Controlled synthesis of Sn-based oxides via a hydrothermal method and their visible light photocatalytic performances

Abstract

Controlled synthesis of Sn-based oxides with a different valence state is still a challenge. Here, we developed a facile hydrothermal method for selective preparation of SnO₂, Sn²⁺ doped SnO₂ (Sn²⁺–SnO₂), and SnO/SnO₂ composites, and SnO with SnCl₂ as a precursor. The valence state of Sn was regulated successively from Sn⁴⁺ to Sn²⁺ through controlling the hydrothermal solution from an O₂-rich to an O₂-deficient atmosphere, which was achieved by adding H₂O₂ or urea into the solution. The structure, absorption, morphology, and the visible light photocatalytic performance of the products were investigated systematically. SnO₂, Sn²⁺–SnO₂, SnO/SnO₂, and SnO could be prepared in a H₂O₂-contained, H₂O, urea-contained, and N₂ purged urea-contained solution, respectively. For Sn²⁺–SnO₂, the doping amount of Sn²⁺ could be further tuned by varying the hydrothermal temperature, while for SnO/SnO₂, the coupling amount of SnO could be controlled by the dosage of urea. Visible-light-induced photocatalytic degradation of methyl orange was achieved successfully on Sn²⁺–SnO₂ and SnO/SnO₂. However, further work is still required to improve the stability of the samples due to vulnerability of Sn²⁺.