Electrode engineering is currently of great significance for addressing the challenge of relatively poor power density faced by microbial fuel cell. This work reported that readily available onion-derived activated carbon (AOC) featured with rich content of nitrogen and phosphorous, opened mesoporous structure, revealed as excellent trifunctional electrode modifier for MFC by boosting the anodic charge transfer efficiency and catalyzing cathodic oxygen reduction, which gave rise to nearly 60% increment in the maximum power density (up to 742 +/- 17 mW m(-2)), and thirdly rendering the device with distinct transient charge storage capacity that is 15 times of the plain counterpart. It's further revealed that these remarkably enhanced performances could be attributable to the improved electrochemical properties, and intrinsic capacitance of anode by AOC, in addition to its comparable electrocatalytic activity but obviously superior stability over Pt/C toward cathodic ORR. It is anticipated that this sustainable electrode modifier facilely obtained from natural plants with triple functionalities, metal-free nature yet low cost hold great potential for real use of MFC. (C) 2018 Elsevier Ltd. All rights reserved.