Nitrogen-doped TiO2 microspheres with hierarchical micro/nanostructures and rich dual-phase junctions for enhanced photocatalytic activity

Abstract

We successfully synthesized microspherical nitrogen-doped TiO₂ with hierarchical nano/microstructures, rich anatase TiO₂–TiO₂(B) phase junctions and a reduced band gap by a facile solvothermal process, followed by a urea-based solid-state reaction. Three kinds of nitrogen species in different doping sites, which can improve the photocatalytic activity and reduce the band gap, were found in the hierarchical nitrogen-doped TiO₂ microspheres. In particular, a suitable amount of nitrogen doping was found to effectively reduce the Ti³⁺ concentration in TiO₂, thus benefiting the photocatalytic reaction by reducing the recombination centers in the photocatalyst. The combination of hierarchical microspherical morphology, the rich phase junctions and narrowed band gap gives nitrogen-doped TiO₂ microspheres remarkably improved photocatalytic activity, compared with commercial mixed-phase TiO₂ (P25) and single-phase anatase-type TiO₂. Furthermore, nitrogen-doped TiO₂ microspheres display reliable photocatalytic performance for multiple cycles. The as-prepared nitrogen-doped TiO₂ microspheres hold promise as efficient photocatalysts for various photocatalytic applications.