pt MFCs. The power generation and COD removal efficiency increased with longer HRTs. The Cu-OMS-2 exhibited the highest power density (201 mW/m2) at the COD of 1000 mg/L. However, Co-OMS-2 cathodes had the better performance than Cu-OMs-2 at high COD concentrations of 2000–4000 mg/L, with the power density of 897 mW/m2 and COD removal efficiency of 46%. The continuous flow MFC tests demonstrated that the fast reaction rate of OMS-2 cathodes enhanced power generation and COD removal efficiency, and had a great potential to be applied in real-world wastewater treatment processes.

► Manganese dioxide featured with cryptomelane-type octohedral molecular sieve (OMS-2) structure was used as microbial fuel cells (MFCs) cathode catalysts.
► The novel cost-effective OMS-2 catalysts were examined in continuous flow MFCs.