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

Abstract

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.