Performance optimization of microbial fuel cells using carbonaceous monolithic air-cathodes

Bamboo charcoal tube (BCT) has been demonstrated to be the air-cathode for microbial fuel cells (MFCs). To enhance the performance of MFCs with BCT cathodes, we herein focus on optimizing BCT diameters and doping with nitrogen and phosphorus elements to improve the physical and chemical properties of BCT cathodes. Scanning electron microscope (SEM) analyses indicated that the cathode with 35 mm inner diameter had relatively ideal pore size distribution. Polarization curves, electrochemical impedance spectroscopy, and cyclic voltammetry results suggested that the cathode (35 mm inner diameter) delivered the highest power density of 7.5 +/- 0.6 W m(-3) among the cathodes with different diameters (27, 31, 35 and 39 mm). It was mainly because of its high oxygen reduction reaction performance, low cathode resistance, and beneficial effects on anode biofilm. In addition, rotating disk electrode (RDE) tests revealed that nitrogen and phosphorus doping could significantly improve the ORR catalytic activity of cathode by around 25% in the limiting current density. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.