Shape dependence structural, optical and photocatalytic properties of TiO2 nanocrystals for enhanced hydrogen production via glycerol reforming

- Effects of different shapes of TiO2 on photocatalytic H2 production were investigated.
- Highest H2 production rate was obtained over TNT as compared to other shapes of TNR and TNS.
- Shape-dependent optical property, active sites lead to superior photocatalytic performance.

Herein, we demonstrate the effect of TiO2 nanocrystals shapes on the structural, optical and photocatalytic properties for solar hydrogen (H2) production in aqueous glycerol solution. Titanium dioxide (TiO2) with different shapes such as nanotubes (TNT), nanorods (TNR) and nanosquares (TNS) were chosen and their photocatalytic performances were evaluated under similar conditions. It was observed that the TNT photocatalyst showed 1.5 and 2.0 folds enhanced H2 production rate compared to TNR and TNS photocatalysts. Glycerol in water undergoes direct oxidation with in-situ generated holes to produce H+ in aqueous solution which in-turn accepts pair of electrons to generate H2 gas only. The catalytic performance is in good correspondence with the photocurrent density of the respective nanostructures in the following order TNT>TNR>TNS. The BET surface area of TNT displayed the improved adsorption of glycerol and its intermediates as compared to other catalysts. Thus, the enhanced photocatalytic activity of TNT was attributed to its synergistic properties owing to their peculiar one dimensional (1-D) nanotubular shape with active sites both interior and exterior surfaces. It enhanced the electron-pair lifetime and more efficient charge separation in TNT compared to TNR and TNS.

Titanium dioxide (TiO2) with different structural morphologies such as nanotubes, nanorods and nanosquares in the absence of any co-catalyst were tested and the photocatalytic performances of nanotubes were 1.5 and 2.0 folds enhanced rate of H2 production as compared to nanorods and nanosquares photocatalysts.266