In this work, the mesoporous-assembled TiO2 nanocrystals were successfully synthesized by a modified sol-gel process under mild conditions with the aid of glycerol, which is a main by-product from biodiesel production via the transesterification of vegetable oils. The synthesized TiO2 nanocrystals were characterized by various techniques, i.e. N-2 adsorption-desorption, SEM, high resolution TEM, and XRD. The characterization results clearly showed that the glycerol could behave as an efficient mesopore-controlling agent, which induced the mesoporous-assembled characteristic of the synthesized TiO2 nanocrystals with very narrow pore size distribution. The synthesized mesoporous-assembled TiO2 nanocrystals were applied for hydrogen production from the photocatalytic water splitting. The photocatalytic activity results revealed that the synthesized mesoporous-assembled TiO2 nanocrystals possessed much higher hydrogen production activity than the commercially available P-25 TiO2 and ST-01 TiO2 powders. (C) 2011 Elsevier Ltd. All rights reserved.