Hydrothermal synthesis of (Fe,N) co-doped TiO<Subscript>2</Subscript> powders and their photocatalytic properties under visible light irradiation

(Fe, N) co-doped titanium dioxide powders have been prepared by a quick, low-temperature hydrothermal method using TiOSO₄, CO(NH₂)₂, Fe(NO₃)₃, and CN₃H₅ · HCl as starting materials. The synthesized powders were characterized by XRD, TEM, BET, XPS, and UV–Vis spectroscopy. Experimental results show that the as-synthesized TiO₂ powders are present as the anatase phase and that the N and Fe ions have been doped into the TiO₂ lattice. The specific surface area of the powders is 167.8 m²/g by the BET method and the mean grain size is about 11 nm, calculated by Scherrer’s formula. UV–Vis absorption spectra show that the edge of the photon absorption has been red-shifted up to 605 nm. The doped titanium dioxide powders had excellent photocatalytic activity during the process of photo-degradation of formaldehyde and some TVOC gases under visible light irradiation.     

Visible light active anion codoped sol gel titania photocatalyst for pollutant degradation

The photocatalytic activity of carbon and nitrogen co-doped sol gel TiO₂ is tested using methyleneblue degradation and it is found that the activity drops sharply with increase in calcination temperature. The system calcined at 300 °C was found to be the most efficient in dye degradation and can be considered as a good candidate for the future photocatalytic applications. This highly active anion doped TiO₂ is found to show amorphous nature. Elemental analysis reveals the co existence of C and N dopants, which may be responsible for the high efficiency of the catalyst. Visible absorbance is evident from the UV–VIS Diffuse Reflectance Spectra. The N₂ adsorption desorption studies show the H1 hysteresis loops and a well defined mesoporous nature is observed for the catalytic systems prepared in the presence of urea. XPS analysis indicates the presence of Ti–C and Ti–N bonds which are responsible for the visible light activity of the photocatalysts.     

Investigation of Br–N Co-doped TiO<Subscript>2</Subscript> photocatalysts: preparation and photocatalytic activities under visible light

Bromine (Br) and nitrogen (N) co-doped TiO₂ ((Br–N–TiO₂) photocatalysts were prepared by a sol–gel method. The catalysts were characterized by X-ray Diffraction (XRD), N₂ adsorption and desorption isotherms, X-ray Photoelectron Spectra (XPS), UV-Vis Diffraction Spectra and Electron Spin Response (ESR) Spectra. Experiments on photodegradation of Methylene Blue (MB) and Sulfosalicylic Acid (SSA) under visible light were carried out to evaluate the photocatalytic activities of the catalysts. Chemical Oxygen Demand (COD) analysis was also conducted to evaluate the mineralization degrees of the catalysts in MB photodegradation. Enhanced photocatalytic activities were observed for the Br–N–TiO₂ catalysts in the experiments of MB and SSA photodegradation. A possible mechanism was proposed to explain the improved photocatalytic activities of the Br–N–TiO₂ catalysts.     

Phosphorous,nitrogen, and molybdenum ternary co-doped TiO2: preparation and photocatalytic activities under visible light

P, N, and Mo ternary co-doped nano TiO₂ photocatalysts ((P, N, Mo)-TiO₂) were prepared by a single step sol–gel method, which show much enhanced photocatalytic activities over Mo-TiO₂, (P, N)-TiO₂, un-doped TiO₂ and Degussa P25 under visible light irradiation. The degradation rate of 0.72Mo–P-TiO₂ is as high as 65.3%, which is about 6.7 times of that of Degussa P25. Possible reasons for the improvement of photocatalytic activities were analyzed.     

生物质C-N-P自掺杂TiO_2的合成及其对亚甲基兰的光催化降解活性

采用溶胶-超声辐照技术同步合成了生物质C-N-P自掺杂TiO_2复合催化剂,通过X射线光电子能谱(XPS)、X射线衍射(XRD)、扫描电子显微镜(FESEM)、紫外-可见漫反射光谱(UV-Vis-DRS)及光致发光光谱(PL)对样品进行了表征.以亚甲基兰(MB)为目标污染物,研究了C-N-P共掺杂TiO_2的可见光光催化性能.实验结果表明,在可见光照射下,光催化反应时间为2 h时,C-N-P共掺杂TiO_2复合催化剂对亚甲基兰的降解效率最高可达9 8.5%;相比纯TiO_2,C-N-P共掺杂TiO_2复合催化剂的比表面积增大,吸收边带红移,禁带宽度减小,相变温度升高,光生载流子复合率降低.     

Effect of Erbium on the Photocatalytic Activity of TiO2/Ag Nanocomposites under Visible Light Irradiation

Erbium co‐doped TiO₂/Ag catalysts are synthesized by using a simple, one‐step solvothermal method and characterized by X‐ray diffraction, field‐emission scanning electron microscopy, transmission electron microscopy, Raman analysis, X‐ray photoelectron spectroscopy, and diffuse reflectance spectroscopy. The catalysts exhibit anatase crystal structures with increased visible light absorption compared with pure TiO₂. Enhanced photocatalytic activity is observed with Er co‐doped TiO₂/Ag nanocomposites for Rhodamine B degradation under visible light irradiation. The photocatalytic activity of 1 % Er co‐doped TiO₂/Ag is much higher than that of TiO₂/Ag, TiO₂/Er, pure TiO₂, and commercial Degussa P25. The kinetics of the degradation process are studied and the pseudo‐first‐order rate constant (k) and half‐life time (t_1/2) of the reaction are calculated. The enhanced activity might be accredited to the efficient separation of electron–hole pairs by silver and higher visible light absorption of TiO₂ induced by Er.     

Facile preparation of visible-light-sensitive sulfur–nitrogen-codoped titanium dioxide

S–N-codoped TiO₂ powders have been synthesized through a facile one-step sol–gel method by using tetrabutyltitanate and thiourea as precursors. The S–N-codoped TiO₂ treated at 500 °C showed the highest photocatalytic activity for degrading methylene blue under visible light irradiation. XRD, XPS and UV–vis studies revealed that the high visible-light photocatalytic activity of the doped TiO₂ may originate from the synergetic effect of sulfur and nitrogen codoping into TiO₂.     

Synthesis of Fe<Superscript>3+</Superscript> doped ordered mesoporous TiO<Subscript>2</Subscript> with enhanced visible light photocatalytic activity and highly crystallized anatase wall

Fe³⁺ doped mesoporous TiO₂ with ordered mesoporous structure were successfully prepared by the solvent evaporation-induced self-assembly process using P123 as soft template. The properties and structure of Fe³⁺ doped mesoporous TiO₂ were characterized by means of XRD, EPR, BET, TEM, and UV–vis absorption spectra. The characteristic results clearly show that the amount of Fe³⁺ dopant affects the mesoporous structure as well as the visible light absorption of the catalysts. The photocatalytic activity of the prepared mesoporous TiO₂ was evaluated from an analysis of the photodegradation of methyl orange under visible light irradiation. The results indicate that the sample of 0.50%Fe–MTiO₂ exhibits the highest visible light photocatalytic activity compared with other catalysts.     

Nitrogen-doped TiO<Subscript>2</Subscript> nanopowders prepared by chemical vapor synthesis: band structure and photocatalytic activity under visible light

During chemical vapor synthesis of TiO₂ nanopowders, nitrogen atoms were doped into the crystal lattice of TiO₂. The nitrogen atoms were predominantly incorporated substitutionally in the crystal lattice of TiO₂ nanopowders up to the doping level of 1.25 mol% nitrogen, whereas they were in both interstitial and substitutional sites over about 1.43 mol% nitrogen. From the photocatalytic activity of nitrogen-doped TiO₂ estimated by decomposition of methylene blue under visible light, it was found that the substitutional nitrogen anions appearing at the low level doping was beneficial to its photocatalytic activity, whereas the interstitial ones appearing at the high level doping over 1.25 mol% nitrogen were not. The improved photocatalytic activity due to the substitutionally doped nitrogen was attributed to band gap narrowing which was confirmed by the studies of XPS, near edge X-ray absorption fine structure, and UV–Vis absorption.     

Understanding the synergistic effects,optical and electronic properties of ternary Fe/C/S‐doped TiO2 anatase within the DFT + U approach

Although TiO₂ is an efficient photocatalyst, its large band gap limits its photocatalytic activity only to the ultraviolet region. An experimentally synthesized ternary Fe/C/S‐doped TiO₂ anatase showed improved visible light photocatalytic activity. However, a theoretical study of the underlying mechanism of the enhanced photocatalytic activity and the interaction of ternary Fe/C/S‐doped TiO₂ has not yet been investigated. In this study, the defect formation energy, electronic structure and optical property of TiO₂ doped with Fe, C, and S are investigated in detail using the density functional theory + U method. The calculated band gap (3.21 eV) of TiO₂ anatase agree well with the experimental band gap (3.20 eV). The defect formation energy shows that the co‐ and ternary‐doped systems are thermodynamically favorable under oxygen‐rich condition. Compared to the undoped TiO₂, the absorption edge of the mono‐, co‐, and ternary‐doped TiO₂ is significantly enhanced in the visible light region. We have shown that ternary doping with C, S, and Fe induces a clean band structure without any impurity states. Moreover, the ternary Fe/C/S‐doped TiO₂ exhibit an enhanced photocatalytic activity, a smaller band gap and negative formation energy compared to the mono‐ and co‐doped systems. Moreover, the band edges of Fe/C/S‐doped TiO₂ align well with the redox potentials of water, which shows that the ternary Fe/C/S‐doped TiO₂ is promising photocatalysts to split water into hydrogen and oxygen. These findings rationalize the available experimental results and can assist the design of TiO₂‐based photocatalyst materials.     

Preparation,Characterization and Photocatalytic Activity of Fe,La Co-doped Nanometer Titanium Dioxide Photocatalysts

A series of photocatalysts of un-doped, single-doped and co-doped nanometer titanium diox-ide (TiO₂) have been successfully prepared by template method using Fe(NO₃)₃·9H₂O, La(NO₃)₃·6H₂O, and tetrabutyl titanate as precursors and glucan as template. Scanning electron microscopy, X-ray diffraction, and N₂ adsorption-desorption measurement were em-ployed to characterize the morphology, crystal structure and surface structure of the samples. The photo-absorbance of the obtained catalysts was measured by UV-Vis absorption spec-troscopy, and the photocatalytic activities of the prepared samples under UV and visible light were estimated by measuring the degradation rate of methyl orange in an aqueous solu-tion. The characterizations indicated that the prepared photocatalysts consisted of anatase phase and possessed high surface area of ca. 163-176 m²/g. It was shown that the Fe and La co-doped nano-TiO₂ could be activated by visible light and could thus be used as an effective catalyst in photo-oxidation reactions. The synergistic effect of Fe and La co-doping played an important role in improving the photocatalytic activity. In addition, the possibil-ity of cyclic usage of co-doped nano-TiO₂ was also confirmed, the photocatalytic activity of codoped nano-TiO₂ remained above 89.6% of the fresh sample after being used four times.     

Sol–gel synthesized vanadium doped TiO2 photocatalyst: physicochemical properties and visible light photocatalytic studies

Vanadium doped titanium dioxide (V–TiO₂) photocatalyst was synthesized by the sol–gel method using ammonium vanadate as vanadium source. The prepared samples were characterized by XRD, N₂ adsorption–desorption method, UV–Vis DRS, Fourier transform infrared (FTIR), scanning electron microscope–energy dispersive X-ray and photoluminescence (PL) analysis. The results show that V⁵⁺ ions were successfully incorporated into the crystal lattice of TiO₂ as a consequence, not only an obvious decrease in the band gap and a red shift of the absorption threshold into the visible light region was recorded for the V modified TiO₂, but, also a decrease in photogenerated electrons and holes recombination rate was observed as demonstrated by PL analysis. FTIR study indicated that in undoped TiO₂ sample the acetate group favored a bidentate bridging mode of binding with titanium atoms, whereas a bidentate chelating mode of linkage was observed in V–TiO₂ powders. The crystallite size of the samples calcined at 300 and 500 °C were decreased beyond the molar ratio of 200:1 (V:Ti), this may be due to dopant presence in the grain boundaries hindering the crystal growth. The photocatalytic activities for both pure and vanadium doped TiO₂ powders were tested in the discoloration of a reactive dyestuff, methylene blue, under visible light. The 100:1 (V:Ti) doped photocatalyst, calcined at 300 °C showed enhanced photocatalytic activity under visible light with a rate constant (k_obs) of 5.024 × 10^?3 min^?1 which is nearly five times higher than that of pure TiO₂, as result of low band gap value, high specific surface area and a decrease in recombination rate.     

Zr离子掺杂TiO2可见光催化剂光催化活性的研究

本文采用溶胶-凝胶法制备了Zr离子掺杂TiO₂光催化剂。光催化降解对氯苯酚实验表明,Zr离子掺杂浓度为10%时活性最高,其紫外光、可见光催化活性分别是纯TiO₂的1.5倍和4倍。利用XRD、Raman、XPS、UV-Vis DRS、PL等技术对样品进行了表征,结果表明：Zr离子以取代式掺杂方式进入TiO₂晶格,在TiO₂导带下方形成掺杂能级,增强了可见光响应,促进了光生载流子的分离,此外Zr离子掺杂在催化剂表面引入大量表面缺陷,增加了表面羟基物种,从而使得Zr离子掺杂TiO₂光催化剂的紫外、可见光催化活性显著提高。     

Novel sol–gel synthesis of N-doped TiO<Subscript>2</Subscript> hollow spheres with high photocatalytic activity under visible light

Novel ammonia and triethanolamine assisted sol–gel synthesis method was developed to fabricate the N-doped TiO₂ hollow spheres. The prepared hollow spheres were in submicron size and had good morphology and high specific surface area. Polystyrene (PS) latexes in size of 470 nm were used as the templates to fabricate PS/TiO₂ core–shell spheres. Here ammonia and triethanolamine was first employed together to control the sol–gel process. The N-doped TiO₂ hollow spheres were got after calcinations of the core–shell spheres by using triethanolamine as N source, and the amount of doped N could be easily adjusted by changing the amount of triethanolamine. The hollow spheres had distinct visible light response, and the optical response shifted more to the visible region as the amount of doped N increases. The photodegradation of methylene blue expressed the high photocatalytic activity of the N-doped TiO₂ hollow spheres under visible light.     

Synthesis of iron-containing nitrogen-doped titania by hydrothermal method and its photocatalytic activity

By a hydrothermal method, iron and nitrogen co-doped TiO₂ and iron oxide impregnated nitrogen-doped TiO₂ were prepared. The obtained Fe and N co-doped TiO₂ showed mixed anatase, rutile, and brookite phases, and high specific surface areas above 160 m²/g. The Fe co-doping was proved to be effective to enhance the visible light absorption ability; however, the photocatalytic activity in deNO _x experiment decreased due to the increase in the amount of lattice vacancy. On the other hand, the photocatalytic activity of N-doped TiO₂ was improved by the impregnation of iron oxide.     

Preparation, characterization and photocatalytic activity of visible light driven chlorine-doped TiO2

A novel chlorine-doped titanium dioxide catalyst with visible light response was prepared by hydrolysis of tetrabutyl titanate in hydrochloric acid. The catalyst samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). Results showed that the doped element of Cl lowered the temperatures of phase transformation of TiO₂ from amorphous to anatase and from anatase to rutile. The absorption edge of chlorine-doped TiO₂ calcined at 300°C shifted to visible light region. X-ray photoelectron spectroscopy results proved that chlorine existed in the TiO₂ crystal lattice as anion. The photocatalytic degradation of phenol showed that under visible light (λ > 400 nm) irradiation, the chlorine-doped TiO₂ calcined at 300°C displayed the best performance, the degradation ratio of phenol was 42.5% after 120 min. Translated from Chinese Journal of Catalysis, 2006, 27(10): 890–894 [译自: 催化学报]     

Synthesis and characterization of novel InVO<Subscript>4</Subscript>–TiO<Subscript>2</Subscript> thin films using the low temperature sol

The InVO₄ sol was obtained by a mild hydrothermal treatment (the precursor precipitation solution at 423 K, for 4 h). Novel visible-light activated photocatalytic InVO₄–TiO₂ thin films were synthesized through a sol–gel dipping method from the composite sol, which was obtained by mixing the low temperature InVO₄ sol and TiO₂ sol. The photocatalytic activities of the new InVO₄–TiO₂ thin films under visible light irradiation were investigated by the photocatalytic discoloration of methyl orange aqueous solution. The thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and UV–Vis absorption spectroscopy (UV–Vis). The results revealed that the InVO₄ doped thin films enhanced the methyl orange degradation rate under visible light irradiation, 3.0 wt% InVO₄–TiO₂ thin films reaching 80.1% after irradiated for 15 h.     

Sol–gel preparation of pure and doped TiO2 films for the photocatalytic oxidation of ethanol in air

Stable sols of TiO₂ were synthesized by a non-aqueous sol–gel process using titanium (IV) isopropoxide as precursor. The microstructure, optical and morphological properties of the films obtained by spin-coating from the sol, and annealed at different temperatures, were investigated using scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy and ellipsometry. The crystalline structure of the films was characterized by X-ray diffraction and their photocatalytic activity was evaluated for the oxidation of ethanol in air. The influence of the calcination temperature, pre-heat treatment and the number of layers was studied. Simultaneous thermo-gravimetric and differential thermal analysis measurements were carried out to ascertain the thermal decomposition behavior of the precursors. In order to obtain a higher photoresponse in the visible region, a series of vanadium-, niobium- and tantalum-doped TiO₂ catalysts was synthesized by the same sol–gel method. For V doping two different precursors, a vanadium alkoxide and V₂O₅, were used. The effect on the crystallization and photocatalytic activity of the doped TiO₂ films was investigated. Furthermore, to identify the effective composition of the samples, they were characterized by X-ray photoelectron spectroscopy and the surface area of the powders was measured by N₂ adsorption. The 10 wt.% doped catalysts exhibit high photocatalytic activity under visible light and among them the best performance was obtained for the sample containing Ta as dopant. The crystallite sizes are closely related to the photocatalytic activity.     

Synthesis and photocatalytic activity of nanocrystalline TiO2 co-doped with nitrogen and cobalt(II)

Nitrogen-modified cobalt-doped TiO₂ materials were successfully prepared via a modified sol–gel method. The structure and properties of the catalysts were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM, ultraviolet–visible light diffuse reflectance spectra (UV–Vis DRS), N₂ adsorption–desorption isotherms, and energy-dispersive X-ray spectroscopy. The XRD patterns of the pure and co-doped TiO₂ samples indicate that the predominant phase was anatase. The average grain size obtained from TEM was approximately 10 nm. The Brunauer–Emmett–Teller analysis results indicate that the specific surface area was 77.7 m² g^?1. The UV–Vis DRS results for the co-doped sample reveal an absorption edge that had been red-shifted to 500 nm. The photocatalytic activities of the samples were evaluated through photodegradation of papermaking wastewater under UV and visible light irradiation. Compared with the cobalt-doped TiO₂ sample and Degussa P25, the 3 mol% N-doped mesoporous N/Co-TiO₂ photocatalyst exhibited the highest photocatalytic activity, which can be ascribed to the synergistic effect of the N and Co co-doping.     

Photocatalytic activity of (sulfur,nitrogen)-codoped mesoporous TiO<Subscript>2</Subscript> thin films

Nitrogen and sulfur co-doped mesoporous TiO₂ thin films were fabricated using thiourea as a doping resource by the combination of the sol–gel and evaporation-induced self-assembly (EISA) processes. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N₂ adsorption–desorption, and UV–vis spectra were performed to characterize the as-synthesized mesoporous TiO₂ materials. The XPS result shows that O–Ti–N and O–Ti–S bonds in the (S, N)-codoped mesoporous TiO₂ were formed. The resultant mesoporous (S, N)-codoped TiO₂ exhibited anatase framework with a high porosity and a narrow pore distribution. After being illuminated for 3 h, methyl orange (MO) could be degraded completely by the co-doped sample under the ultraviolet irradiation, whereas mesoporous TiO₂ film without doping could only degrade 60% MO. After being illuminated by visible light, the water contact angles of the mesoporous co-doped TiO₂ samples decreased slightly, but the pure TiO₂ mesoporous film exhibited no change in the hydrophilicity.