Fe3O4 was added into the anode to improve the performance of microbial fuel cells (MFCs). Stainless steel mesh (SSM), activated carbon (AC) with SSM (AcM) and Fe3O4 added AcM (AcFeM) anodes had been made and investigated by electrochemical measurements. The maximum power density of AcFeM anode (809 +/- 5 mW/m(2)) is 22% higher than that of AcM (664 +/- 17 mW/m(2)), and 56 times higher than that of SSM anode (14 +/- 0.3 mW/m(2)). Tafel tests indicate that the anode modified by Fe3O4 is kinetically more advantageous. It is demonstrated for the first time that the capacitance of anode increased after the addition of Fe3O4. With 10 min of interruption, AcFeM exhibites a 41% higher cumulative charge of 3566 +/- 32 C/m(2) and a 32% higher net capacitance charge of 389 +/- 18 C/m(2) than those of the AcM control (2529 +/- 22 and 294 +/- 30 C/m(2)), indicating that the improvement of anode performance can be also attributed to the enhancement of capacitance. (C) 2012 Elsevier Ltd. All rights reserved.