Enhanced visible light induced photocatalytic activity on the degradation of organic pollutants by SnO nanoparticle decorated hierarchical ZnO nanostructures

Abstract

One (1D) and two-dimensional (2D) nanostructures of zinc oxide and tin oxide (ZnO/SnO) nanocomposites were synthesized by a hydrothermal method using ethylenediamine (EDA) as a capping ligand. The effect of Sn concentration on the morphology of the nanocomposites has been investigated. X-ray diffraction analysis indicated good crystallinity of samples with the presence of both ZnO and SnO phases. The morphological analysis revealed the morphological transformation from ZnO nanorods to ZnO/SnO nanosheets by adding Sn. X-ray photoelectron spectra analyses showed significant peak shift in the electronic state of Zn at the higher concentration of Sn. Elemental mapping results clearly evidenced that both ZnO and SnO moieties were uniformly distributed in the nanosheets. Photocatalytic degradation of methylene blue using as-prepared ZnO/SnO nanocomposites was nine times faster than that of pure ZnO under visible light irradiation. It could be attributed to the formation of a hetero-junction between ZnO and SnO. Our experimental results revealed that photogenerated superoxide (O₂⁻˙) radicals were the main reactive species for the degradation of MB. The maximum degradation efficiency was observed for the sample with 1 wt% of tin chloride, the MB related absorption peak completely disappeared after 6 min of irradiation. ZnO/SnO composites extended the light absorption spectra of ZnO to a visible light region and enhanced the visible light photocatalytic activity.