Novel Cu@Ni catalysts consisting of a Cu core and a Ni shell and Ni@Cu catalysts have been synthesized by successive reduction of Cu and Ni sources dissolved in ethanol. A combination of transmission electron microscopy (TEM), UV-vis spectroscopy, X-ray diffraction (XRD), CO chemisorption, as well as thermogravimetric analysis (TGA) was used to characterize the core-shell nanoparticle catalysts. The powder XRD patterns, CO chemisorption data, and UV-vis spectra indicated the formation of core-shell structures in the bimetallic Cu-Ni nanoparticles. Cu5@Ni5 and [email protected] nanoparticles with an average particle size of 4.7 and 5.4 nm, respectively, were observed in TEM images. Alumina-supported Ni@Cu nanoparticle catalysts were found to possess similar activity in the water-gas-shift (WGS) reaction to supported Cu catalysts, while supported Cu@Ni catalysts showed comparable WGS activity to supported Ni catalysts and reduced extent of undesirable methanation side-reaction. (C) 2012 Elsevier B.V. All rights reserved.