Simple Route to Prepare Composite Nanocellulose Aerogels: A Case of Photocatalytic De-NO_x Materials Application

The preparation of nanocellulose/TiO2-based aerogels for the emission removal of nitrogen oxide (NOx) species (De-NOx action) is proposed here. Using an innovative valorization strategy of agricultural waste valorization, the formulation of hybrid structures was successfully carried out following a simple colloidal route based on a heterocoagulation process between delignified cellulose nanofibers (CNFs) and TiO2 nanoparticles (TiO2 NPs). A facile freeze-drying process allowed shaping composite materials in which the nanocellulose aerogel acts as a 3D support for the photoactive phase. Under light irradiation, all samples showed a positive response to the NO abatement. The best selectivity was observed for the CNF100 sample (82%) which coupled the highest efficiency of 78% for NO removal, allowing us to achieve an outstanding NOx efficiency of 64%, values much higher than those for the TiO2 P25 powder photocatalyst. Not only does the use of cellulose nanofibers as support for TiO2 P25 provide good dispersion of the photocatalytic nanoparticles but also the specific cross-linked structure of the nanocellulose facilitates good contact and transfer of the reactive gas molecules, both increasing the photocatalytic activity.