Same titanium glycolate precursor but different products: successful synthesis of twinned anatase TiO2 nanocrystals with excellent solar photocatalytic hydrogen evolution capability

Abstract

Exploiting a synthesis protocol to tailor TiO₂ with a unique morphology and crystal phase has received considerable interest in the energy and environmental fields. We here describe the use of a titanium glycolate precursor in a hydrothermal hydrolysis reaction to engineer TiO₂ nanocrystals with different crystal phases and structures. Anatase TiO₂ nanocrystals with twinned structures were obtained by using a lower amount of NaOH in the hydrolysis system, while brookite TiO₂ nanocrystals were formed when higher amounts of NaOH were employed. The as-synthesized different TiO₂ nanocrystals have a suitable bandgap to harvest photons and a more negative bottom level of the conduction band than the redox potential of H⁺/H₂ indicating their potential as hydrogen-evolution semiconductor photocatalysts. However, the TiO₂ nanotwins show promoted charge separation efficiency, and thus result in superior photocatalytic H₂ generation activity compared to the anatase and brookite TiO₂ nanocrystals. Our findings provide an effective and versatile solution for the fabrication of TiO₂-based nanostructures with different phases and morphologies through chemical conversion of powder precursor nanoparticles, which could pave the way to the design of other functional nano-oxides with unique structures.