Template‐free Scalable Synthesis of Flower‐like Co_3‐<i>x</i>Mn_<i>x</i>O₄ Spinel Catalysts for Toluene Oxidation

Abstract

Abstract The rational design of low‐cost transition metal catalysts that exhibit high activity and selectivity may be the most significantly investigated in heterogeneous catalysis. In this study, Co 3‐ x Mn x O 4 ( x =0.75, 1.0, and 1.5) mixed metal oxides were successfully synthesized by a controlled template‐free autoclave strategy and studied for toluene oxidation. It is found that the Co‐rich sample showed markedly enhanced activity and the 3D dandelion‐like Co 2.25 Mn 0.75 O 4 catalyst exhibited in the highest toluene oxidation rate (8.9 μmol/(g cat s)) and a 100 % toluene conversion at 239 °C. In situ DRIFTS study indicates that toluene was sequentially oxidized to benzyl radical, benzaldehyde, benzene, oxalic acid, and finally to CO 2 and H 2 O. The interaction between Co and Mn, in conjunction with the high concentration of surface oxygen species and rich surface oxygen vacancies, reasonably explains the elevated catalytic activity and thermal stability for toluene oxidation over 3D flower‐like Co 3‐ x Mn x O 4 spinel catalysts.