Garden-like perovskite superstructures with enhanced photocatalytic activity

Abstract

By subjecting amorphous flower-like TiO₂ to a facile hydrothermal synthesis in the presence of Sr²⁺, garden-like perovskite SrTiO₃ superstructures were achieved. The amorphous TiO₂ was preformed using ZnO flowers as templates. Different three-dimensional SrTiO₃ architectures were coexisted in the garden, including SrTiO₃ flowers composed of several hollow sword-shaped petals, many sheet-shaped petals or numerous flake-shaped petals, and SrTiO₃ grass consisting of a number of long blades. These SrTiO₃ superstructures were simultaneously grown on fluorine-doped tin oxide (FTO) substrates. On the basis of a comprehensive study on the effects of growth time, temperature, initial concentrations of precursor, and pH, the formation of these various hierarchical architectures was attributed primarily to the dissolution of amorphous TiO₂ and precipitation of perovskite crystals, followed by the Ostwald ripening process of perovskite nanocrystals and self-organization of perovskite building blocks. Interestingly, this approach can be readily extended to create other perovskite structures, including dendritic BaTiO₃ and nest-like CaTiO₃, as well as PbTiO₃ transformed from plate-like pyrochlore Pb₂Ti₂O₆ after post-thermal treatment. Garden-like SrTiO₃ superstructures showed a superior photocatalytic performance when compared to other as-prepared semiconductors and perovskite materials (i.e., ZnO, TiO₂, BaTiO₃, CaTiO₃ and PbTiO₃), probably due to their intrinsic photocatalytic activity and special garden-like features with a coexistence of various structures that significantly facilitated the adsorption and diffusion of methyl blue (MB) molecules and oxygen species in the photochemical reaction of MB degradation.