The reaction of NO oxidation on Au(1 1 1), either with atomic or molecular oxygen, was studied by means of density functional theory. The oxidation of NO by atomic oxygen is exothermic, it occurs without activation energy barrier but is limited by the energy required to desorb NO2 from the surface (0.78 eV). For NO oxidation with molecular oxygen, two different exothermic reaction routes were analyzed. In one case, the release of gaseous NO2 is limited by pre-adsorption of molecular oxygen on the surface while, in the other, the reaction is facile but the barrier for NO2 desorption needs to be surpassed. (C) 2010 Elsevier B. V. All rights reserved.