Sequential supercritical carbon dioxide (scCO(2)) deposition was used to deposit Pd c on Pt/BP2000 resulting in PdPt/BP2000 with Pt:Pd atomic ratios varying between 2:1 and 1:4. The average particle size decreased and the particle size distribution became narrower with increasing Pt content. The small particles with sizes between 1 and 4 nm were found to be rich in Pt and particles larger than S nm were found to be rich in Pd. The cyclic voltammetry for hydrogen oxidation reaction indicated that the PtPd/BP2000 (2:1) catalyst had the highest ESA. The shapes of the voltammograms for all Pd containing catalysts resembled the shape of the voltammograms of the Pt/BP2000 catalyst after 300 cycles due to the dissolutioning of the Pd from the catalyst surface. The stability of the prepared catalysts was further evaluated by accelerated degradation tests including potential cycling (0.6-1.2 V) and potential holding tests. The ORR activity decreased after potential cycling for all the catalysts. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.