A surface engineering approach was adopted for the preparation of a core-shell structure of bimetallic PtCo nanoparticles to improve catalytic activity for methanol oxidation on a mass basis. Synthesis of core-shell Co@Pt nanocomposite catalysts with different Pt content was carried out by reducing platinum precursors using ethylene glycolcitrate (EG) in aqueous solution containing previously formed Co/C. Characterizations were carried out using transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and electrochemical techniques. The synthesized core-shell Co@Pt nanocomposite catalysts showed enhanced catalytic activity in the methanol oxidation reaction. The enhancement may result from favorable strain effects related to the thickness of Pt shell formed on the non-noble metal substrate. Moreover, the electrocatalytic activity was optimized by tuning shell thickness. This result confirms that changing the Pt shell thickness has a significant effect on the catalytic activities of nonnoble core-noble shell bimetallic nanoclusters. The developed surface-modification method (i.e. by fine-tuning the thickness of Pt shell on the non-noble metal substrate) has great potential application for producing highly active electrochemical catalysts for methanol oxidation on a large scale. The work thus paves the way for further investigating the strain effect in core-shell bimetallic catalysts. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.015203jes] All rights reserved.