Carbon nanotube/nanofiber papers (i.e., buckypapers) supported Pt catalysts were synthesized using a supercritical fluid deposition method for proton exchange membrane fuel cell (PEMFC) applications. The process involves impregnating buckypapers with plantinum precursor PtMe2COD (dimethyl (cyclooctadiene) platinum(II)) in supercritical CO2 fluid and thermally reducing PtMe2COD in N-2 at 200 degrees C. Highly dispersed fine platinum (Pt) particles were obtained on the buckypaper support resulting in a high electrochemical surface area (ECSA) of 100 m(2)/g. With an ultralow Pt loading of 25 mu g/cm(2) in Pt/buckypaper cathode catalyst layer, cell performance reached as high as 400 mW/cm(2) at 0.65 V and 830 mW/cm(2) at peak. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3594097] All rights reserved.