Electrochemical dealloying of Pt-based bimetallic (alloy) nanoparticles is a promising technique to synthesize active oxygen reduction reaction (ORR) electrocatalysts. Here we present the synthesis of carbon nanotube (CNT) supported Pt-Cu alloy nanoparticles by a two-step synthesis consisting of a polyol reduction using microwave irradiation or conventional heating and a reduction by NaBH4. Coreshell catalysts were obtained by electrochemical dissolution of the Cu atoms from the outer layers of Pt-Cu alloys. The PtCu/CNT catalysts were structurally characterized by XRD, TEM, and ICP-OES while the electrochemical tests were performed by cyclic voltammetry and rotating disk electrode in 0.1 M HClO4. The values of the electrochemically active surface area as well as the mass and surface specific activities depend on the preparation process with the most active catalysts demonstrating up to 4.5 fold activity enhancement compared to commercial Pt/C. Further investigations concerning the age of the catalyst ink used for electrode preparation indicate that this factor should not be neglected during ORR studies on alloy nanoparticles. (C) 2015 Elsevier Ltd. All rights reserved.