A series of CeO₂ supports were treated in an N₂ plasma before being impregnated with Ni precursors to evaluate the impact this has on the metal-support interface and catalytic performance. This impact was determined using a suite of characterization methods including X-ray diffraction (XRD), H₂ temperature-programmed reduction (H₂-TPR), ex situ and in situ X-ray absorption spectroscopy (XAS) and in situ Kerr-gated Raman. The combined and self-consistent results indicated that plasma treatment of CeO₂ can lead to the generation of an increasing number of oxygen vacancies, and a loss of long-range order in samples treated for 1 h, realizing a highly defective CeO_x film at the interface between the Ni metal nanoparticles and bulk CeO₂. However, this highly defective CeO_x surface significantly enhances the Ni-CeO_x interaction, resulting in a number of smaller Ni NPs in intimate contact with the support, leading to improved catalytic performance for CO₂ methanation. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that the more defect-dense Ni−CeO_x interface leads to the formation of more bidentate bridged carbonates (vs. bidentate chelate) and which are more readily consumed during reaction, suggesting the identification of an important parameter to effect low-temperature (< 300 °C) CH₄ production.