Ni/CeO₂ Nanocatalysts with Optimized CeO₂ Support Morphologies for CH₄ Oxidation

Catalytic oxidation of CH₄ over nonprecious Ni/CeO₂ catalysts has attracted wide attention. Controlling the morphology of a CeO₂ support can enhance the CH₄ oxidation activity without changing the catalyst composition. Herein, a series of 2 wt % Ni/CeO₂ nanocatalysts with different CeO₂ support morphologies (nanoparticles (P), rods (R), cubes (C)) and synthetic procedures (precipitation, sol-gel (SG)) were evaluated for their CH₄ oxidation performance. The redox properties of CeO₂ supports and corresponding Ni loaded catalysts were characterized by H₂-temperature-programmed reduction and oxygen storage capacity (OSC) measurements. The relationship among the CeO₂ morphologies, surface areas, redox properties, and CH₄ oxidation activity for both CeO₂ supports and Ni/CeO₂ catalysts was established. The findings suggest that CeO₂-R has a greater amount of surface oxygen vacancies as well as an improved OSC and CH₄ oxidation activity compared to CeO₂-P and CeO₂-C supports. The same CH₄ oxidation activity pattern was observed for the Ni containing catalysts (Ni/CeO₂-R > Ni/CeO₂-P > Ni/CeO₂-C). Increasing the CeO₂ surface area by using a sol-gel synthesis method (CeO₂-SG) improved the amount of surface oxygen vacancies and CH₄ oxidation performance of CeO₂-SG and Ni/CeO₂-SG compared to CeO₂-R and Ni/CeO₂-R, respectively.