Effects of Fe (3+) and Cr3+ ions on the performance of direct methanol fuel cell were investigated. The results show that the cell performance decreased remarkably when the concentration of Fe3+ or Cr (3+) exceeded I x 10(-4) mol L-1. Fe3+ displayed a strong negative effect on the catalytic oxidation of methanol, while Cr3+ affected the cell performance primarily by exchanging with protons of the membrane/ionomer and resulted in ionic conductivity losses. Complete recovery of the cell performance was not obtained after flushing the cell with deionized water. (c) 2007 Elsevier Ltd. All rights reserved.