Mesoporous yolk–shell SnS2–TiO2 visible photocatalysts with enhanced activity and durability in Cr(vi) reduction†
A novel mesoporous yolk–shell SnS2–TiO2 visible photocatalyst (ST-is) was synthesized by in situ doping TiO2 with SnO2 through solvothermal alcoholysis, followed by sulfurization under hydrothermal conditions. The ST-is displayed higher activity in photocatalytic reduction of Cr(VI) owing to the strong photosensitizing effect of SnS2 in uniform nanoparticles and the enhanced light harvesting via multiple reflections in yolk–shell chambers. Meanwhile, the strong SnS2–TiO2 interaction could generate more heterojunctions which facilitated photoelectron transfer from SnS2 to TiO2, leading to the enhanced activity by inhibiting photoelectron–hole recombination. Moreover, the ST-is displayed strong durability owing to the strong SnS2–TiO2 interaction and the encapsulation of SnS2 nanoparticles in the yolk–shell chamber, which could inhibit SnS2 leaching. Furthermore, because of the electronegative surface and high surface area, the ST-is could thoroughly purify wastewater by completely adsorbing Cr3+ resulting from Cr(VI) reduction. In addition, the presence of photocatalytic degradation of organic compounds promoted Cr(VI) reduction owing to inhibition of photoelectron–hole recombination by consuming holes.