A diffusion barrier is designed to control methanol transport to an anode catalyst layer, and hence, to suppress the methanol crossover. Based on a theoretical calculation, four layers of Nafion 117 membrane were served as the barrier. It is observed that the limiting current density for 10 M MeOH is about 250 mA/cm(2), which is between that of 2 M MeOH and 3 M MeOH in a conventional direct methanol fuel cell without a diffusion barrier. This demonstrates that a Nafion membrane barrier can efficiently control methanol transport. The peak power density achieves 40 mW/cm(2) at 50 degrees C for 10 M MeOH. (c) 2006 The Electrochemical Society.