Enhanced soot oxidation activity over CuO/CeO2 mesoporous nanosheets

Abstract

Developing highly active catalysts for soot elimination has become a research hotspot in environmental catalysis. Herein, CuO/CeO₂ mesoporous nanosheets have been synthesized by combining hydrothermal and wet-impregnation methods, aiming to catalyze NO_x-assisted soot oxidation. Results indicate that CeO₂ mesoporous nanosheets decorated with 7.2 wt% CuO loading showed the best soot oxidation activity, giving a T_m of 494 °C and a nearly 100% CO₂ selectivity under reaction conditions of NO concentration = 500 ppm, 5.0% O₂/N₂ and GHSV = ca. 11 400 h⁻¹. This superior activity can be associated with the synergistic effect of the following factors: firstly, the sheet-shaped morphology together with high surface area enlarged the contact interface between soot and the catalyst; secondly, the mesoporous channels within nanosheets not only favored the enhanced adsorption and diffusion of gas reactants (NO and O₂), but also enlarged the contact interface between the catalyst and gas reactants (NO and O₂); thirdly, the improved redox properties and abundant defective sites facilitated the enhanced adsorption and activation of oxygen species and also favored the enhanced NO oxidation ability to generate NO₂ to take part in soot oxidation, thereby improving soot oxidation activity. Meanwhile, this catalyst also exhibited good stability against structural collapse owing to its highly stable crystal phase and robust morphological structure, demonstrating its potential applications under practical working conditions.