Cost-Effective Surface Modification of Carbon Cloth Electrodes for Microbial Fuel Cells by Candle Soot Coating

This study explored an economically-feasible and environmentally friendly attempt to provide more electrochemically promising carbon cloth anodes for microbial fuel cells (MFCs) by modifying them with candle soot coating. The sponge-like structure of the deposited candle soot apparently increased the surface areas of the carbon cloths for bacterial adhesion. The super-hydrophilicity of the deposited candle soot was more beneficial to bacterial propagation. The maximum power densities of MFCs configured with 20-s (13.6 ± 0.9 mW·m−2), 60-s (19.8 ± 0.2 mW·m−2), and 120-s (17.6 ± 0.8 mW·m−2) candle-soot-modified carbon cloth electrodes were apparently higher than that of an MFC configured with an unmodified electrode (10.2 ± 0.2 mW·m−2). The MFCs configured with the 20- and 120-s candle-soot-modified carbon cloth electrodes exhibited lower power densities than that of the MFC with the 60-s candle-soot-modified carbon cloth electrode. This suggested that the insufficient residence time of candle soot led to an incomplete formation of the hydrophilic surface, whereas protracted candle sooting would lead to a thick deposited soot film with a smaller conductivity. The application of candle soot for anode modification provided a simple, rapid, cost-effective, and environment-friendly approach to enhancing the electron-transfer capabilities of carbon cloth electrodes. However, a postponement in the MFC construction may lead to a deteriorated hydrophilicity of the candle-soot-modified carbon cloth.