To observe the influence of P-doped activated carbon (AC) in air-cathode microbial fuel cells (MFCs), AC was treated with H3PO4 (1 M) at 80 degrees C and 400 degrees C respectively, and then was used as catalyst layer in the air-cathode. The maximum power densities were: 1096 +/- 33 mW/m(2) (SP2, AC treated at 400 degrees C), 954 +/- 36 mW/m(2) (SP1, AC treated at 80 degrees C), which were 55%, 35% higher than the control (708 +/- 27 mW/m(2), 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 O-2 adsorption. What is more important, the chemically modified method is simple and economical. (C) 2014 Elsevier Ltd. All rights reserved.