Development of SnO2-SnSe composites for the efficient photocatalytic degradation of methylene blue.

The discharge of toxic industrial effluents into freshwater has a significant impact on both humans and aquatic lives, which needs to be addressed on an urgent basis. SnO2, a wide bandgap material possesses good photocatalytic properties, which can be exploited to degrade organic pollutants. However, there is a need to develop an appropriate strategy to decrease its bandgap and minimize the recombination of charge carriers. For this purpose, we are reporting the synthesis of SnO2/SnSe composites by wet chemical process in various ratios. The as-synthesized samples were analyzed through various characterization techniques. The X-ray diffraction (XRD) patterns confirmed the successful synthesis of tetragonal rutile SnO2 and orthorhombic structure of SnSe. The average crystallite size varied between 25 and 35 nm. UV–visible spectroscopy (UV–vis) confirmed that the bandgap of SnO2 and SnSe was 3.63 eV and 1.21 eV, respectively, whereas the bandgap of composites ranged from 3.47 to 3.03 eV. The FTIR spectrum exhibited absorption peaks at 745 cm−1, 1113 cm−1, and 1381 cm−1 due to the Sn–O–Sn bond and Sn–OH bond vibrations. Whereas the absorption observed at 665 cm−1 is associated with Se–O bond vibration. Raman spectroscopy revealed the bands at 629 cm−1 and 767 cm−1 for the rutile structure of SnO2 and bands at 75 cm−1, and 152 cm−1 are characteristic of SnSe. Scanning electron microscopy (SEM) illustrated the formation of irregular-shaped agglomerated nanoparticles of the prepared materials. Photodegradation of methylene blue (MB) revealed that the composite containing 78% SnO2 and 32% SnSe (denoted as SS-4) was highly an highly effective catalyst and degraded 97.1% of MB in 120 min. The reaction kinetics of the prepared photocatalysts satisfied the Langmuir–Hinshelwood model. [ABSTRACT FROM AUTHOR]