Inverse CeO ₂ /Cu Catalyst Achieving Enhanced Selective Oxidation of Ammonia

Ammonia (NH3) selective catalytic oxidation (NH3–SCO) is an effective strategy for eliminating excessive ammonia emissions. However, NH3–SCO catalysts generally face an intrinsic conflict between NH3 oxidation activity and N2 selectivity, as increasing NH3 conversion often leads to enhanced formation of undesired byproducts. In this study, we demonstrate that an inverse CeO2/Cu catalyst with enriched CuO–CeO2 interfacial sites can markedly enhance low-temperature NH3 oxidation activity while largely preserving N2 selectivity. Complete NH3 conversion was achieved at around 250 °C with approximately 80% N2 selectivity, and the catalyst exhibited stable performance for over 48 h. Comprehensive characterizations, including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and kinetic studies, indicate that the inverse CeO2/Cu architecture strengthens Cu–O–Ce interactions and interfacial electron transfer, which is consistent with the formation of abundant Cu+–Ov–Ce3+ interfacial sites. These sites synergistically promote the rapid activation of reactant molecules. Moreover, in situ DRIFTS results suggest that the inverse structure alters the dominant reaction intermediates of NH3 oxidation from relatively inert nitrate species to more reactive monodentate nitrates, thereby accelerating the NH3 oxidation process. This study provides new insights and strategies for the rational design of highly active sites in NH3 selective catalytic oxidation.