Treatment of electrodes or catalyst-coated membranes with steam or boiling water for as short as 10 min dramatically increased their performance when tested in proton exchange membrane (PEM) fuel cells afterwards. The treatment was found to be effective for numerous electrodes consisting of various types of carbon-supported Pt catalysts with different Pt loadings. It is proposed that the treatment increases the number of active sites or regions in the catalyst layer which leads to an enhanced catalyst utilization.