Because metal nanoparticles have a high surface area to volume ratio, they can be highly reactive, cost-effective catalysts. However, metallic surfaces are usually too reactive to maintain their metallic character in the presence of oxygen and/or water vapor. Metal nanoparticle catalysts must be handled carefully to avoid oxidation and inactivation. Here, we suggest a facile in situ preparation method for metal nanoparticle catalysts. Copper acetylide and copper methyl-acetylide molecules are based on ionic bonding, and are relatively stable in air. They can be used as a precursor of copper nanoparticles. Due to their instability at increased temperatures, subsequent annealing promotes a segregation reaction into elemental copper and carbon. Transmission electron microscopy and powder X-ray diffraction revealed that the average diameters of the Cu nanoparticles thus formed were 13.3 and 4.4 nm for C2Cu2 and CuCC-CH3 precursors, respectively. This suggests that the substitution of acetylide molecules can control the size of the resulting copper nanoparticles. The primary advantage of this preparation method is that the functional acetylide group can reduce copper cations. No additional reducing agent is required, so no further separation process is necessary. This presents in situ preparation process. The catalytic activity of the resulting Cu nanoparticles was confirmed for a hydrogen storage system. (C) 2011 Elsevier B.V. All rights reserved.