Sisal-like Sn2+ doped ZnO hierarchical structures: synthesis, growth mechanism, and their application in photocatalysis

Abstract

By introducing SnCl₂ into the reaction system, sisal-like Sn doped ZnO hierarchical structures were prepared by a hydrothermal method without employing templates or matrices. Based on the electron microscopy observations, the growth of such hierarchitectures has been proposed to involve self-assembly followed by the Ostwald ripening process. The effects of the reaction time and dosage of SnCl₂ on the morphology, structure, and performance of the samples were systematically investigated. With the increase of the SnCl₂ dosage from 0 to 10 mmol, the band gap value of the as-synthesized samples decreased from 3.14 to 2.73 eV and then increased again to 2.77 eV. The photocatalytic activities of the as-prepared sisal-like Sn doped ZnO hierarchical structures were about 1.64 times higher than that of the pure ZnO samples. The results showed that the photocatalytic activity of ZnO can be improved by appropriate Sn doping. In addition, the sisal-like Sn doped ZnO hierarchical structures were recyclable and showed a very small change in activity after five consecutive cycles, which might be due to their small band gap and large surface area, as well as their unique morphology.