Oxygen reduction reaction (ORR) in microbial fuel cell (MFC) was evaluated by using chemical activated nitrogen-doped carbon nanofibers (ANCNFs) as cathode catalyst. ANCNFs are synthesized through modified oxidative template assembly route and then activated by KOH reagent. The as-prepared ANCNFs formed three-dimensional carbonfiber framework with large specific surface area and hierarchical tetramodal pore size distribution spanning the micro-, meso- and macro pore range, centered at 0.48, 4.0, 18 and 70 nm. Compared with unactivated nitrogen-doped carbon nanofibers (NCNFs), ANCNFs exhibited a more positive onset potential, higher current density as well as higher electron transfer number in neutral environment, highlighting the importance of chemical activation process for improving the ORR performance. MFCs equipped with ANCNFs catalyst exhibited a high power output of 1377 +/- 46 mW m(-2), which is about 1.5 times the output of NCNFs cathode (921 +/- 29 mW m(-2)), and as high as nearly 4 times of plain cathode (341 +/- 9 mW m(-2)). (C) 2014 Elsevier B.V. All rights reserved.