How the Morphology of NiO-Decorated CeO₂ Nanostructures Affects Catalytic Properties in CO₂ Methanation

Effects of morphology and exposed crystal planes of NiO-decorated CeO₂ (NiCeO₂) nanostructured catalysts on activity during CO₂ methanation were examined, using nanorod (NR), nanocube (NC), and nanooctahedron (NO) structures. The NiCeO₂ nanorods (NiCeO₂-NR) showed superior activity to NiCeO₂-NC and NiCeO₂-NO along with excellent selectivity for CH₄. This material also demonstrated exceptional durability, with no significant loss of catalytic activity or structural change after use. Comprehensive physicochemical characterization as well as density functional theory calculations determined that the high performance of the NiCeO₂-NR was closely related to the large quantity of surface oxygen vacancies and the high degree of reversibility associated with the Ce⁴⁺ ↔ Ce³⁺ redox cycle of the support. These effects originate from the enhanced reactivity of oxygen atoms on the (110) surfaces of the oxide compared with the (100) and (111) surfaces. This information is expected to assist in the rational design of practical catalysts for the activation of CO₂ molecules and other important transformations.