Construction of CuO/CeO2 Catalysts via the Ceria Shape Effect for Selective Catalytic Oxidation of Ammonia

Abstract

Tuning the interaction between the loaded metal oxide and the support material is an efficient strategy to boost catalytic purification of ammonia (NH3) as an important factor in the formation of haze. Herein, CuO/CeO2 catalysts based on the ceria shape effect (Ce-NR and Ce-NC) are prepared and tested for the selective catalytic oxidation of ammonia (NH3-SCO). The interaction between CuO and CeO2 with different shapes is crucial to regulate the interface structure and the content of oxygen vacancies. The Cu/Ce-NR possesses more Cu+-Ov-Ce3+ interfacial sites and more oxygen vacancies and achieves a higher catalytic activity (T100 = 240 °C) and a lower apparent activation energy (37.18 kJ mol–1) for NH3-SCO compared with Cu/Ce-NC (T100 = 270 °C, 86.57 kJ mol–1). In situ diffuse reflectance infrared Fourier transform spectra and density functional theory calculation results prove that the Cu+-Ov-Ce3+ interfacial site is the main adsorption site for NH3. The further reaction of in situ generated nitrate with NH3 is the rate-determining step over the CuO/CeO2 catalysts, and it is revealed that NH3 much more easily reacts with the monodentate nitrate species formed on the Cu/Ce-NR catalyst than the bidentate nitrate formed on the Cu/Ce-NC catalyst at 240 °C. This study enriches the understanding of designing efficient catalysts by support shape to modulate their interfacial structure and thus improve the activity of NH3-SCO.