<p>In this work, Ni-Ga oxides in bulk and supported onto alumina were prepared by coprecipitation and impregnation for the evaluation of the oxidative dehydrogenation (ODH) of ethane assisted by CO₂. X-ray diffraction (XRD) results indicate that the enhanced catalytic activity exhibited by the Ni-Ga oxides bulk catalysts could be related to NiO crystallite size (8&#xa0;nm) in addition to the high dispersion of the active phase observed by scanning electron microscopy (SEM). Diffuse reflectance spectroscopy (UV-Vis DRS) displayed a Ni predominance with octahedral symmetry (O_h) for the catalysts. X-ray photoelectron spectroscopy (XPS) revealed changes in the surface chemical environment for the catalysts related to the gallium promoter effect. Ni 2p_3/2 analysis indicated that the Ni²⁺ and Ni³⁺ ions, Ni²⁺-OH species, or Ni²⁺ vacancies on the surface of the unsupported catalysts have an important role in catalytic activity. In addition, Ga 3d results suggest that the catalytic activity of the unsupported catalysts could be connected to the similar concentration of Ga^y and Ga³⁺ species (ca. 50%), whereas the absence of activity for supported catalysts could be attributed to the Ga³⁺ species concentration higher than 90%. Finally, relationships for ethane conversion and selectivity toward ethylene with the Ox_(nuc)/Ox_(ele) ratio were found. The analysis of the peak areas in O 1s spectra revealed that the higher selectivity toward ethylene of the NiGa-8 catalyst (ca. 95%) could be related to a similar peak area of nucleophilic and electrophilic oxygen species in the surface.</p> Graphical Abstract <p></p>