P3: Improved Carbon Cathodes for Microbial Fuel Cells (MFCs)

MFCs through the catalytic activity of microorganisms, extract energy from the organic matter contained in wastewater to produce electricity, and consist of two half-cells; the anode and the cathode. Unless prohibitively expensive metals and catalysts are used, the cathode is currently the limiting factor in improving the performance and sustainability of MFCs. Both half-cells require high surface area electrodes, to facilitate different reactions; the anode in order to support a healthy biofilm growth, and an air-cathode to support the oxygen reduction reaction. The aim of this study is the comparison between two high surface area and catalyst free cathode electrodes: carbon fibre veil and carbon cloth coated with carbon powder Micro Porous Layer (MPL) in dual-chamber MFCs of 25mL volume each. Folded 270cm² carbon veil (CV) is compared to a single 10cm² MPL (sMPL) and a folded 150cm² MPL (fMPL), as well as against the MPL as working as a Membrane-Electrode-Assembly (mMPL). Preliminary results show that under an initial fixed load (8200Ohm), fMPL produced 27μW, which is 3-fold higher compared with the control (CV 9μW). Following polarisation experiments and subsequent connection of the resultant maximum-power-transfer resistance values, sMPL generated 67μW, thus outperforming the fMPL (60μW) and CV (27μW).

MPL is outperforming the carbon veil material, used as cathode electrodes in our set up. This may be due to its micro-porous structure, which results in a higher surface area as well as higher carbon loading, which results in higher conductivity, thereby making it an attractive alternative for use in MFCs.