UV-Visible ار راد ن .د TiO2 ( تیفرظ راون مان هب نورتکلا یاراد یژرنا زارت لماش VB و ) رگید زارت ی یژرنا اب ( ییاناسر راون مان هب نورتکلا زا یلاخ و رتلااب VB یم ) .دشاب ت ود نیا نیب یژرنا توافت یژرنا فاکش زار ، پگ دناب هدیمان یم .دوش هک ینامز زا نورتکلا لاقتنا VB هب VB یم ماجنا دریگ ، TiO2 اب ودح یژرنا بذج د ev 2 / 3 ، نورتکلا تفج کی دیلوت یم هرفح .دیامن و نورتکلا هرفح ی نا اب هدش دیلوت یم کرتشم حطس هب لاقت ثعاب دناوت شنکاو ماجنا اه یی ددرگ . TiO2 دربراک ،دراد یدایز یاه هلمج زا یم ناوت اوه یگدولآ هیفصت یارب (CO2) و بآ و ... نآ زا هدافتسا درک .

Advanced Nanoarchitectures for Solar Photocatalytic Applications

Titanium dioxide (TiO2), as an important semiconductor metal oxide, has been widely investigated in the field of photocatalysis. The properties of TiO2, including its light absorption, charge transport and surface adsorption, are closely related to its defect disorder, which in turn plays a significant role in the photocatalytic performance of TiO2. Among all the defects identified in TiO2, oxygen vacancy is one of the most important and is supposed to be the prevalent defect in many metal oxides, which has been widely investigated both by theoretical calculations and experimental characterizations. Here, we give a short review on the existing strategies for the synthesis of defective TiO2 with oxygen vacancies, and the defect related properties of TiO2 including structural, electronic, optical, dissociative adsorption and reductive properties, which are intimately related to the photocatalytic performance of TiO2. In particular, photocatalytic applications with regard to defective TiO2 are outlined. In addition, we offer some perspectives on the challenge and new direction for future research in this field. We hope that this tutorial minireview would provide some useful contribution to the future design and fabrication of defective semiconductor-based nanomaterials for diverse photocatalytic applications.

Defective TiO2 with oxygen vacancies: synthesis, properties and photocatalytic applications

Since the early development of this technology in the 1970s, TiO2 constitutes the archetypical photocatalyst due to its relatively high efficiency, low cost and availability. However, during the last decade a considerable number of new photocatalytic materials, either semiconductor or not, have been proposed as potential substitutes of TiO2, particularly in the case of solar applications, for which this standard photocatalyst is not very suitable because of its wide band gap. Semiconductors based on cations with d0 configuration such Ta5+ or Nb5+, as well as oxides or nitrides of d10 elements such as Bi3+, In3+ or Ga3+ are among the most successful novel photocatalysts, but non-semiconductor solids like cation-interchanged zeolites also produce interesting results. In addition, some classical semiconductors like ZnO or CdS, initially discarded as a consequence of their poor stability under irradiation, have been reconsidered as feasible photocatalysts for particular applications. This growing body of data requires new analysis of the challenges and opportunities facing photocatalysis in order to assess which of the photoactive materials are best for each particular application. In this review, we summarize, with an historical perspective, the main achievements obtained with photocatalyst alternatives to TiO2 in the three main niches for this technology: water splitting for hydrogen production, decontamination and disinfection processes, and organic synthesis.

Development of alternative photocatalysts to TiO2: Challenges and opportunities

Advanced oxidation processes (AOPs), defined as those technologies that utilize the hydroxyl radical (·OH) for oxidation, have received increasing attention in the research and development of wastewater treatment technologies in the last decades. These processes have been applied successfully for the removal or degradation of toxic pollutants or used as pretreatment to convert recalcitrant pollutants into biodegradable compounds that can then be treated by conventional biological methods. The efficacy of AOPs depends on the generation of reactive free radicals, the most important of which is the hydroxyl radical (·OH). The authors summarize the formation reactions of ·OH and the mechanisms of pollutants degradation. They cover six types of advanced oxidation processes, including radiation, photolysis and photocatalysis, sonolysis, electrochemical oxidation technologies, Fenton-based reactions, and ozone-based processes. Controversial issues in pollutants degradation mechanism were discussed. They review t...

Advanced Oxidation Processes for Wastewater Treatment: Formation of Hydroxyl Radical and Application

Considerable efforts have been devoted to enhancing the photocatalytic activity and solar energy utilization of photocatalysts. The fabrication of type II heterostructures plays an important role in photocatalysts modification and has been extensively studied. In this review, we briefly trace the application of type II heterostructured semiconductors in the area of environmental remediation and water splitting, summarize major fabrication methods, describe some of the progress and resulting achievements, and discuss the future prospects. The scope of this review covers a variety of type II heterostructures, focusing particularly on TiO2 and ZnO based visible light driven type II 0D and 1D heterostructured photocatalysts. Some other low dimensional nanomaterials which have shown high-performance photocatalysis are also presented. We expect this review to provide a guideline for readers to gain a clear picture of fabrication and application of type II heterostructures.

Visible light driven type II heterostructures and their enhanced photocatalysis properties: a review

A nanocrystal heterojunction LaVO4TiO2 visible light photocatalyst has been successfully prepared by a simple coupled method. The catalyst was characterized by powder X-ray diffraction, nitrogen adsorption-desorption, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectra, photoluminescence, and electrochemistry technology.The results showed that the prepared nanocomposite catalysts exhibited strong photocatalytic activity for decomposition of benzene under visible light irradiation with high photochemical stability. The enhanced photocatalytic performance of LaVO4/TiO2 may be attributed to not only the matched band potentials but also interconnected heterojunction of LaVO4 and TiO2 nanoparticles.

Efficient degradation of benzene over LaVO4/TiO2 nanocrystalline heterojunction photocatalyst under visible light irradiation.

ZnIn2S4 microspheres were successfully synthesized by a hydrothermal method. A series of synthesis temperatures from 80 to 200 °C was investigated. The samples were characterized by X-ray diffraction, UV−vis spectroscopy, nitrogen sorption analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy (SEM). The results indicated that the crystalloid structure and optical property of temperature series products were almost the same. The specific surface area (SBET) of ZnIn2S4 products declined with increasing synthesis temperature. The 80 °C sample had the largest SBET (85.53 m2 g−1). SEM images demonstrated that the morphology of ZnIn2S4 was marigold-like microspheres, and the 80 °C sample had a well-proportioned morphology. Several dyes (methyl orange, congo red, and rhodamine B) were applied in the ZnIn2S4 photocatalytic reactivity investigation. It showed efficient visible light photocatalytic degradation of dyes. A liquid chromatogram−mass spectrometer ...

Photocatalytic Degradation of Dyes by ZnIn2S4 Microspheres under Visible Light Irradiation

Porous ZnIn2S4 microspheres have been successfully synthesized by means of a facile thermal solution method at 353 K. This method was a simple route that involved low temperature, no templates, no catalysts, no surfactants, or organic solvents. Scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, nitrogen sorption analysis, and a UV-vis spectrophotometer were used to characterize the products. The results demonstrated that the microspheres, which were composed of many ZnIn2S4 single crystal nanosheets, underwent the Oswald ripening and self-assembly processes. A morphology formation mechanism has been proposed and discussed. The porous ZnIn2S4 product showed an enhancing visible-light photocatalytic activity for methyl orange degradation. The as-grown architectures may have potential applications in solar energy conversion, environmental remediation, and advanced optical/electric nanodevices.

Low-temperature and template-free synthesis of ZnIn2S4 microspheres.

ZnxCd1−xS nanorods were successfully synthesized by microwave method. Characterized by transmission electron microscopy, ZnxCd1−xS samples were composed of a large quantity of homogeneous rods with diameter about 10 nm. The photocatalytic degradation of methyl orange (MO) in the aqueous phase under visible light irradiation (420 nm < λ < 800 nm) was taken as a model reaction. The conversion of MO degradation using Zn0.28Cd0.72S as the photocatalyst was up to 96% after 6 h of irradiation. The separation and identification of degradation products were measured by liquid chromatography mass spectroscopy (LC-MS). After 6 h of irradiation, the intensity of the main absorption peak of MO (m/z = 304) descended in mass spectrum view, while some new peaks of degradation products showed up. From these results of LC-MS analysis, it can be concluded that it was really a photocatalytic degradation process.

Microwave Synthesis of ZnxCd1−xS Nanorods and Their Photocatalytic Activity under Visible Light

A novel photocatalyst CdWO4 was synthesized via a hydrothermal process, and its high photocatalytic activity was revealed. The influence of preparation conditions on crystal structure, optical properties, and photocatalytic activity of CdWO4 catalyst was investigated. The results showed that the sample was irregular short rods with a monoclinic wolframite structure. In photocatalytic performance, CdWO4 showed a good ability toward the photodegradation of methyl orange (MO) and Rhodamine B (RhB). The specimen prepared at pH = 4 through annealing process had the best activity in photodegradation of MO in aqueous solution under UV light irradiation. But there were no obvious differences in activity performance when annealing temperature was below 873 K, indicating that the temperature had little influence on photocatalytic activity of CdWO4.

Wenjuan Zhang

Papers

Efficient degradation of benzene over LaVO4/TiO2 nanocrystalline heterojunction photocatalyst under visible light irradiation.

Photocatalytic Degradation of Dyes by ZnIn2S4 Microspheres under Visible Light Irradiation

Low-temperature and template-free synthesis of ZnIn2S4 microspheres.

Microwave Synthesis of ZnxCd1−xS Nanorods and Their Photocatalytic Activity under Visible Light

A New Photocatalyst CdWO4 Prepared with a Hydrothermal Method