Photocatalytic hydrogen generation and electron storage capability of mesoporous TiO2 aerogels with adjustable surface area

Mesoporous TiO2 aerogels with surface area larger than 600 m2 g-1 have been prepared via acid-catalyzed sol-gel synthesis and supercritical drying. Varying temperature treatment in air results in changes in the morphology of the aerogels and their specific surface area. Increasing the calcination temperature to 500 °C results in decreased surface area, however in strongly increased hydrogen evolution rates in photocatalytic experiments. Moreover, electron storage capabilities of different TiO2 aerogels are investigated. The ability to store photogenerated electrons in the surface states of the aerogels upon illumination of dispersions in water-methanol mixtures increases with lower calcination temperature. Furthermore, the extent of electron storage also depends on hole scavenger concentration. 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.