Amorphous MnO2 surviving calcination: an efficient catalyst for ozone decomposition

Abstract

Ozone pollution has aroused worldwide concern for its adverse impact on both the environment and human health. A series of MnO₂ catalysts with different crystallinities were prepared for ozone decomposition. The crystallinity of MnO₂ was regulated by varying the calcination temperature of an amorphous MnO₂. The calcination temperature was confirmed oddly to have a significant effect on the morphology, the textural properties and the surface chemistry of manganese oxides. Both the pristine amorphous MnO₂ and the one calcined at 300 °C (MnO₂-300) exhibited superior catalytic activity for ozone decomposition owing to the abundant surface oxygen vacancies, large specific surface area, and high oxygen mobility, which were derived from the amorphous structure. FTIR and in situ DRIFTS experiments revealed that calcination generated the hydrophobic MnO₂-300, which showed enhanced water resistant ability compared with the pristine amorphous MnO₂, and significantly suspended catalyst deactivation. Moreover, the oxidation state of Mn slightly changed in the used MnO₂-300, further maintaining the high activity. This work may broaden the horizons of designing catalysts with high stability and efficiency for ozone decomposition.