Titania is one of the most widely used benchmark standard photocatalysts in the field of environmental applications. However, the large band gap of titania and massive recombination of photogenerated charge carriers limit its overall photocatalytic efficiency. The former can be overcome by modifying the electronic band structure of titania including various strategies like coupling with a narrow band gap semiconductor, metal ion/nonmetal ion doping, codoping with two or more foreign ions, surface sensitization by organic dyes or metal complexes, and noble metal deposition. The latter can be corrected by changing the surface properties of titania by fluorination or sulfation or by the addition of suitable electron acceptors besides molecular oxygen in the reaction medium. This review encompasses several advancements made in these aspects, and also some of the new physical insights related to the charge transfer events like charge carrier generation, trapping, detrapping, and their transfer to surface are d...

Review on Modified TiO2 Photocatalysis under UV/Visible Light: Selected Results and Related Mechanisms on Interfacial Charge Carrier Transfer Dynamics

Recent advances in nanostructured materials have been led by the development of new synthetic methods that provide control over size, morphology, and nano/microstructure. The utilization of high intensity ultrasound offers a facile, versatile synthetic tool for nanostructured materials that are often unavailable by conventional methods. The primary physical phenomena associated with ultrasound that are relevant to materials synthesis are cavitation and nebulization. Acoustic cavitation (the formation, growth, and implosive collapse of bubbles in a liquid) creates extreme conditions inside the collapsing bubble and serves as the origin of most sonochemical phenomena in liquids or liquid-solid slurries. Nebulization (the creation of mist from ultrasound passing through a liquid and impinging on a liquid-gas interface) is the basis for ultrasonic spray pyrolysis (USP) with subsequent reactions occurring in the heated droplets of the mist. In both cases, we have examples of phase-separated attoliter microreactors: for sonochemistry, it is a hot gas inside bubbles isolated from one another in a liquid, while for USP it is hot droplets isolated from one another in a gas. Cavitation-induced sonochemistry provides a unique interaction between energy and matter, with hot spots inside the bubbles of approximately 5000 K, pressures of approximately 1000 bar, heating and cooling rates of >10(10) K s(-1); these extraordinary conditions permit access to a range of chemical reaction space normally not accessible, which allows for the synthesis of a wide variety of unusual nanostructured materials. Complementary to cavitational chemistry, the microdroplet reactors created by USP facilitate the formation of a wide range of nanocomposites. In this review, we summarize the fundamental principles of both synthetic methods and recent development in the applications of ultrasound in nanostructured materials synthesis.

Applications of Ultrasound to the Synthesis of Nanostructured Materials

Photocatalysis is a promising and ideal technology to utilize solar energy for energy regeneration and environmental remediation. Photocatalysis based on metal-organic frameworks (MOFs) has attracted extensive attention because of their excellent properties such as tunable structure and optical properties. This review principally summarizes the progress of various modification strategies, including decoration of organic linker or metal center, combination with semiconductors and metal nanoparticles loading. applied to different MOFs (mainly UiOs, MILs, and ZIFs), and their specific applications were summarized as well. In addition, the existing problems and the development prospect of MOFs for photocatalysis were also presented.

Modified metal-organic frameworks as photocatalysts

https://pubs.rsc.org/en/content/articlepdf/2015/cc/c5cc90254a

Introduction of a mediator for enhancing photocatalytic performance via post-synthetic metal exchange in metal–organic frameworks (MOFs)

Photocatalytic materials and technologies for air purification.

A series of Ti1-xZrxO2 solid solutions photocatalysts (x = 0.000, 0.045, 0.090, 0.135, and 0.180) was directly obtained by an ultrasonic spray pyrolysis method. Compared with previous methods for solid solutions, our preparation was very fast. The resulting samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, nitrogen adsorption, and UV−vis diffuse reflectance spectroscopy. The characterizations revealed core−shell spherical structures of the resulting solid solutions. We evaluated photocatalytic activities of the solid solutions on degradation of rhodamine B in aqueous solution under simulated solar light. It was found that Ti0.91Zr0.09O2 solid solution exhibited the highest photocatalytic activity among all the as-prepared samples. Its activity was much higher than that of P25. The formation mechanism of core−shell spherical structures was proposed. Moreover, we successfully extended this method...

Zhi Zheng

Papers

Core−Shell Microspherical Ti1-xZrxO2 Solid Solution Photocatalysts Directly from Ultrasonic Spray Pyrolysis