Water-Catalyzed Low-Temperature Transformation from Amorphous to Semi-Crystalline Phase of Ordered Mesoporous Titania Framework

In this paper, the phase transformation in water at low temperature from amorphous TiO 2 to semi-crystalline anatase is reported. Our approach is an environmentally friendly low energy consumer process that requires no specific devices or instrumentation. The phase transition occurs even at room temperature. However, the higher the temperature is, the better the crystallinity is. Crystallization of amorphous titania occurs through a rearrangement of the TiO 6 2– octahedral units in amorphous TiO 2 . The phase transformation is catalyzed by water, which adsorbs on the titania surface to form bridges between the surface OH groups of different octaedra. The obtained titania samples have been used for the photodegradation of methyl orange. Because of the formation of anatase, mesoporous TiO 2 exhibits a photocatalytic activity after treatment in water. However, the activity is lower than that of the standard photocatalysts because the TiO 2 treated during 1 h in water at 120 °C has degraded 85% of methyl orange within 240 min compared to 45 min for P25.