Controllable Synthesis and Tunable Photocatalytic Properties of Ti3+-doped TiO2.

Photocatalysts show great potential in environmental remediation and water splitting using either artificial or natural light. Titanium dioxide (TiO₂)-based photocatalysts are studied most frequently because they are stable, non-toxic, readily available, and highly efficient. However, the relatively wide band gap of TiO₂ significantly limits its use under visible light or solar light. We herein report a facile route for controllable synthesis of Ti³⁺-doped TiO₂ with tunable photocatalytic properties using a hydrothermal method with varying amounts of reductant, i.e., sodium borohydride (NaBH₄). The resulting TiO₂ showed color changes from light yellow, light grey, to dark grey with the increasing amount of NaBH₄. The present method can controllably and effectively reduce Ti⁴⁺ on the surface of TiO₂ and induce partial transformation of anatase TiO₂ to rutile TiO₂, with the evolution of nanoparticles into hierarchical structures attributable to a high pressure and strong alkali environment in the synthesis atmosphere; in this way, the photocatalytic activity of Ti³⁺-doped TiO₂ under visible-light can be tuned. The as-developed strategy may open up a new avenue for designing and functionalizing TiO₂ materials for enhancing visible light absorption, narrowing band gap, and improving photocatalytic activity. [ABSTRACT FROM AUTHOR]