Preparation of three-dimensionally ordered macroporous MFe2O4 (M = Co, Ni, Cu) spinel catalyst and its simultaneous catalytic application in CO oxidation and NO plus CO reaction

A series of three-dimensional ordered macroporous (3DOM) MFe2O4 spinel catalysts are synthesized for CO oxidation and selective catalytic reduction of NOx by CO. Co and Ni did not have a good synergy with Fe, respectively, and the reduction performance of the corresponding spinel oxides is also lower than that of pure Fe2O3. However, the introduction of Cu into Fe to form spinel catalysts not only promotes the reduction performance, but also improves the surface active oxygen species, and the optimum CuFe2O4 catalyst has the highest catalytic activity in both reactions. Moreover, the appearance of Cu+-CO species in the reactions is the reason why CuFe2O4 catalyst has better catalytic activity than other catalysts at lower temperature. At the same time, the existence of oxygen vacancies at higher temperatures is conducive to the activation of O-2 molecule in CO oxidation and the dissociation of NO molecule in NO + CO reaction. It is noteworthy that both reactions on CuFe2O4 catalyst follow both Langmuir-Hinshlwood (L-H) and Eley-Rideal (E-R) mechanisms.