The long-term stability of inexpensive metal matrix of cathodes is one of the most important factors limiting the scaling-up of air-cathode microbial fuel cells (MFCs). We demonstrate that the wet proofing by polytetrafluoroethylene (PTFE) increases the performance of nickel foam cathode in MFCs. After the water proofing is applying on the nickel foam (Ni-W), a corrosion inhibition efficiency of 97% is obtained by the measurements of potentiodynamic polarization. Using Pt as the catalyst, the maximum power density of MFC using wet proofed cathode (Ni-W-Pt) is 0.69 +/- 0.01 W m(-2), with a value of 35% higher than 0.51 +/- 0.01 W m(-2) of non-wet proofed cathode (Ni-NW-Pt). Oxygen mass transfer coefficient (k) of Ni-W-Pt cathodes is 0.68 +/- 0.06 x 10(-4) cm s(-1), which is 53% lower than 1.46 +/- 0.07 x 10(-4) cm s(-1) of Ni-NW-Pt, resulted in an enhancement on CEs after wet proofing. Wet proofing on nickel foam also decreases the soluble Ni(2+) concentration by two orders of magnitude during 10 cycles, showing that the pretreatment significantly enhances the stability of metal cathode. (C) 2011 Elsevier B.V. All rights reserved.