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

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 (lambda > 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.