Synthesis of tapered tetragonal nanorods of anatase TiO2 with enhanced photocatalytic activity via a sol-hydrothermal process mediated by H2O2 and NH3

In this paper, a series of tapered tetragonal nanorods of anatase TiO2 enclosed by both high-energy {100} and {001} facets and low-energy {101} facets have been fabricated via a facile sol-hydrothermal approach that is free of organic additives and erosive HF reagents. The particle size and morphology could be finely tuned by varying the volume ratio of H2O2 to NH3 added into the reaction system. The experimental results indicate that these two reagents have opposite actions in the growth of the nanorods. The photocatalytic activity of the as-synthesized nanorods towards H-2 evolution from water was investigated among the three typical samples. The highest H-2 evolution rate reaching up to 3.2 mmol h(-1) g(-1) could be achieved for the sample prepared using a mixture of 5 mL of H2O2 and 5 mL of NH3 as reaction media. This rate is about one order of magnitude higher than that of previously reported elongated truncated tetragonal bipyramids and is comparable to that of nanoparticles about 10 nm in size. The increase of photocatalytic activity was ascribed to the synergistic actions of the large surface area, surface heterojunction formed between adjacent high energy {100} or {001} facets and low energy {101} facets and 1.79 eV conduction band energy above the Fermi level