Photoinduced reactivity of titanium dioxide

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

This paper summarizes recent research dealing with development of titanium dioxide (TiO2) used for environmental applications. TiO2 plays the most important role owing to its excellent chemical and physical properties. However, the TiO2 band edge lies in the UV region that makes them inactive under visible irradiation. In this regard, considerable efforts have been made to increase the visible light activity of TiO2 via the modification of its electronic and optical properties. Doping TiO2 using either anions or cations is one of the typical approaches that has been largely applied. Coupling TiO2 with a narrow bad gap semiconductor (MxOy/TiO2 or MxSy/TiO2) represents another approach. This work aims to encompass the new progress of TiO2 for an efficient application in water and wastewater treatment under visible light, emphasizes the future trends of TiO2 in the environment, and suggests new research directions, including preparation aspects for the development of this promising material.

Modified TiO2 For Environmental Photocatalytic Applications: A Review

Organic dyes are one of the largest groups of pollutants released into wastewaters from textile and other industrial processes. Because of potential toxicity of the dyes and their visibility in surface waters, removal and degradation of organic dyes have been a matter of considerable interest. A wide range of methods have been developed, amongst which the heterogeneous photocatalysis involving titanium dioxide (TiO2) appears to be the most promising technology. This paper presents a critical review of novel achievements in the modification of TiO2 photocatalytic systems aimed at: enhanced TiO2 photocatalytic efficiency; complete mineralization of organic dyes; efficient utilization of visible and/or solar light; stability and reproducibility of the modified TiO2; recycle and reuse in real wastewater treatment.

Tailored titanium dioxide photocatalysts for the degradation of organic dyes in wastewater treatment: A review

Anatase TiO2 nanocrystallines (17–29 nm) were successfully synthesized by the metal–organic chemical vapor deposition method (MOCVD). Moderate manipulation of system parameters of MOCVD can control the particle size. The electro-optical and photocatalytic properties of the synthesized TiO2 nanoparticles were studied along with several commercially available ultra-fine TiO2 particles (e.g., 3.8–5.7 nm). The band gap of the TiO2 crystallines was determined using the transformed diffuse reflectance technique according to the Kubelka–Munk theory. Results showed that the band gap of TiO2 monotonically decreased from 3.239 to 3.173 eV when the particle size decreased from 29 to 17 nm and then increased from 3.173 to 3.289 eV as the particle size decreased from 17 to 3.8 nm. The results of band gap change as a function of particle size agreed well with what was predicted by the Brus’ equation, i.e., the effective mass model (EMM). However, results of the photocatalytic oxidation of 2-chlorophenol (2-CP), showed that the smaller the particle size, the faster the degradation rate. This is attributed in part to the combined effect of band gap change relative to the spectrum of the light source and the specific surface area (or particle size) of the photocatalysts. The change of band gap due to particle size represents only a small optical absorption window with respect to the total spectrum of the light source, i.e., from 380 to 400 nm versus >280 nm. Consequently, the gain in optical property of the larger particles was severely compromised by their decrease in specific surface area. Our results clearly indicated the importance of specific surface area in controlling the photocatalytic reactivity of photocatalysts. Results also showed that the secondary particle size grew with time due mainly to particle aggregation. The photocatalytic rate constants decreased exponentially with increase in primary particle size. Primary particle size alone is able to predict the photocatalytic rate as it is closely related to the electro-optical properties of photocatalysts.

http://www.physics.udel.edu/~ismat/paper1/20063.pdf

Size dependency of nanocrystalline TiO2 on its optical property and photocatalytic reactivity exemplified by 2-chlorophenol

Photocatalytic activity of nanostructured TiO2 thin films prepared by dc magnetron sputtering method

Improvement of photocatalytic activity of TiO2 thin film by Sn ion implantation

Comparison of the photocatalytic activity of TiO2 powder with different particle size

To improve the oxidation behavior of carbon/carbon composites, we developed a multilayer coating system by pack cementation and sol–gel slurry method. The coating consists of a BN–SiC inner dual-layer and a Si3N4–ZrO2–SiO2 outer barrier layer. The coating can effectively protect the C/C composites from oxidizing below 1500 °C. Thermogravimetric analysis shows that the weight loss of the composites is less than 2.40 wt.% after oxidizing at 1400 °C for 220 h. The whole temperature range oxidation resistance can be attributed to the multilayer protection design. The BN–SiC inner dual-layer can cure the cracks by producing borosilicate glass, and the Si3N4–ZrO2–SiO2 outer barrier layer can prevent the formation of cracks and seal the bubbles. The oxidation kinetics of the coated carbon/carbon composites shows that the Arrhenius curve consists of four parts, corresponding to four different oxidation processes and mechanisms in different temperature regions.

T.M Wang

Papers

Photocatalytic activity of nanostructured TiO2 thin films prepared by dc magnetron sputtering method

Improvement of photocatalytic activity of TiO2 thin film by Sn ion implantation

Comparison of the photocatalytic activity of TiO2 powder with different particle size

Anti-oxidation properties of a BN/SiC/Si3N4–ZrO2–SiO2 multilayer coating for carbon/carbon composites

The effects of oxygen plasma radiation on a-C:H films