| Summary: | Recovering energy from wastewater is an important frontier of environmental engineering and science. Of the many proposed strategies, microbial fuel cells (MFCs) provide a direct path to electricity generation. Here, we report MFCs equipped with floating carbon-cloth air cathodes modified with manganese oxide (MnOx) or Platinum nanoparticle oxygen reduction catalysts. The performances of these MFCs were compared using domestic wastewater in a configuration suitable for electricity generation from primary settling tanks. The open-circuit voltages of the Mn-MFCs decreased gradually over time while those of the Pt-MFCs remained stable indicating that Mn leaching from the electrodes was occurring. Over 90% of the MnOx catalyst was solubilized from the cathode surface within the first two weeks of operation. Initially, the Pt-MFCs did not generate as high of a current density as MnOx but after 55 days, Pt-MFCs had a higher average maximum power density during polarization than Mn-MFCs: 65.4 ± 4.6 and 48.4 ± 10.16 mW/m2 (based on anode geometric surface area), respectively. These results show the importance of evaluating promising alternative MFC cathode catalyst like MnOx in actual wastewater since it is difficult to predict how new catalysts designed to decrease cost yet increase the efficiency of the reduction of oxygen will respond in real-world wastewater applications. Keywords: Microbial fuel cell, Biofilm, Wastewater, Energy recovery, Catalyst
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