In Situ Ti³⁺/N-Codoped Three-Dimensional (3D) Urchinlike Black TiO₂ Architectures as Efficient Visible-Light-Driven Photocatalysts

In situ Ti³⁺/N-codoped 3D urchinlike black TiO₂ (b-N-TiO₂) is synthesized via hydrothermal treatment with an in situ solid-state chemical reduction method, followed by annealing at 350 °C in argon. The results indicate that N and Ti³⁺ was codoped into the lattice of anatase TiO₂. The prepared b-N-TiO₂, with a narrow bandgap of ∼2.43 eV, possesses a three-dimensional (3D) urchinlike nanostructure, which is composed of fiberlike architecture with a length of 200-400 nm and a width of 25 nm. The visible-light-driven photocatalytic degradation rate of Methyl Orange and hydrogen evolution rate for b-N-TiO₂ are 95.2% and 178 μmol h^-1 g^-1, respectively, which are ∼3 and ∼8 times higher than those of pristine TiO₂. The excellent photocatalytic activity is mainly attributed to synergistic effect of the N and Ti³⁺ codoping narrowing the bandgap, and unique 3D urchinlike architecture favors the separation and transport of photogenerated charge carriers and offers more surface-active sites. (Chemical Equation Presented).