The 30 mol% MO (M=Mg, Ca, Sr, Ba)-, 30 mol% BaCO 3 -, and 30 mol% BaX 2 (X=F, Cl, and Br)-promoted Y 2 O 3 catalysts have been investigated for the oxidative dehydrogenation of ethane reaction. Adding BaO or BaX 2 to Y 2 O 3 could significantly enhance the C 2 H 4 selectivity. We also found that the doping of BaX 2 into Y 2 O 3 could considerably reduce C 2 H 4 deep oxidation. Among these catalysts, 30 mol% BaCl 2 /Y 2 O 3 performed the best. It was stable within a reaction period of 40 h, giving a C 2 H 6 conversion, a C 2 H 4 selectivity, and a corresponding C 2 H 4 yield of ca. 72, 74, and 53%, respectively, at 640°C and 6000 mL h −1 g −1 space velocity. X-ray photoelectron spectroscopy and chemical analysis of halides indicated that the Cl − ions were uniformly distributed in 30 mol% BaCl 2 /Y 2 O 3 whereas the halide ions in 30 mol% BaF 2 /Y 2 O 3 and 30 mol% BaBr 2 /Y 2 O 3 were not. With the increase of space velocity, the C 2 H 6 conversion decreased and the C 2 H 4 selectivity increased at 640°C over the 30 mol% BaCl 2 /Y 2 O 3 catalyst. We observed that Cl leaching was not significant in 30 mol% BaCl 2 /Y 2 O 3 . However, gradual Br leaching was observed over 30 mol% BaBr 2 /Y 2 O 3 . X-ray powder diffraction and CO 2 temperature-programmed desorption (CO 2 -TPD) results demonstrated that the 30 mol% BaCl 2 /Y 2 O 3 catalyst is durable and is resistant to CO 2 poisoning whereas the 30 mol% BaO/Y 2 O 3 and BaX 2 (X=F and Br)/Y 2 O 3 catalysts are readily poisoned by CO 2 due to BaCO 3 formation. O 2 -TPD studies showed that the addition of BaO (or BaX 2 ) to Y 2 O 3 could obviously enhance the adsorption of oxygen molecules. We consider that such enhancement is closely associated with the defects generated due to ionic exchanges between the BaO (or BaX 2 ) and the Y 2 O 3 phases. Among the three 30 mol% BaX 2 /Y 2 O 3 catalysts calcined at 900°C, 30 mol% BaCl 2 /Y 2 O 3 showed a cubic Y 2 O 3 lattice most significantly enlarged and a BaX 2 lattice most pronouncedly contracted. In situ laser raman results indicated that there were dioxygen adspecies such as O 2 2− , O 2 n− (1<n<2), O − 2 , and O 2 δ− (0<δ<1) on the 30 mol% BaO/Y 2 O 3 and 30 mol% BaX 2 /Y 2 O 3 catalysts. Electron paramagnetic resonance results indicated that there were monoxygen O − and dioxygen O 2 − species on Y 2 O 3 , 30 mol% BaO/Y 2 O 3 , and 30 mol% BaX 2 /Y 2 O 3 . We suggest that the O 2 − O 2 n− , O 2 δ− , and O 2 2− species participate in the selective oxidation of ethane to ethene whereas the O − species were responsible for the deep oxidation of ethane.