The partial hydrogenation of 1,3-butadiene (13BD) to several C4H8 products, including 1-butene (1B), 2-butene (2B) and butan-1,3-diyl (B13R), on both Pd/Ni(1 1 1) and Pd-3/Ni(1 1 1) bimetallic surfaces was theoretically investigated using OFT methods. For that purpose, different intermediates C4H7 and C4H8 radical species were evaluated according to the Horiuti-Polanyi mechanism performed in two sequential steps. The whole process was found to be exothermic on Pd/Ni(1 1 1) and endothermic on Pd-3/Ni(1 11). Furthermore, the former surface, where the intermediate adsorptions are more favorable, exhibits lower activation barriers than Pd-3/Ni(1 1 1). On both surfaces, the B13R formation is associated with high transition state energies through the pathways studied here; for this reason, it is extremely improbable to obtain B13R. Our calculations predict that on the Pd/Ni(1 1 1) catalyst model, the products would be mainly the butene isomers, with a little more selectivity toward 2B, in contrast to the pure Pd surface and in agreement with experimental data. (C) 2014 Elsevier B.V. All rights reserved.