CeO₂ doping boosted low-temperature NH₃-SCR activity of FeTiO_x catalyst: A microstructure analysis and reaction mechanistic study

Highlights

• CeO₂ doping significantly improved low-temperature NH₃-SCR activity on FeTiO_x.

• The crystallinity of FeTiO_x was decreased dramatically after CeO₂ doping.

• Unique Ce-O-Fe structure in FeCe_0.2TiO_x accounted for its superior redox property.

• Facile activation of NH₃ to-NH₂ on FeCe_0.2TiO_x promoted the DeNO_x efficiency.

Abstract

FeTiO_x has been recognized as an environmental-friendly and cost-effective catalyst for selective catalytic reduction (SCR) of NO_x with NH₃. Aimed at further improving the low-temperature DeNO_x efficiency of FeTiO_x catalyst, a simple strategy of CeO₂ doping was proposed. The low-temperature (<250℃) NH₃-SCR activity of FeTiO_x catalyst could be dramatically enhanced by CeO₂ doping, and the optimal composition of the catalyst was confirmed as FeCe_0.2TiO_x, which performed a NO_x conversion of 90% at ca. 200℃. According to X-ray diffraction (XRD), Raman spectra and X-ray absorption fine structure spectroscopy (XAFS) analysis, FeCe_0.2TiO_x showed low crystallinity, with Fe and Ce species well mixed with each other. Based on the fitting results of extended X-ray absorption fine structure (EXAFS), a unique Ce-O-Fe structure was formed in FeCe_0.2TiO_x catalyst. The well improved specific surface area and the newly formed Ce-O-Fe structure dramatically contributed to the improvement of the redox property of FeCe_0.2TiO_x catalyst, which was well confirmed by H₂-temperature-programmed reduction (H₂-TPR) and in situ XAFS experiments. Such enhanced redox capability could benefit the activation of NO and NH₃ at low temperatures for NO_x removal. The detailed reaction mechanism study further suggested that the facile oxidative dehydrogenation of NH₃ to highly reactive-NH₂ played a key role in enhancing the low-temperature NH₃-SCR performance of FeCe_0.2TiO_x catalyst.

Graphical abstract

Keywords

NH₃-SCR / CeO₂ doping / Low-temperature NO_x removal / Improved redox property / In situ XAFS analysis

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Acknowledgements

F. L. acknowledges Startup Fund from the University of Central Florida (UCF) (USA). S. X. acknowledges the support from the Preeminent Postdoctoral Program (P3) at UCF (USA). H. H. acknowledges the support from the Key Project of National Natural Science Foundation of China (No. 21637005). The authors sincerely thank Prof. Kiyotaka Asakura from Hokkaido University (Japan) and Dr. Yasuhiro Niwa from Institute of Materials Structure Science (IMSS), High Energy Accelerator Research Organization (KEK) (Japan) for the generous help in XAS experiments conducted at Photon Factory, KEK, Japan (No. 2012G537).

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11783-022-1539-2 and is accessible for authorized users.

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