A theoretical study on the adsorption of the molecular oxygen on the ground state structures of pure Pd-n, Ni-doped Pdn-1 and Pdn/2Nin/2 (n = 4, 6, 8 and 10) clusters was performed. The dissociation pathways of the molecular oxygen on the Pd-4, Pd3Ni and Pd2Ni2 clusters were calculated. All calculations were performed using the auxiliary density functional theory (ADFT) approach as it is implemented in the deMon2k code. The objective of this work was to evaluate how the adsorption energy of the molecular oxygen is modified when the pure Pd clusters are doped with a Ni atom (Ni-doped Pdn-1) and when the composition of the Pd:Ni is 1:1 (Pdn/2Nin/2). Besides, the activation energy for the dissociation of the O-2 on the Pd-4, Pd3Ni and Pd2Ni2 clusters was calculated, too. Higher adsorption energies are found when the molecular oxygen is bound to two Ni atoms. Finally, the Ni-doped Pd-3 and Pd2Ni2 clusters present lower activation energy compared to the one calculated for the pure Pd-4 cluster. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.