Core-Shell Heterostructured and Visible-Light-Driven Titanoniobate/TiO₂ Composite for Boosting Photodegradation...

Herein, we report a one-dimensional (1D) S-doped K₃Ti₅NbO₁₄@TiO₂ (STNT) core-shell heterostructured composite with an enhanced photocatalytic degradation activity under visible light, which was prepared by a simple reassembly-calcination method using thiourea as the S source. The anisotropically shaped rods are favorable for the rapid transport of photogenerated charge carriers. The substitution of Ti⁴⁺ by S⁶⁺ is primarily incorporated into the lattice of the TiO₂ shell so as to create an intra-band-gap state below the conduction band (CB) position, giving rise to Ti-O-S bonds and thus the visible light response. The presence of electron-deficient S atoms is of benefit to the decreased recombination rate of photogenerated electrons and holes by capturing electrons (e^-). Meanwhile, a tight close interface between K₃Ti₅NbO₁₄ and TiO₂ was formed to achieve a nano-heterojunction structure, leading to the fostered separation of its interfacial photogenerated electrons and holes. The visible-light-driven photocatalytic degradation of methylene blue (MB) by STNT composites is higher than that by pure K₃Ti₅NbO₁₄, owing to the synergistic effects of S doping and heterojunction. A possible photocatalytic mechanism was proposed with a reasonable discussion. This work may provide an insight into constructing highly efficient core-shell photocatalysts used toward sustainable environmental remediation and resource shortages.