Tubular nitrogen-doped carbon materials derived from green foxtail as a metal-free electrocatalyst in microbial fuel cells for efficient electron generation

Abstract Oxygen reduction reaction (ORR) on a cathode is a key factor that limits the power generation and application of air-cathode microbial fuel cells. Tubular nitrogen-doped carbon materials synthesized by thermally annealing green foxtail with melamine were investigated as a metal-free electrocatalyst for efficient cathode ORR. Owing to the high specific surface area, tubular and porous structure, and abundant active centers of the pyridinic and graphite nitrogen incorporated carbon matrix, the nitrogen-doped carbon materials showed excellent activity toward ORR in a neutral electrolyte. Oxygen was reduced to water in a four electron reaction on the three-phase boundary of the as-prepared materials. The microbial fuel cell with the nitrogen-doped carbon electrocatalyst prepared at 800 °C had a satisfactory power density and better stability than commercial Pt/C due to its metal-free property and porous structure. Thus, nitrogen-doped carbon materials derived from economical and sustainable biomass could be a potential alternative for the metal-free ORR catalyst in microbial fuel cells with low cost and high electricity generation efficiency.