Ni/CeO₂ Nanocatalysts with Optimized CeO₂ Support Morphologies\nfor CH₄ Oxidation

Abstract

Catalytic oxidation of CH₄ over nonprecious\nNi/CeO₂ catalysts has attracted wide attention. Controlling\nthe morphology\nof a CeO₂ support can enhance the CH₄ oxidation\nactivity without changing the catalyst composition. Herein, a series\nof 2 wt % Ni/CeO₂ nanocatalysts with different CeO₂ support morphologies (nanoparticles (P), rods (R), cubes\n(C)) and synthetic procedures (precipitation, sol-gel (SG)) were evaluated\nfor their CH₄ oxidation performance. The redox properties\nof CeO₂ supports and corresponding Ni loaded catalysts\nwere characterized by H₂-temperature-programmed reduction\nand oxygen storage capacity (OSC) measurements. The relationship among\nthe CeO₂ morphologies, surface areas, redox properties,\nand CH₄ oxidation activity for both CeO₂ supports\nand Ni/CeO₂ catalysts was established. The findings suggest\nthat CeO₂-R has a greater amount of surface oxygen vacancies\nas well as an improved OSC and CH₄ oxidation activity compared\nto CeO₂-P and CeO₂-C supports. The same CH₄ oxidation activity pattern was observed for the Ni containing\ncatalysts (Ni/CeO₂-R > Ni/CeO₂-P > Ni/CeO₂-C). Increasing the CeO₂ surface area by using\na sol-gel synthesis method (CeO₂-SG) improved the amount\nof surface oxygen vacancies and CH₄ oxidation performance\nof CeO₂-SG and Ni/CeO₂-SG compared to CeO₂-R and Ni/CeO₂-R, respectively. Finally, all studied\nNi/CeO₂ nanocatalysts showed improved hydrothermal stability\ncompared to conventional Pd/Al₂O₃.