Investigation of the promotion effect of Mo doped CuO catalysts for the low-temperature performance of NH3-SCR reaction

A novel Mo-doped CuO catalyst is developed and used for low-temperature NH₃-SCR reaction. Compared with the undoped CuO sample, the Mo doped CuO catalyst shows an increased SCR performance with above 80% NO_x conversion at 175 °C. The XRD and Raman results have confirmed the incorporation of Mo metal ions into CuO lattice to form Mo-O-Cu species which may be related to the enhanced SCR activity. The XPS and UV–vis results reveal the creation of electron interaction between Cu and Mo in this Mo-O-Cu system which provides an increased amount of Lewis and Brønsted acid sites, thereby promoting the adsorption capacity of NH₃ and NO_x as verified by NH₃-TPD and NO_x-TPD characterization. Besides, it also promotes the formation of oxygen vacancies, leading to the increasing of chemisorbed oxygen species, which improves the NO oxidation to NO₂ activity. Furthermore, in situ DRIFTS technology was also used to study the reaction mechanism of this Mo doped CuO catalyst. The formed NO₂ could react with NH_x (x = 3, 2) species to enhance the low-temperature NH₃-SCR activity via the “fast-SCR” reaction pathway. The nitrate and nitrite ad-species may react with NH₃ and NH₄⁺ ad-species through the L-H pathway.