Reaction Sensitivity of Ceria Morphology Effect on Ni/CeO₂ Catalysis in Propane Oxidation Reactions

CeO 2 nanocubes (c-CeO 2 ), nanoparticles (p-CeO 2 ), and nanorods calcined at 500 °C (r-CeO 2 -500) and 700 °C (r-CeO 2 -700) were used as supports to synthesize a series of Ni/CeO 2 catalysts for the propane combustion and oxidative dehydrogenation of propane (ODHP) reactions. The Ni-CeO 2 interaction greatly promotes the reducibility of CeO 2, but CeO 2 morphology-dependent Ni-CeO 2 interaction was observed to form different speciation of Ni species (Ni 2+ dissolved in CeO 2, highly dispersive NiO, NiO aggregate) and oxygen species (strongly activated oxygen species, medially activated oxygen species, weakly activated oxygen species) in various Ni/CeO 2 catalysts. Ni-CeO 2 interaction is stronger in Ni/c-CeO 2 catalysts than in other Ni/CeO 2 catalysts. Different morphology-dependences of Ni/CeO 2 catalysts in propane combustion and ODHP reactions were observed. The Ni/r-CeO 2 -500 catalyst with the largest strongly activated oxygen species is most catalytic active in the propane combustion reaction while the Ni/c-CeO 2 catalyst with the largest amount of weakly activated oxygen species exhibits the best catalytic performance in the ODHP reaction. Thus, the CeO 2 morphology engineering strategy is effective in finely tuning the metal-CeO 2 interaction and the reactivity of oxygen species to meet the requirements of different types of catalytic oxidation reactions.