Oxidized diamond played a significant role as an efficient support for a Cr2O3-loaded catalyst during the dehydrogenation Of C2H6 to C2H4 in the presence of carbon dioxide at 923 K, giving a 22.5% C2H4 yield with a 87.7% C2H4 selectivity. The activity of the oxidized diamond-supported Cr2O3 catalyst in the presence of CO2 was about 3 times higher than that in the absence Of CO2. The activity of the oxidized diamond-supported Cr2O3 catalyst increased with increasing CO2 Partial pressures. XPS analyses of the fresh and the reacted catalysts in the presence and absence Of CO2 revealed that CO2 maintained the surface Cr2O3 at a higher-oxidation state than the reaction in the absence Of CO2. On the other hand, bulk of Cr2O3 was not reduced in either atmosphere.