Photocatalytic Activity and Electron Storage Capability of TiO₂ Aerogels with an Adjustable Surface Area

Mesoporous TiO₂ aerogels with a surface area larger than 600 m² g^–1 have been prepared via acid-catalyzed sol–gel synthesis and supercritical drying. Varying temperature treatments in air result in changes in the morphology of the aerogels and their specific surface area. Interestingly, the ability to store photogenerated electrons in the surface states of the aerogels upon illumination of dispersions in water–methanol mixtures increases at lower calcination temperatures. Additionally, the extent of electron storage capability also depends on hole scavenger concentration. Increasing the calcination temperature to 500 °C results in a decreased surface area and electron storage capability but increased hydrogen evolution rates. Finally, nitrogen reduction to ammonia in the dark is performed with photogenerated stored electrons in TiO₂ aerogels, separating the charge carrier photogeneration from the dark reduction reaction.