Nanoshaped CuO/CeO₂ Materials: Effect of the Exposed Ceria Surfaces on Catalytic Activity in N₂O Decomposition Reaction

This study reports a thorough investigation of nanosized CuO/CeO₂ materials as an efficient catalyst for decomposition of N₂O, which is a strong greenhouse gas largely produced by chemical industry. Effect of terminating CeO₂ crystalline planes ({100}, {110}, and {111}) on the behavior of CuO dispersed over CeO₂ nanocubes, nanorods and polyhedral crystallites was examined in detail by using a variety of catalyst characterization techniques. The 4 wt % Cu was found as the most advantageous metal loading, whereas higher Cu content resulted in lower dispersion and formation of significantly less active, segregated bulk CuO phase. It was discovered that CuO/CeO₂ solids should enable both excessive oxygen mobility on the catalyst surface as well as formation of highly reducible Cu defect sites, in order to ensure high intrinsic activity. Detailed studies further revealed that CeO₂ morphology needs to be tailored to expose {100} and {110} high-energy surface planes, as present in CeO₂ nanorods. Oxygen mobility and regeneration of active Cu phase on these surface planes is easier, which in turn facilitates higher catalytic activity through the recombination of surface oxygen atoms and desorption as molecular oxygen that replenishes active sites for subsequent catalytic cycles. As a consequence, CuO supported on CeO₂ nanorods demonstrated lower activation energy (87 kJ/mol) in N₂O decomposition reaction compared to catalysts based on CeO₂ nanocubes (102 kJ/mol) or polyhedral CeO₂ (92 kJ/mol)