High-performance, low-cost, and robust oxygen reduction reaction (ORR) catalysts have played a very crucial role in the development of microbial fuel cells (MFCs). Herein, A novel in-situ Co3O4 nanoparticles (NPs) modified nitrogen-doped graphene with three-dimensional porous structure (3D GN-Co3O4) has been successfully synthesized and employed as an efficient ORR catalyst in MFCs. Benefiting from 3D porous architecture feature, highly intrinsic conductivity and synergistic effect between nitrogen-doped graphene and Co3O4 NPs, the 3D GN-Co3O4 as a cathode catalyst in alkaline condition realizes significantly enhanced electrochemical performance and outstanding cycling stability. Furthermore, the self-assembly of MFCs based on the 3D GN-Co3O4 cathode offers a high power density of 578 +/- 10 mW m(-2), which is even comparable to the commercial Pt/C. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.