High-Power Microbial Fuel Cells Based on a Carbon-Carbon Composite Air Cathode

Microbial fuel cells (MFCs) can convert organics in wastewater directly to electricity, and improving oxygen reduction reaction (ORR) performance is critical to their development and future applications. Electrocatalytic ORR performance is determined by the intrinsic activity and accessible amounts of active sites. A surface nitrogen-enriched carbon coaxial nanocable (NCCN) is applied as an ORR electrocatalyst and combined with activated carbon (AC) with 80 wt% addition as a carbon-carbon composite air cathode in MFCs. The fully exposed nitrogen active sites of NCCN contribute to the enhanced ORR activity, while the graphitized core affords a rapid pathway for electron transportation. AC serves as a spacer to construct a porous framework with interconnected ion diffusion channels. This cathode thus exhibits a maximum power density of 2090 mW m^-2 , 120% higher than commercial Pt/C electrocatalysts, and also 6% higher than the pure NCCN, indicating a synergistic effect between NCCN and AC. A high-performance NCCN-AC air cathode with a great promise for future MFC applications is reported and an effective strategy to bridge the electrocatalytic performance from nanomaterials to practical devices is presented.