The performance of phosphorus (P)-doped activated carbon as a catalyst in air-cathode microbial fuel cells

•AC modified by H3PO4 at 80°C and 400°C respectively was used in air-cathode.•The maximum power density was increased by 55% when AC was treated at 400°C.•The ohmic resistance and charge transfer resistance of air cathode were decreased.•P-doped functional group on AC was beneficial for the decrease of resistance. To observe the influence of P-doped activated carbon (AC) in air-cathode microbial fuel cells (MFCs), AC was treated with H3PO4 (1M) at 80°C and 400°C respectively, and then was used as catalyst layer in the air-cathode. The maximum power densities were: 1096±33mW/m2 (SP2, AC treated at 400°C), 954±36mW/m2 (SP1, AC treated at 80°C), which were 55%, 35% higher than the control (708±27mW/m2, untreated AC), respectively. The results of electrochemical impedance spectroscopy (EIS) and the Brunauer–Emmett–Teller (BET) showed that the total resistance was decreased and the pore structure was changed. The analysis of X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) demonstrated that P-doped functional group was produced in SP2, which caused the 15% greater power density than SP1 by increasing O2 adsorption. What is more important, the chemically modified method is simple and economical.