Improvement of Low-Temperature NH<sub>3</sub>–SCR\nActivity over CeVO<sub>4</sub> Modified by Sm

In\nthis study, the Ce<sub>0.8</sub>Sm<sub>0.2</sub>V catalyst,\nprepared using the coprecipitation method, exhibited excellent NH<sub>3</sub>–SCR activity in a wide temperature range from 175\nto 375 °C, even under a high GHSV of 200,000 h<sup>–1</sup>. Analysis using X-ray diffraction, Raman, and BET techniques revealed\nthat doping Sm into CeVO<sub>4</sub> enlarged the specific surface\narea and reduced the crystallite size of the catalyst. The H<sub>2</sub>-TPR and X-ray photoelectron spectroscopy results indicated that\nthe incorporation of Sm improved the redox ability and enhanced the\ninteraction among Ce, Sm, and V. NH<sub>3</sub>-TPD results demonstrated\nthat introducing Sm into CeVO<sub>4</sub> could increase the number\nof acid sites. All these factors contributed significantly to the\nenhancement of low-temperature NH<sub>3</sub>–SCR activity.\nMoreover, adding Sm could increase the number of Lewis acid sites,\nenhance the adsorption of NO<sub><i>x</i></sub> species,\nand promote the formation of –NH<sub>2</sub> and NH<sub>4</sub>NO<sub>3</sub> species, which play vital roles in enhancing the SCR\nactivity. The NH<sub>3</sub>–SCR reaction on the Ce<sub>0.8</sub>Sm<sub>0.2</sub>V catalyst followed both Langmuir–Hinshelwood\nand Eley–Rideal mechanisms.