Fabrication and characterization of carbon-based nanostructured electrodes for Microbial Fuel Cells (MFCs)

Abstract

Microbial Fuel Cells (MFCs) are bioelectrochemical systems that can produce bioelectricity from organic matter. Wastewater from urban, domestic or industrial origin can be used as a fuel to produce electricity. In addition, the amount of pollutants and contaminants decreases during the production of bioelectricity. Thus, such bioelectrochemical systems produce renewable energy and, simultaneously, can be used as a novel technology for wastewater treatment. However, the efficiencies obtained are still too low and the output voltage of the MFCs need to be increased. Furthermore, the overall cost of the cell must be reduced in order to promote this technology into the market. Here, we have studied the growth of graphene nanowalls (GNWs) on stainless-steel substrate 304 (SS), which can be used as electrodes in air-cathode MFCs. Growth parameters have been optimized to obtain dense carbon nanostructures on both SS foil and mesh. MFCs with different electrodes have been prepared to study the effect of different parameters and to determine whether the presence of carbon nanostructures results in an increase of the electrochemical efficiency. An oxygen plasma treatment has been performed to study its effect on the properties of the electrodes. Finally, MnO2 has been electrochemically deposited to determine its catalytic effect in the oxygen reduction reaction (ORR) that takes place on the cathode. Results show an increase in the output voltage and power density when GNWs electrodes are compared to MnO2 bare electrodes, with a maximum power density of 9 mW/m2. Moreover, the influence of the oxygen plasma post-treatment, performed on the nanostructures, over microbial communities developed as biofilm in the anode is demonstrated. Overall, this study shows the potential of GNWs to increase the yield of MFCs