Co core-Pt shell nanoparticles (denoted as Co1-x@Pt-x where x = 0.33, 0.43, 0.60, 0.68, 0.82) and carbon supported Co core-Pt shell nanoparticles (denoted as Co1-x@Pt-x/C where x = 0.60, 0.68, 0.82) (Co1-x@Pt-x/C = 43%), which are synthesized through a polyol reduction process with oleic acid as a surfactant, have been investigated as catalysts for hydrogen generation from hydrolysis of ammonia borane (NH3BH3) at 25 +/- 0.5 degrees C. The as-prepared Co core-Pt shell nanoparticles are uniformly dispersed on carbon surface with diameters of about 3 nm. It is found that the catalysts show favorable performance toward the hydrolysis of NH3BH3 and the catalytic activity is associated with the ratio of Pt to Co. Among the catalysts studied, [email protected]/C ([email protected]/C = 43%) displays the highest catalytic performance, delivering a high hydrogen-release rate of 4874 mL min(-1) g(-1) (per catalyst). (C) 2010 Elsevier B.V. All rights reserved.