The mechanism of alkyne homocoupling over gold nanoparticles and clusters, isolated and supported on CeO2, has been theoretically investigated by means of periodic DFT calculations. The theoretical study indicates that O-2 dissociation on gold generates basic O atoms able to abstract the proton of the allcyne, and cationic Au delta+ and Au+ species that decrease the activation barrier for the C-C bond forming step. Kinetic results show that the base-free homocoupling of alkynes is effectively catalyzed by gold nanopartides supported on different solids, and confirm the theoretical prediction that the dissociation of oxygen on the gold nanoparticle is the controlling step of the global reaction. (C) 2014 Elsevier Inc. All rights reserved.