A combined DFT calculation and experimental study of the mechanism of the SCR of NOx by NH3 over Fe-doped CoMn2O4.

NH3 selective catalytic reduction (SCR) is a promising method for NOx 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 (CoFe0.1Mn1.9O4) 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 (Eads = -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 CoFe0.1Mn1.9O4 catalyst through the electron difference density (EDD) and partial density of states (PDOS). In addition to this, the CoFe0.1Mn1.9O4 catalyst not only reduces the first step of the dehydrogenation reaction of NH3 (Eα = 0.86 eV → 0.83 eV), but also lowers the energy barrier of the NH3-SCR (Eα = 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 (CoFe0.02Mn1.98O4) catalysts were synthesized using sol-gel and impregnation techniques, respectively. Through characterization and performance testing, CoFe0.02Mn1.98O4 is found to exhibit a more efficient NOx 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.