Efficient catalytic removal of airborne ozone under ambient conditions over manganese oxides immobilized on carbon nanotubes

Abstract

Atmospheric ozone pollution presents a new environmental challenge in developing countries such as China. As ozone is a widely used oxidant and a common by product of civil and industrial activities, it is potentially emitted during these activities and causes pollution. Ozone pollution does significant harm to both human health and the ecosystem. Therefore, it is highly desirable to develop efficient methods to eliminate airborne ozone. Catalytic decomposition has attracted extensive interest due to the fast conversion of O₃ to O₂ under ambient conditions. In this study, we fabricated manganese oxides, including MnO_x nanosheets and nanoparticles, immobilized on carbon nanotubes by a facile redox method for the decomposition of ozone. The as-prepared catalysts were characterized by multiple techniques. It was found that the MnO_x nanosheets consisted of amorphous MnO₂ coated on the surface of carbon nanotubes (MnO₂/CNTs), whereas the MnO_x nanoparticles consisted of crystallized Mn₃O₄ immobilized on carbon nanotubes with relatively high dispersion (Mn₃O₄/CNTs). Both catalysts exhibited superior catalytic performance for the decomposition of ozone. Nearly 100% ozone removal efficiency was achieved at the high GHSV of 600 000 mL g_cat⁻¹ h⁻¹ with the ozone concentration of 40 ppm. Moreover, the catalytic activities were maintained even after repeated tests under a high-humidity atmosphere. The large specific surface area and enhanced ability of electron transfer from CNTs to MnO_x were responsible for the excellent catalytic performance of the catalysts towards ozone decomposition.