Proton exchange membrane fuel cells (PEMFCs) are used in portable devices to generate electrical energy: however, the efficiency of the PEMFC is currently only 40%. This study demonstrates that the efficiency of a PEMFC can be increased to 61% when 1-butyl-3-methylimidazolium tetrafluoroborate (BMI center dot BF4) ionic liquid (IL) is used together with the membrane electrode assembly (MEA). The results for ionic liquids (IL) 1-butyl-3-methylimidazolium chloride (BMI center dot Cl) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMI center dot BF4) in aqueous solutions are better than those obtained with pure water. The current and the power densities with IL are at least 50 times higher than those obtained for the PEMFC wetted with pure water. This increase in PEMFC performance can greatly facilitate the use of renewable energy sources. (C) 2010 Published by Elsevier B.V.