Visible light-responsive photocatalytic technology holds great potential in water treatment to enhance purification efficiency, as well as to augment water supply through the safe usage of unconventional water sources. This review summarizes the recent progress in the design and fabrication of visible light-responsive photocatalysts via various synthetic strategies, including the modification of traditional photocatalysts by doping, dye sensitization, or by forming a heterostructure, coupled with π-conjugated architecture, as well as the great efforts made within the exploration of novel visible light-responsive photocatalysts. Background information on the fundamentals of heterogeneous photocatalysis, the pathways of visible light-responsive photocatalysis, and the unique features of visible light-responsive photocatalysts are presented. The photocatalytic properties of the resulting visible light-responsive photocatalysts are also covered in relation to the water treatment, i.e., regarding the photocatalytic degradation of organic compounds and inorganic pollutants, as well as photocatalytic disinfection. Finally, this review concludes with a summary and perspectives on the current challenges faced and new directions in this emerging area of research.

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Recent developments in heterogeneous photocatalytic water treatment using visible light-responsive photocatalysts: a review

One-dimensional TiO2 nanostructured surface heterostructures (1D TiO2NSHs) have been comprehensively studied during the past two decades because of the possible practical applications in various fields, including photocatalysis, dye-sensitized solar cells, sensors, lithium batteries, biomedicine, catalysis, and supercapacitors. Combining extensive advancements in materials science and nanotechnology, a 1D TiO2NSH material with well-controlled size, morphology, and composition has been designed and synthesized. More importantly, its superior properties, including a high aspect ratio structure, chemical stability, large specific surface area, excellent electronic or ionic charge transfer, and a specific interface effect, have attracted a great deal of interest in improving current performance and exploring new applications. In this tutorial review, we introduce the characteristics of 1D TiO2 nanostructures, the design principles for the fabrication of 1D TiO2NSHs, and we also summarize the recent progress in developing synthesis methods and applications of 1D TiO2NSHs in different fields. The relationship between the secondary phase and the 1D TiO2 nanostructure and between the performance in applications and the excellent physical properties of 1D TiO2NSHs are also discussed.

Recent progress in design, synthesis, and applications of one-dimensional TiO2 nanostructured surface heterostructures: a review

Noble metal-based bimetallic nanoparticles: the effect of the structure on the optical, catalytic and photocatalytic properties.

TiO2 semiconductor nanobelts have unique structural and functional properties, which lead to great potential in many fields, including photovoltaics, photocatalysis, energy storage, gas sensors, biosensors, and even biomaterials. A review of synthetic methods, properties, surface modification, and applications of TiO2 nanobelts is presented here. The structural features and basic properties of TiO2 nanobelts are systematically discussed, with the many applications of TiO2 nanobelts in the fields of photocatalysis, solar cells, gas sensors, biosensors, and lithium-ion batteries then introduced. Research efforts that aim to overcome the intrinsic drawbacks of TiO2 nanobelts are also highlighted. These efforts are focused on the rational design and modification of TiO2 nanobelts by doping with heteroatoms and/or forming surface heterostructures, to improve their desirable properties. Subsequently, the various types of surface heterostructures obtained by coupling TiO2 nanobelts with metal and metal oxide nanoparticles, chalcogenides, and conducting polymers are described. Further, the charge separation and electron transfer at the interfaces of these heterostructures are also discussed. These properties are related to improved sensitivity and selectivity for specific gases and biomolecules, as well as enhanced UV and visible light photocatalytic properties. The progress in developments of near-infrared-active photocatalysts based on TiO2 nanobelts is also highlighted. Finally, an outline of important directions of future research into the synthesis, modification, and applications of this unique material is given.

Structure, synthesis, and applications of TiO2 nanobelts.

Semiconductors photocatalyst, applied in the degradation of organic pollutants in water, were summarized due to its durability, low cost, low toxicity, super-hydrophilicity, and remarkable chemical and photochemical stability. Firstly, this paper intensively summarized the photocatalytic activity of single semiconductors photocatalyst. However, single semiconductors photocatalyst showed some drawbacks that is fast recombination of electron/hole, low adsorption about visible light and low surface coverage of photocatalysts. Thus, coupling semiconductors with desirable matching electronic bandgap and doping semiconductor photocatalysts have been discussed detailly. Notably, the Ag-based semiconductor photocatalysts has been highlight. The indicators for evaluating photocatalysis properties including pollution adsorption, kinetic and recyclability were discussed in detail. In addition, the mechanisms of photocatalytic reaction were discussed, which showed the mechanism is redox reaction and the process could degrade a wide range of organic pollutants into easily degradable intermediates or less toxic small molecular substances.

Action and mechanism of semiconductor photocatalysis on degradation of organic pollutants in water treatment: A review

Heterostructures play an important role not only in the manufacture of semiconductor devices, but also in the field of catalysis. Herein, we report the synthesis of PdO/TiO2 and Pd/TiO2 heterostructured nanobelts by means of a simple co-precipitation method, followed by a reduction process using surface-modified TiO2 nanobelts as templates. The as-obtained heterostructures were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and UV/Vis diffuse reflectance spectroscopy. PdO and Pd nanoparticles with a size of about 1.3 and 1.6 nm were assembled uniformly on the surface of TiO2 nanobelts, respectively. Compared with TiO2 nanobelts, PdO/TiO2 and Pd/TiO2 hybrid nanobelts exhibit enhanced photocatalytic activity upon UV and visible-light irradiation. Photoelectrochemical technology was used to study the heterostructure effect on enhanced photocatalytic activity. Our mechanistic investigation revealed that energy-band matching is the major factor in the observed enhancement of photocatalytic activity.

PdO/TiO2 and Pd/TiO2 heterostructured nanobelts with enhanced photocatalytic activity.

https://depts.washington.edu/solgel/documents/pub_docs/journal_docs/2012/12-JCIS-Hong%20Liu-1-s2.0-S0021979712009459-main.pdf

Yu Guan

Papers

PdO/TiO2 and Pd/TiO2 heterostructured nanobelts with enhanced photocatalytic activity.

High ethanol sensitivity of Palladium/TiO2 nanobelt surface heterostructures dominated by enlarged surface area and nano-Schottky junctions

A stable bimetallic Au–Ag/TiO2 nanopaper for aerobic oxidation of benzyl alcohol

Novel bimetallic chalcogenide adsorbents for elemental mercury removal from flue gas: A review