Flower-like Mn3O4/CeO2 microspheres as an efficient catalyst for diesel soot and CO oxidation: Synergistic effects for enhanced catalytic performance

Abstract

Synergistic composite metal oxides are proven to be impressive materials due to their multi-functionalities across various catalytic applications. In a composite metal oxide, the interfacial chemistry between the components could provide exceptional redox and catalytic properties. In the present manuscript, the fundamental focus is devoted to investigating the interactions between active metal oxides at their interfaces and the catalytic activities towards diesel soot and CO oxidation. A series of flower-like microspheres namely, CeO2, 10%Mn3O4/CeO2, 20%Mn3O4/CeO2, and 40%Mn3O4/CeO2 catalysts were synthesized, where the effect of different Mn3O4 loadings towards soot combustion and CO oxidation were investigated. The characteristic 50% conversion temperature (T50) of catalytic soot oxidation under loose and tight contact conditions for CeO2 microspheres are 502 and 484 °C, respectively. After the integration of Mn3O4 and CeO2, the T50 values were decreased with the lowest values observed for the 20%Mn3O4/CeO2 microspheres (381 and 350 °C). Similarly, 20%Mn3O4/CeO2 microspheres showed T50 value at 103 °C for CO oxidation when compared to pure CeO2 microspheres (216 °C) and Mn3O4 nanoparticles (356 °C). Activation energy values were decreased when the Mn3O4/CeO2 composite used in soot and CO oxidation. The high catalytic activity can be attributed to the strong synergistic interactions between CeO2 and Mn3O4, variable oxidation states, the amount of readily available surface redox active sites and oxygen vacancies. The possible interfacial interaction between CeO2 and Mn3O4 can be exploited to exhibit enhanced surface structural, and redox properties when compared to the pure counterparts. Post-catalytic oxidation analysis confirms the high stability of the Mn3O4/CeO2 composite. The present study points out the vital role of interfacial interactions in composite metal oxides for improving the surface and redox properties, which are important for the development of highly efficient soot and CO oxidation catalysts.