The preparation and characterisation of Pt nanoparticles electrodeposited on carbon substrates by pulsating electrolysis are presented. The characterisation studies of metal electrodeposits by using SEM, TEM, XRD and cyclic voltammetry revealed the presence of facetted Pt nanoparticles having a predominant (111) preferential crystal orientation. The amount of electrodeposited Pt was determined by means of a spectrophotometric technique. An improvement in performance of the hydrogen/oxygen PEM fuel cell with (111)-type Pt nanoparticles incorporated in the cathode was observed, which was assigned to the decrease of the blocking effect of the cathode electrode surface by intermediate peroxide species produced during the overall oxygen electroreduction process. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.