This work aims to study the evolution of NiO/NiAl2O4 redox performance with CO as fuel for Chemical Looping Combustion (CLC) applications. The oxygen carrier (OC) was investigated under alternating oxidizing and reducing conditions in a fixed bed reactor simulating the cyclic conditions of CLC. The study of the operating temperature influence reveals that total reduction capacity increases with temperature, due to the reaction of the binder NiAl2O4. Regeneration step performed under low oxygen concentration (5 vol.%) shows that the decrease in total reduction capacity during multiple cycles is minimized and the purity of produced CO2 is higher. Therefore, carrying out the regeneration step at lower oxygen concentrations can increase oxygen carrier lifetime. Characterization studies revealed the formation of a nickel rich layer at the surface (up to 20 mu m thick at 900 degrees C) and a partial sintering of particles regenerated under 20 vol.% of oxygen. However, these phenomena are not observed on the particles regenerated under low oxygen concentration. The formation of this layer can be explained by the fact that nickel oxidation is carried out by migration of Ni2+ cations through the layer of NiO initially oxidized at the surface of the particle, the layer becomes thicker during cycles, because NiO does not return to its initial position. At higher temperature, the diffusion velocity increases and therefore the layer formed is thicker. Specific surface area of the oxygen carrier decreases as cycles number increases from 9.4 m(2)/g for the fresh material to 4.4 and 2.3 m(2)/g after thirty cycles at 750 degrees C and 900 degrees C respectively. The same trend is observed for porous volume. However, the decrease is lower when particles are regenerated under low oxygen concentration (6 m(2)/g). (C) 2015 Elsevier Ltd. All rights reserved.