Nearly complete photodegradation of azo dyes on flaky ZnO@p-Sn macrosandwich nanocomposites via in-situ dealloying-oxidation strategy

A novel fabrication approach to synthesize the macrosandwich photocatalysts of porous Sn anchored flower-like ZnO nanosheets (ZnO@p-Sn) was proposed via in-situ dealloying-oxidation strategy of immiscible Sn₃₀Zn₇₀ precursor alloy composed of Zn and β-Sn phases in 0.5 M NaOH solution. The redeposited amount of ZnO in ZnO@p-Sn macrosandwich photocatalysts strongly depends on the dealloying potential, and the final structure inherits the initial distribution characteristics of the immiscible precursors. The sample after dealloying at −1.30 V, namely ZnO@p-Sn(−1.30 V), has the best photocatalytic effect on photodegradation of Azo-Dye pollutants beneficial from more abundant ZnO nanosheets with the largest surface area and narrowest bandgap of 3.06 eV. ZnO@p-Sn(−1.30 V) has exceptional universality in the degradation of methylene orange, methylene blue, and Rhodamine-B. The corresponding degradation rates are as high as 96.1 %, 98.9 %, and 97.6 % at 140 min. It is of importance that ZnO@p-Sn(−1.30 V) macrosandwich photocatalysts can effectively degrade Azo-dyes pollutants into pure water and CO₂, and the leftover content of S and N elements are as low as 0.07 % which are close to the clean water. Three-dimensional porous Sn structural both increases the active point and improves the electron-hole separation efficiency, which promotes the photocatalytic process. In-situ dealloying-oxidation strategy of the precise control of the dealloying potential and composite architectures achieves the “water-only” photodegradation of Azo-Dyes by the non-precious metal Sn and ZnO.