Study on the mechanism of CO oxidation and NO removal by CO-SCR over MFe₂O₄ (M=Co, Cu, Zn)

In this article, density functional theory (DFT) was applied to research the structures of γ-Fe₂O₃ and MFe₂O₄ (M=Co, Cu, Zn) and to optimize the adsorption models of gases such as CO and NO onto the catalysts. Additionally, the study analyzed the CO oxidation reaction on MFe₂O₄ (M=Co, Cu, Zn) and the selective catalytic reduction (SCR) reaction of CO + NO in CuFe₂O₄ and ZnFe₂O₄. Results showed that CO can effectively adsorb on the reactive substrates, reacting with lattice oxygen to produce CO₂ and oxygen vacancies during the CO oxidation process. γ-Fe₂O₃ (001) required an energy of 0.95 eV to complete the reaction, while CuFe₂O₄ (100) needed only 0.33 eV, offering better selectivity. In the reaction of CO + NO on CuFe₂O₄ and ZnFe₂O₄, NO adsorbed on the surface with double oxygen vacancy to form N₂O₂ intermediate, then reacted to produce N₂ and fill the oxygen vacancy. CuFe₂O₄ and ZnFe₂O₄ required energy barriers of 0.68 eV and 0.73 eV, respectively, demonstrating the feasibility of the CO-SCR reaction on the catalyst surface. Further exploration of the reaction in an oxygen-enriched environment found that O₂ can inhibit the CO-SCR reaction. The study reveals that MFe₂O₄ (M=Co, Cu, Zn) catalysts can improve the catalytic activity of the CO oxidation reaction and CO-SCR reaction, with CuFe₂O₄ exhibiting the best selectivity and catalytic activity. What’s more, this study also provides insights for the simultaneous removal of CO and NO.