In Situ Construction of Cu⁺-O_v-Ce³⁺ Sites on CeO₂ for Efficient NH₃ Oxidation

Ammonia (NH₃) emissions adversely affect both the environment and human health. The selective catalytic oxidation of NH₃ (NH₃-SCO) holds great promise for NH₃ abatement; however, there remains a lack of cost-effective NH₃-SCO catalysts with high activity and N₂ selectivity for practical applications. This study reports on a strategy for constructing an outstanding NH₃ oxidation catalyst via the in situ doping of Cu into CeO₂ nanorods. The designed CeCuO_x nanorod catalyst shows remarkable activity, N₂ selectivity, and stability for NH₃ oxidation, achieving complete conversion below 250 °C, with ≈80% N₂ selectivity. The results of various characterization tests and density functional theory (DFT) calculations show that the addition of Cu induces the formation of abundant Cu⁺-O_v-Ce³⁺ active sites on the CeO₂, which are beneficial for the adsorption and activation of reactants. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirms that the addition of Cu switches the primary intermediate species of NH₃ oxidation from bidentate nitrate species to monodentate nitrate species, which accelerates the rate-determining step of NH₃-to-N₂ oxidation. Therefore, doping Cu into CeO₂ greatly improves its NH₃ oxidation activity and N₂ selectivity. This study provides valuable insights into the construction of highly active sites for NH₃ oxidation.