To date different electrode materials have been used to improve the performance and reduce the costs of microbial fuel cells (MFCs). Particularly, there is a need to avoid the use of expensive Pt-based cathode materials. Here, we explored the use of vertically aligned carbon nanotubes (CNTs) deposited by plasma-enhanced chemical vapor deposition as cathode material in single chamber MFCs. In order to improve cell performance and lower the oxygen reduction reaction resistance at the cathode side, MnO2 catalyst was electrochemically deposited on the CNTs. Results show an increase in the output voltage and power density by two orders of magnitude when compared to plain stainless-steel electrodes, with a maximum power density of 24 mW m(-2). Furthermore, the influence of medium solution in the electrolyte was also examined. Results demonstrate that microbial communities developed as biofilm in the anode were limited by substrate metabolic liability. The presence of a labile organic source (acetate) promoted an increase of one order of magnitude in cell performance. Overall, this study shows the potential of aligned CNTs to increase yield of MFCs.