We report on the properties and performance of nanoporous proton-conducting membrane-based direct methanol fuel cell DMFC operated with triflic acid. Replacement of sulfuric acid (which adsorbs on platinum) by triflic acid (which does not) and the use of a higher quality membrane led to an increase in cell power by up to 250% (up to 0.5 W/cm(2) at 130 degrees C) and to a decrease in both anodic and cathodic overvoltages. Three more factors seem to be responsible for this high power, reduction in water hydraulic pressure at the cathode, decrease in the partial vapor pressure of water at the cathode, and decrease in cell resistance. (C) 2004 The Electrochemical Society.