Macroporous MnO₂-based aerogel crosslinked with cellulose nanofibers for efficient ozone removal under humid...

Atmospheric ozone pollution receives worldwide concerns, and it is a big challenge to search for the practical ozone-decomposition catalyst with good moisture resistance. Herein, a light-weight and high-porosity MnO₂-based hybrid aerogel was synthesized with cellulose nanofibers using a facile ice-template approach, followed by freeze-drying. In the three-dimensional framework, the cellulose nanofibers serve as the skeletons to disperse MnO₂ particles, improving the exposure of active sites on MnO₂. XPS, ¹H NMR and ATR-FTIR demonstrate that MnO₂ particles are effectively combined with cellulose nanofibers through hydrogen bonds, which originate from the abundant surface hydroxyl groups of both components. These consumed surface hydroxyl groups of MnO₂ not only reduce the water adsorption but also avoid the generation of surface-adsorbed H₂O via the reaction with ozone, thus alleviating the catalyst deactivation. In addition, the interconnected macroporous structure enables the rapid diffusion of ozone molecules and facilitates the passage of water molecules, which is conducive to the adsorption and decomposition of ozone on the active sites, i.e. surface oxygen vacancies. Thus, the high and stable ozone conversion was achieved for 150 ppb O₃ under the relative humidity of 50% and the space velocity of 600 L·g^-1·h^-1 within 10 days at room temperature.