Boosting catalytic toluene combustion over Mn doped Co3O4 spinel catalysts: Improved mobility of surface oxygen due to formation of Mn-O-Co bonds

Catalytic combustion is considered as the most promising technology for removing VOCs over composite metal oxide catalysts. Herein, Mn doped Co3O4 spinel catalysts (MnaCo1-aOx) like spherical were successfully prepared via solvothermal method, and applied for catalytic toluene combustion. The physical and chemical properties of catalysts were analyzed by various characterization techniques such as XRD, N2 physical-adsorption, SEM, TEM, H2-TPR, O2-TPD, XPS and in-situ DRIFTS. Among these catalysts, Mn0.4Co0.6Ox shows optimal catalytic activity (T50 = 206 °C; T90 = 215 °C) and stability, and it can still maintain good activity even in presence of H2O. The amounts of the surface Co2+, Mn4+and lattice oxygen are improved based on the interaction between Co and Mn ions (Mn3+ + Co3+ → Mn4+ + Co2+), leading to far stronger oxidation ability of catalyst. The formation of the surface Mn-O-Co bonds on spinel catalysts MnaCo1-aOx improves the mobility of surface oxygen. In addition, the catalytic combustion of toluene over these catalysts follows the Mars-van Krevelen mechanism and the surface lattice oxygen plays a crucial role in the cycle of oxygen species based on in-situ DRIFTS results.