Pt nanoparticles is successfully deposited onto polyethyleneimine-functionalized carbon black by a non-covalent method, where the functionalization is carried out using 0.1 wt. %, 0.4 wt. %, 0.6 wt. % and 0.8 wt. % polyethyleneimine (PEI) solution and denoted as Pt-xPEI-CB (x = 0.0, 0.1, 0.4, 0.6 and 0.8). The functionalization of carbon black (CB) by PEI affects the Pt nanoparticle size, dispersion and Pt content deposited on CB, preventing Pt nanoparticles from agglomeration. Transmission electron micrograph (TEM) images clearly show a significant agglomeration of Pt nanoparticles for Pt-CB. X-ray photoelectron microscopy (XPS) analysis shows the highest metallic Pt content for Pt-0.4PEI-CB and the membrane electrolyte assembly (MEA) fabricated with that also shows the highest power generation: that is, 1.05 W/cm(2) at 2.31 A/cm(2). Electrochemical active surface areas (ECSAs) for Pt-xPEI-CB are estimated to be 58.4 m(2)/g, 49.7 m(2)/g, 54.4 m(2)/g, 52.7 m(2)/g and 42.5 m(2)/g for x = 0.0, 0.1, 0.4, 0.6 and 0.8, respectively. Cationic PEI also plays an important role for the durability of electrochemical catalyst: that is, the electrochemical active surface area (ECSA) after 1200 cycle operation for Pt-CB is more significantly decreased by 72% than those of Pt-xPEI-CBs. (C) 2014 Elsevier Ltd. All rights reserved.