Influences of urea-glycerol mixtures as mixed mesopore-controlling agents on tailoring physicochemical properties and photocatalytic H_2 production activity of sol-gel-derived mesoporous-assembled TiO_2 nanocrystals

摘要

In this work, the mesoporous-assembled TiO_2 nanocrystal photocatalysts were successfully synthesized by a sol-gel process with the aid of urea-glycerol mixtures used as mixed mesopore-controlling agents. The photocatalytic activity of the synthesized mesoporous-assembled TiO_2 nanocrystal photocatalysts was investigated for hydrogen production from the water splitting reaction using methanol as a hole scavenger under UV light irradiation. The synthesized TiO_2 nanocrystal photocatalysts were systematically characterized by TG-DTA, N_2 adsorption-desorption, SEM, high resolution TEM, and XRD analyses. The characterization results showed that the well-controlled contents of urea and glycerol in a urea-glycerol mixture at 75 mol% urea and 25 mol% glycerol resulted in not only the most highly porous network (i.e. the highest specific surface area and total pore volume, and the smallest mean mesopore diameter), but also the smallest crystallite size of the synthesized TiO_2 nanocrystal photocatalyst. The photocatalytic reaction results, hence, revealed a much superior photocatalytic hydrogen production activity of the mesoporous-assembled TiO_2 nanocrystal synthesized with 75 mol% urea and 25 mol% glycerol to the other synthesized TiO_2 nanocrystals, also being much higher than those of the commercially available P-25 TiO_2 and ST-01 TiO_2 powders.