Carbon nanotube modified air-cathodes for electricity production in microbial fuel cells

The use of air-cathodes in microbial fuel cells (MFCs) has been considered sustainable for large scale applications, but the performance of most current designs is limited by the low efficiency of the three-phase oxygen reduction on the cathode surface. In this study we developed carbon nanotube (CNT) modified air-cathodes to create a 3-D electrode network for increasing surface area, supporting more efficient catalytic reaction, and reducing the kinetic resistance. Compared with traditional carbon cloth cathodes, all nanotube modified cathodes showed higher performance in electrochemical response and power generation in MFCs. Reactors using carbon nanotube mat cathodes showed the maximum power density of 329 mW m^-2; more than twice that of the peak power obtained with carbon cloth cathodes (151 mW m^-2). The addition of Pt catalysts significantly increased the current densities of all cathodes, with the maximum power density obtained using the Pt/carbon nanotube mat cathode at 1118 mW m^-2. The stable maximum power density obtained from other nanotube coated cathodes varied from 174 mW m^-2 to 522 mW m^-2. Scanning electron micrographs showed the presence of conductive carbon nanotube networks on the CNT modified cathodes that provide more efficient oxygen reduction.