Effects of pH value and hydrothermal treatment on the microstructure and natural-sunlight photocatalytic performance of ZnSn(OH)6 photocatalyst

The ZnSn(OH)6 nanocubes were prepared under different pH (3–12.4) by liquid precipitation, well characterized and further used for wastewater treatment. The results indicated that the ZnSn(OH)6 nanocubes prepared at pH = 11.1 possessed of uniform size distribution and excellent photocatalytic activity, the degradation efficiency to MB reaches 76.3% after 5 h natural sunlight irradiation. Subsequently, the prepared ZnSn(OH)6 nanocubes was further thermal treated (200 °C, 24 h) in four different solvents, containing deionized water, stock solution, mixed solution (Vwater: Vethanol: Vglacial acetic acid = 3:1:1) and ethanol, named as H-1, H-2, H-3 and H-4, respectively. H-2 and H-3 showed superior photocatalytic performance and the removal efficiency of MB improved to be almost 100%, as well as red-shifted light absorption edge and the band gap energies reduced 0.9 and 0.93 eV, respectively. Moreover, free radical capture experiments showed that the h+ and ·O2− are the main active species for the ZnSn(OH)6 nanocubes and H-2, respectively, while all these three ·OH, ·O2− and 1O2 radicals for H-3. Those results suggested that both pH regulation and thermal treatment could efficiently improve the microscopic morphology, crystal structure and photocatalytic activity of the ZnSn(OH)6, which might pave the way for the artful design of other high-performance catalysts.