Date of Completion
This study focused on manganese oxides with a cryptomelane-type octahedral molecular sieve (OMS-2) structure to replace platinum as a cathode catalyst in microbial fuel cells (MFCs). Undoped (ud-OSM-2) and three catalysts doped with cobalt (Co-OMS-2), copper (Cu-OMS-2), and cerium (Ce-OMS-2) to enhance their catalytic performances were investigated. The novel OMS-2 cathodes were examined in granular activated carbon anode based single-chamber MFC (SCMFC) with sodium acetate as the anode reagent and oxygen in air as the cathode reagent. The results showed that after 400 hours of operation, the Co-OMS-2 and Cu-OMS-2 exhibited good catalytic performance in an oxygen reduction reaction (ORR). The voltage of the Co-OMS-2 SCMFC was 217 mV, and the power density was 180±12 mW/m2. The voltage of the Cu-OMS-2 GACMFC was 214 mV and the power density was 165±11 mW/m2. The internal resistance (Rin) of the OMS-2 SCMFCs (18±1 ohm) was similar to that of the platinum SCMFCs (18±1 ohm). Furthermore, the degradation rates of organic substrates in the OMS-2 SCMFCs were twice those in the platinum SCMFCs, which enhance their wastewater treatment efficiencies.
Power generation and organic substrate removal efficiency of Co-OMS-2 and Cu-OMS-2 were also compared with Pt cathodes in continuous-flow SCMFCs under different hydraulic retention times (HRTs) and chemical oxygen demands (CODs). The 600-hr continuous-flow tests showed that Cu-OMS-2 SCMFCs and Co-OMS-2 SCMFCs achieved the stable power generation of 200±8 mV and 190±5 mV, and were 50-60 mV higher than that of Pt SCMFCs. The COD removal efficiencies of Cu-OMS-2 SCMFCs and Co-OMS-2 SCMFCs were 83-87%, which were 15-19% high than that of Pt SCMFCs. 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%. This study indicated that using OMS-2 manganese oxides to replace platinum as a cathodic catalyst enhances power generation, increases contaminant removal, substantially reduces the cost of MFCs, and has a great potential to be applied in real-world wastewater treatment processes.
Li, Xiang, "MANGANESE OXIDE AS A NEW CATHODE CATALYST IN MICROBIAL FUEL CELLS (MFCs)" (2011). Master's Theses. Paper 39.