Construction of H₄ K₂ Sn_2- S₄₊ /TiO₂ nanocomposites with enhanced visible light-driven photocatalytic performance

In this paper, a new photocatalyst with TiO₂ nanospheres decorated on ultrathin layered thiostannate H₄ K₂ Sn_2- S₄₊ (X = 0.5-0.6, HKTS) nanosheets was successfully synthesized by a facile solvothermal method combined with the hydrolysis of tetrabutyl titanate and it was denoted as HKTS/TiO₂. By adjusting the content of tetrabutyl titanate, composites with different Sn/Ti molar ratios were prepared. The composites were applied for RhB degradation under visible light irradiation, and the optimum proportion of HKTS/TiO₂ was obtained. The results of X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy confirmed that TiO₂ was successfully decorated on HKTS nanosheets. The combination of TiO₂ and HKTS extended the absorption wavelength of TiO₂ from UV to visible light range, and the separation efficiency of photoexcited electron-hole pairs was also enhanced. The photocatalytic degradation rate of RhB over HKTS/TiO₂-1.0 was almost 97.9% after 60 min illumination, which was higher than those of HKTS and pure TiO₂. The photocatalyst exhibited excellent reusability and stability as the degradation rate of RhB was 95.7% even after three cycles. The photocatalytic mechanism experiment indicated that ·O₂ ^- and h⁺ played a dominant role in the photocatalytic process. All these results indicate that the newly fabricated HKTS/TiO₂ composites provide a high-performance photocatalyst for waste water treatment, and the application of thiostannate can be extended to the field of photocatalytic materials.