Unique 1D/3D K2Ti6O13/TiO2 micro-nano heteroarchitectures: controlled hydrothermal crystal growth and enhanced photocatalytic performance for water purification

Abstract

Semiconductor photocatalysis towards pollutant degradation driven by solar energy is regarded as a promising technology to solve global energy and environmental problems. In this work, three-dimensional (3D) TiO₂ microflowers (MFs) were hybridized with one-dimensional (1D) K₂Ti₆O₁₃ nanobelts (NBs) to construct novel hierarchical Ti–O-based micro-nano heteroarchitectures (HAs) using a controlled hydrothermal route. The well-developed TiO₂ MFs were featured with their petals consisting of several 1D nanostructures with the width of around 100–200 nm. Particularly, the crystal growth mechanism of the unique 1D/3D K₂Ti₆O₁₃/TiO₂ HAs was proposed based on the time-dependent experiments combined with structural and morphological characterizations. Unexpectedly, the optimized K₂Ti₆O₁₃/TiO₂ composites exhibited much higher photocatalytic performance for the degradation of organic dyes and antibiotics under simulated sunlight irradiation, which was more than 2-folds higher than that of single K₂Ti₆O₁₃ and TiO₂ catalysts. Moreover, the photocatalytic activity of K₂Ti₆O₁₃/TiO₂ composites for dye degradation was higher than that of commercial P25 under visible light irradiation (λ > 400 nm). Apart from the advantages of hierarchical micro-nano HAs in improving light adsorption and surface area, the enhanced photocatalytic properties could be particularly attributed to the formation of K₂Ti₆O₁₃/TiO₂ heterojunctions that offered available interfacial channels for charge transfer and separation, as proved by the photoluminescence and photoelectrochemical measurements. Furthermore, good stability and long-term durability of the composite photocatalysts were also determined by cycling tests, mainly resulting from the tightly combined K₂Ti₆O₁₃/TiO₂ heterostructures. This work can be extended to design other hierarchical TiO₂-based micro-nano hybrids with superior photocatalytic properties for environmental purification and solar energy conversion.