A pulse electrodeposition method of preparing thin platinum catalyst layers for polymer electrolyte membrane fuel cell (PEMFC) cathodes has been developed through surface activation of the gas diffusion layer (GDL) by a wetting agent. The performance of the catalyst layer was optimized by wetting agent type, immersion time in the wetting agent, and pulse deposition parameters such as total charge density, peak current density, and duty cycle ratio. The Toff time played a more important role than the Ton time in determining the electrode characteristics such as high concentration of Pt, smaller particle size, and loading. Pt cathodes prepared using a peak current density of 400 mA/cm(2) with a duty cycle of 10.7% and total charge density of 6 C/cm(2) resulted in a thin platinum catalyst layer (1.92 mu m) and uniformly distributed platinum nanoparticles (3- 4 nm) on the GDL surface. Novel cathodes with Pt loading of 0.33 mg/cm(2) prepared in the present study exhibited 746 mA/cm2 at 0.7 V. (c) 2007 The Electrochemical Society.