Convenient architectures of Cu2O/SnO2 type II p–n heterojunctions and their application in visible light catalytic degradation of rhodamine B

Abstract

3D hierarchical heterostructures of p-type Cu₂O/n-type SnO₂ were synthesized by impregnating porous SnO₂ nanospheres with different weight percentages of Cu₂O by a simple hydrothermal route. The heterostructures were then evaluated for their photocatalytic performance under visible light irradiation for degradation of rhodamine B (RhB), an organic pollutant. In addition, the effect of varying Cu₂O content, and thereby the composition, morphology and photocatalytic activity of the Cu₂O/SnO₂ nanocomposite were investigated. XRD revealed that the Cu₂O/SnO₂ nanocomposite comprised of cassiterite tetragonal structured SnO₂ and cubic structured Cu₂O. HR-TEM and FE-SEM of the as synthesized nanocomposite indicated nearly monodispersed nanospheres with an average size around 60 nm. A UV-vis absorption edge of the Cu₂O/SnO₂ nanocomposite synthesized in a 1 : 1 ratio was observed at 484 nm (E_g ∼ 2.56 eV) that indicated considerable absorption in the visible region of the solar spectrum. An enhancement in photocatalytic activity was observed with an increase in Cu₂O impregnation and the complete photo-oxidation of RhB was possible with the 1 : 1 mole ratio Cu₂O/SnO₂ nanocomposite in 90 min under optimized conditions. Photocatalytic activity of the Cu₂O/SnO₂ nanocomposite for the degradation of RhB was much higher than that of individual nanoparticles, primarily attributed to the anti-recombination effect of photogenerated electrons and holes at the junction due to formation of p–n heterojunctions. Identification of intermediates and a detailed mechanism of the photo-oxidation process was accomplished by using analytical techniques such as high-performance liquid chromatography [HPLC] and UV-vis diffuse reflectance [DR] spectroscopy.