Fabrication and Photocatalytic Activity of Single Crystalline TiO2 Hierarchically Structured Microspheres

Single crystalline anatase TiO2 microspheres with co-exposed {001}/{101} facets were prepared by a facile one-pot hydrothermal method using NaF as a morphology controlling agent. The influences of the NaF amount on the morphology and also on the photocatalytic activity were investigated systematically. The obtained microspheres possessed better morphology when the concentration of NaF was chosen at 0.1 mol/L, and the experimental results indicated that the crystal structure and morphology played important roles on the photocatalytic activity, based on the experimental results it was found that the photocatalytic degradation efficiency of TiO2 microspheres on Tetracycline hydrochloride could reach 76.4% in 2 h. Finally, a growth mechanism was proposed by investigating the growth process, i.e., a synergistic effect of F ions modified Ostwald ripening and oriented attachment.

TiO2 nanoflower photocatalysts: Synthesis, modifications and applications in wastewater treatment for removal of emerging organic pollutants

Titanium dioxide (TiO₂) has been considered as one of the most promising photocatalysts nanomaterials and is being used in a variety of fields of energy and environment under sunlight irradiation via photocatalysis. Highly efficient photocatalytic materials require the design of the proper structure with excellent morphology, interfacial structures, optical and surface properties, etc. Which are the key points to realize effective light-harvesting for photocatalytic applications. Hierarchical TiO₂ based nanoflower structures (i.e., 3D nanostructures) possess such characteristics and have attracted much attention in recent years. The uniqueness of TiO₂ nanoflowers (NFs) with a coarse texture and arranged structures demonstrates higher photocatalytic activity. This review deals with the hydrothermal synthesis of 3D TiO₂ NFs and effect of shape/size as well as various key synthesis parameters to improve their optoelectronic and photocatalytic properties. Furthermore, to improve their photocatalytic properties, various strategies such as doping engineering and heterojunction/nanocomposite formation with other functional nanomaterials have been discussed followed by their potential applications in photocatalytic degradation of various emerging pollutants discharged into the wastewater from various sources. Importance of such 3D nanoarchitecutres and future research in other fields of current interest in environments are discussed.

Photocatalytic degradation of lignin by low content g-C3N4 modified TiO2 under visible light

TiO2/g-C3N4 photocatalysts efficiently degraded lignin to obtain small molecule aromatics, which facilitated the efficient utilization of biomass.

Superoxide generated by blue light photocatalysis of g-C3N4/TiO2 for selective conversion of amines

Reactive oxygen species (ROS) are remarkably reactive chemical oxygen-containing molecules that not only occupy critical positions in cell signaling and homeostasis for regulating aerobic living organism's growth and development but also broadly participate in the environmental management as extraordinary oxidizing agents. Inspired by the behaviors of ROS, we designed an artful visible light photocatalytic system for the selective conversion of amines due to the activation of oxygen (O₂) to superoxide (O₂^-) over g-C₃N₄/TiO₂. Here, blue light was manipulated as a light source to circumvent the initiation of the strong nonselective hydroxyl radical (OH) that is often generated by valence band holes (h_vb⁺) of TiO₂. Aerial O₂ was employed to achieve the long-lived, exclusive ROS, O₂^-, while acetonitrile, an aprotic solvent, was utilized to prolong the lifetime of O₂^-. Importantly, the g-C₃N₄/TiO₂ possesses an exceptional capability for the generation of O₂^-. Based on the synergistic effect of two ingredients of the g-C₃N₄/TiO₂ photocatalyst, the highly selective conversion of amines was achieved with superior conversions in comparison with the pristine TiO₂ and g-C₃N₄. Furthermore, a mechanism dominated by O₂^- was proposed according to the kinetic studies, electron paramagnetic resonance (EPR), and ROS quenching experiments. This work highlights the importance of ROS in defining the desirable outcomes over semiconductor photocatalysts.