Using density-functional theory, we investigated the adsorption and dissociation of CO2 on Ru-19 clusters of nm size. According to our results, the CO2 molecule adsorbed on the rhombus-center region of a double icosahedral Ru-19 nanocluster has the largest adsorption energy, similar to 1.48 eV, and the greatest elongation of C-O bond. Dissociating the first C-O bond of a CO2 molecule we got a reaction barrier of 0.78 eV, smaller than that of adsorbed on otherwise octahedral and low-symmetry Ru-19 cluster structures. To understand the electronic properties, we calculated the electron localization functions and local densities of states, and the result was explicable. (C) 2013 Elsevier B.V. All rights reserved.