Catalytic soot combustion performance of core-shell Co₃O₄@MnO_x monolithic catalyst

The Co₃O₄@MnO_x monolithic catalyst with nanorod morphology was synthesized on nickel foam by a two-step hydrothermal process and characterized by XRD, EDS-mapping, H₂-TPR, XPS, Raman and Soot-TPR. The catalytic soot combustion activities of the catalysts were investigated in a fixed-bed micro-reactor and the intrinsic activities of the catalysts were investigated by the isothermal kinetic experiments. The results reveal that the Co₃O₄@MnO_x catalyst shows a core-shell structure with Co₃O₄ as the core and MnO_x as the shell. Compared with Co-NW, there exist more high-valent state species of Mn⁴⁺ and Mn³⁺ and oxygen vacancies on the Co₃O₄@MnO_x catalyst surface due to the interaction between Co₃O₄ and MnO_x, which improve the redox performance of Co₃O₄@MnO_x. Compared with Co-NW, the active oxygen species amount of Co₃O₄@MnO_x is increased by two times, and Co₃O₄@MnO_x shows enhanced activity, which lowers the ignition temperature by 148 ℃ in the presence of NO. Also, compared with Co-NW, Co₃O₄@MnO_x decreases the activation energy of soot combustion reaction from 113.6 to 102.2 kJ/mol, and its intrinsic activity is increased by two times.