Ce-doped Mn/Co catalyst: Analysis of performance and mechanism underlying NH3+NO+CO model reaction

Abstract

In this study, we prepared Mn-Co-Ce catalysts through coprecipitation, analyzed their physicochemical properties through X-ray diffraction, transmission electron microscopy, hydrogen temperature programmed reduction, and X-ray photoelectron spectroscopy, and studied the removal of NO by NH3+CO. The Ce-1.25 catalyst (Mn: Co: Ce molar ratio of 1:3:1.25) exhibited the highest NH3+CO synergistic NOx reduction efficiency. Doping of Ce at appropriate concentrations effectively mitigated the micro-agglomeration of metal particles, increasing the relative content of active species on the catalyst surface, providing more defect sites, and enhancing the electron mobility of the adsorbed species and catalyst. The mechanism of the CO-NH3-selective catalytic reduction (SCR) reaction synergy was revealed as follows. The CO-NO reaction involved the gradual deoxidization and reduction process of nitrate; it was difficult for this reaction to be activated in the later stages, which limited its overall activity. The NH3-SCR reaction on the sample surface followed the Langmuir-Hinshelwood mechanism, while CO oxidation and the CO-NO reaction mainly followed the Eley-Rideal mechanism. In the cooperative reaction process, CO mainly reacted with NO3* to generate NO2*, which was accompanied by direct oxidation of some CO.