Improvement of Low-Temperature NH₃–SCR Activity over CeVO₄ Modified by Sm

In this study, the Ce0.8Sm0.2V catalyst, prepared using the coprecipitation method, exhibited excellent NH3–SCR activity in a wide temperature range from 175 to 375 °C, even under a high GHSV of 200,000 h–1. Analysis using X-ray diffraction, Raman, and BET techniques revealed that doping Sm into CeVO4 enlarged the specific surface area and reduced the crystallite size of the catalyst. The H2-TPR and X-ray photoelectron spectroscopy results indicated that the incorporation of Sm improved the redox ability and enhanced the interaction among Ce, Sm, and V. NH3-TPD results demonstrated that introducing Sm into CeVO4 could increase the number of acid sites. All these factors contributed significantly to the enhancement of low-temperature NH3–SCR activity. Moreover, adding Sm could increase the number of Lewis acid sites, enhance the adsorption of NOx species, and promote the formation of –NH2 and NH4NO3 species, which play vital roles in enhancing the SCR activity. The NH3–SCR reaction on the Ce0.8Sm0.2V catalyst followed both Langmuir–Hinshelwood and Eley–Rideal mechanisms.