A polyacrylonitrile-based carbon fiber brush (PAN-CFB) was electrochemically modified and efficiently used as cathode for H2O2 electrogeneration in electro-Fenton process. H2O2 generation performance and energy consumption for PAN-CFB cathode before and after modification were evaluated and compared. For electrochemically modified PAN-CFB (EMPAN-CFB) cathode, the maximal H2O2 concentration (approx. 80 mg L-1 by 1000 C charge, >90% current efficiency) appeared at -0.4 and -0.5 V vs. SCE, a ca. 500 mV positive shift compared with the pristine one, showing desirable stability without performance decay after 30 cycles utilization. Moreover, the influence of the distance between anode and cathode as well as the electrolyte concentration on the energy consumption for H2O2 generation was investigated, with obviously reduced energy consumption for the EMPAN-CFB cathode. Finally, methyl orange was decolorized via electro-Fenton process using the EMPAN-CFB cathode and rapid color removal was accomplished in 5 min following the pseudo-first-order kinetic model with high correlation. (C) 2015 Elsevier B.V. All rights reserved.