The role of two catalysts Pt/Al2O3 and Ru/NaY on the oxidation of carbon by NO2 was investigated in the temperature range 300-400 degrees C. In the case of Pt/Al2O3 no significant catalytic effect on the carbon oxidation rate is observed although decomposition of NO2 takes place on the noble metal and leads to the formation of NO. This result suggests that the amount of the oxygen atoms transferred from the metallic surface sites to the carbon surface to form C(O) complex is negligible. In contrast, in presence of Ru/NaY the oxidation rate of carbon by NO2 is markedly increased. Hence, a significant part of the formed O through catalytic decomposition of NO2 on Ru surface sites is transferred to the carbon surface leading to a larger amount of C(O) complexes on the carbon surface. Thus, the ruthenium surface is a generator of active oxygen species that are spilled over on the carbon surface at 350 degrees C. (c) 2006 Elsevier B.V. All rights reserved.