Visualization of the Formation and 3D Porous Structure of Ag Doped MnO2 Aerogel Monoliths with High Photocatalytic Activity

Owing to their intriguing properties, aerogels with rich and hierarchical pore systems are best appreciated in catalysis, sensing, and separation technologies. Herein, a comprehensive study is presented for inorganic monolithic aerogel of Ag doped MnO2 (Ag-MnO2), synthesized solely out of nanowires of diameter ∼10 nm. We demonstrated a 3D image of the full bulk structure of the aerogel using X-ray computed tomography (μCT), providing a concise and statistical description of its porous structure for the first time. Interestingly, a flow-through supermacroporous system was observed as a result of freeze-drying. Owing to the rich pore system, the Ag-MnO2 aerogel monolith exhibited photocatalytic degradation of organic water pollutants, which was superior in performance as compared to that of the MnO2 powder and compressed Ag-MnO2 pellet. A detailed study of photocatalytic mechanism was also carried out, indicating that Ag can simultaneously modulate the physical and chemical properties of MnO2. This work highlights the significance of porous system in monolith catalysts, and provides insight into design and prepare metal oxide aerogels for environmental and energy applications.