Insight into efficient pollutant degradation from paramorphic SnO2 hierarchical superstructures

Abstract

Three-dimensional (3D) hierarchical architectures are currently attracting extensive interests owing to their fascinating morphology-dependent properties and potential applications. In this work, we have developed a facile template-free hydrothermal method to synthesize various 3D SnO2 hierarchical superstructures. It is found that the amount of urea, pH value and the pre-oxidation process play a crucial role in the micro/nanostructural evolutions of building blocks and final products. Oriented attachment and self-assembling dual-controlled mechanisms are then proposed to illustrate the formation of 3D hierarchical superstructures. The application in photocatalysis for the degradation of methylene blue (MB) demonstrates that the as-synthesized SnO2 hierarchical superstructures have highly efficient photocatalytic activity for the degradation of organic pollutants. Particularly, the SnO2 hierarchical superstructure constructed by ultrathin nanosheets can degrade 93% of MB within 150 min, which is much higher than that of commercial SnO2 powders. The enhanced photocatalytic performances can be attributed to the high surface-to-volume ratio, the abundant active sites and the efficient separation of photogenerated electrons and holes induced by the unique 3D loose and microporous superstructures. These new insights obtained in this study will be beneficial for the practical applications of oxide semiconductor materials for photocatalytic degradation of organic pollutants.