Accelerated Dual Activation of Lattice Oxygen and Molecule Oxygen over CoMn2O4 Catalysts for VOC Oxidation: Promoting the Role of Oxygen Vacancies

The in-depth activation mechanism of oxygen species (including lattice oxygen and gaseous oxygen) for catalytic oxidation reactions has not been elucidated and still remains a question on the experimental level. In this work, the dual activation of lattice oxygen and molecule oxygen for highly efficient volatile organic compound oxidation was observed on spinel catalysts through the construction of oxygen vacancy engineering (urea modification). The active surface lattice oxygen species were generated via weakening the metal–oxygen bond strength, which could be easily activated to participate in the catalytic oxidation of toluene to form CO2. Simultaneously, the activation ability of gaseous molecular oxygen was also enhanced to promote the replenishment of lattice oxygen species. Moreover, the formation and consumption rates of intermediates could be significantly accelerated due to the dual activation of oxygen species. Hence, the U400 catalyst (T90 = 217 °C) exhibited significantly enhanced catalytic performance for toluene oxidation compared with the pristine catalyst (T90 = 250 °C). This work provided a credible comprehension of the dual activation process of lattice oxygen and molecule oxygen in the heterogeneous catalytic oxidation reaction, which was efficient for developing a pathway to boost the catalytic oxidation activity.