Fabrication of ordered layered SnO 2 /TiO 2 heterostructures and their photocatalytic performance for methyl blue degradation.

The rapid growth in population and industrialization has given rise to serious environmental issues, especially the water pollution. Photocatalysis with the assist of semiconductor photocatalysts has been considered as an advanced oxidation technique for degrading a variety of pollutants under solar irradiation. In this work, we have fabricated SnO 2 -TiO 2 heterostructures with different ordered layers of SnO 2 and TiO 2 via the sol-gel dip-coating technique and utilized in photocatalysis for degradation of methyl blue dye under UV irradiation. The influence of the layer's position on SnO 2 and TiO 2 properties is investigated via the various techniques. The grazing incidence X-ray diffraction (GIXRD) analysis reveals that the as-prepared films exhibit pure anatase TiO 2 and kesterite SnO 2 phases. The 2SnO 2 /2TiO 2 heterostructure exhibit the maximum crystallite size and smallest deviation from the ideal structure. Scanning electron microscopy cross-section images manifest good adhesion of the layers to each other and to the substrate. Fourier transform infrared spectroscopy reveals the characteristic vibration modes of SnO 2 and TiO 2 phases. UV-visible spectroscopy measurements indicate that all films exhibit high transparency (T = 80%) and the SnO 2 film reveals a direct band gap of 3.6 eV, while the TiO 2 film exhibits an indirect band gap of 2.9 eV. The optimal 2SnO 2 /2TiO 2 heterostructure film revealed best photocatalytic degradation performance and the reaction rate constant for methylene blue solution under UV irradiation. This work will trigger the development of highly efficient heterostructure photocatalysts for environmental remediation.