Enhanced low-temperature catalytic combustion of toluene over Cu and Mn co-modified α-MnO2 with flower spheres

MnO2, MnO2-M and MnO2-CM were successfully obtained by one-pot hydrothermal method using different precursors, and were applied for the catalytic oxidation of toluene. A variety of characterization means were used to precisely define the physicochemical characteristics of these catalysts. The Cu and Mn co-modified MnO2-CM shows a nanosphere morphology which is made of worm-like particles. And it exhibits better low-temperature catalytic oxidation activity, long term activity stability and H2O resistance, in which the temperature of 90% toluene conversion is about 207 oC and the apparent activation energy of MnO2-CM is as low as 31.7 kJ∙mol−1. This is due to the strong interaction between Cu and Mn from the redox coupling reaction (Cu+ + Mn4+ ↔ Cu2+ + Mn3+) that contributes to produce more oxygen vacancies in MnO2-CM to enhance the gaseous oxygen activation and supplement of active oxygen species at low temperature, leading to stronger oxidation ability.