Optimized local geometry and electronic structure of MoO3/CeO2 catalyst by adding copper cations for boosted nitrogen oxide reduction performance

Hexavalent Metal Cations Doped into Ceria Inducing the Formation of Binuclear Sites Ce3+–O–Ce3+ to Boost the NH3-SCR Reaction

“…Both catalysts exhibited the typical diffraction peaks of cubic fluorite CeO 2 (JCPDS# 65-2975), , indicating the high dispersion of the doped Mo species without the formation of the MoO x phase, and the Ce 0.98 Mo 0.02 O x catalyst maintained the original structural feature of the CeO 2 catalyst. As shown in Figures S3 and a, the Raman spectra indicated that both CeO 2 and Ce 0.98 Mo 0.02 O x catalysts had a distinct vibrational peak near ∼464 cm –1 associated with the F 2g vibrational mode of the cubic fluorite structure. ,, It should also be noted that the vibrational peak near ∼464 cm –1 for the Ce 0.98 Mo 0.02 O x catalyst was weaker and shifted to a lower frequency compared to that of pristine CeO 2 , which may be due to the doping of lighter Mo atoms and subsequent contraction of the CeO 2 lattice . In addition, the vibrational peaks attributed to MoO at 877 and 961 cm –1 for the Ce 0.98 Mo 0.02 O x catalyst indicated the presence of Mo species in the catalyst. , Furthermore, it can be seen from the UV–vis DRS results shown in Figure b that the absorption edge of the Ce 0.98 Mo 0.02 O x catalyst was significantly red-shifted from 442 to 476 cm –1 compared to that of CeO 2 , possibly resulting from the migration of Mo single atoms into the CeO 2 lattice and the stronger interaction between Mo and the CeO 2 matrix, leading to a decrease in symmetry and consequent additional lattice stress. , Such results further confirm the successful doping of the Mo species, which is in good accordance with the results of Raman spectra.…”

“…As shown in Figures S3 and 2a, the Raman spectra indicated that both CeO 2 and Ce 0.98 Mo 0.02 O x catalysts had a distinct vibrational peak near ∼464 cm −1 associated with the F 2g vibrational mode of the cubic fluorite structure. 23,28,29 It should also be noted that the vibrational peak near ∼464 cm −1 for the Ce 0.98 Mo 0.02 O x catalyst was weaker and shifted to a lower frequency compared to that of pristine CeO 2 , which may be due to the doping of lighter Mo atoms and subsequent contraction of the CeO 2 lattice. 30 In addition, the vibrational peaks attributed to Mo�O at 877 and 961 cm −1 for the Ce 0.98 Mo 0.02 O x catalyst indicated the presence of Mo species in the catalyst.…”

“…20−22 A considerable number of studies have reported that the ability of CeO 2 catalysts for the catalytic removal of NO x can be significantly enhanced by optimizing their acidity and redox properties with the assistance of doping with exotic metal atoms. As our previous work 23 reported, the addition of copper cation (Cu δ+ ) into the MoO 3 /CeO 2 catalyst can promote the formation of an active Mo�O structure, which could act as a new Lewis acid site to facilitate the production of coordinated NH 3 . Further experimental investigations revealed that the enhancement of acidity was attributed to the enhanced charge transfer from Mo to Cu.…”

Selective catalytic reduction of NOx with NH3 over copper-based catalysts: recent advances and future prospects

“…Therefore, excellent redox properties and strong acidity are two crucial factors that determine the catalytic performance of catalysts. [27][28][29] In general, the redox properties of catalysts determine the low-temperature activity, while acid properties affect the activity at high temperature. 30,31 In terms of the redox cycle, efficient catalytic performance can be achieved by generating more active NO 3 À , NO ) to participate in the subsequent reaction with activated NO species (nitrates or nitrites species).…”

“…38–40 For the NH 3 -SCR reaction, catalysts such as single metal oxides, mixed metal oxides and supported metal oxides, and pure or metal-exchanged zeolites have consistently demonstrated superior de-NO x performance and N 2 selectivity under oxygen-rich conditions, preventing the formation of secondary pollution in the NH 3 -SCR. 41–45 Different catalysts have been developed to varying degrees because of their different characteristics, which are influenced by multiple effect factors (Fig. 2).…”