A combined DFT calculation and experimental study of the mechanism of the SCR of NO_<i>x</i> by NH₃ over Fe-doped CoMn₂O₄

NH₃ selective catalytic reduction (SCR) is a promising method for NO_<i>x</i> removal, but its low-temperature effectiveness and narrow operating window limit industrial use. This study demonstrates, through DFT calculations and experimental validation, that Fe-doped CoMn₂O₄ (CoFe_0.1Mn_1.9O₄) catalysts can effectively enhance catalytic activity. Through the in-depth study of NH₃-SCR, it was found that the NH₃ adsorption on the catalyst surface might be significantly enhanced by the doping of Fe (<i>E</i>_ads = -1.29 eV → -1.42 eV), and it was also further demonstrated that the NH₃ had a better adsorption energy on the surface of the CoFe_0.1Mn_1.9O₄ catalyst through the electron difference density (EDD) and partial density of states (PDOS). In addition to this, the CoFe_0.1Mn_1.9O₄ catalyst not only reduces the first step of the dehydrogenation reaction of NH₃ (<i>E</i>_α = 0.86 eV → 0.83 eV), but also lowers the energy barrier of the NH₃-SCR (<i>E</i>_α = 1.11 eV → 0.86 eV). All these calculations demonstrate that Fe doping has the potential to significantly enhance catalytic performance. CoMn₂O₄ and Fe-doped CoMn₂O₄ (CoFe_0.02Mn_1.98O₄) catalysts were synthesized using sol-gel and impregnation techniques, respectively. Through characterization and performance testing, CoFe_0.02Mn_1.98O₄ is found to exhibit a more efficient NO_<i>x</i> conversion (87% at 250 °C), and its N₂ selectivity is also slightly improved (64%), which matches with the calculation results. In this study, a method to improve the denitrification efficiency of CoMn₂O₄ spinel catalysts was proposed, which provides a new idea for the development of CoMn₂O₄ catalysts.