Photocatalytic degradation of organic compounds diluted in water using visible light-responsive metal ion-implanted TiO2 catalysts: Fe ion-implanted TiO2

The application of metal ion-implantation method has been made to improve the electronic properties of the TiO₂ photocatalyst to realize the utilization of visible light. The photocatalytic properties of these unique TiO₂ photocatalysts for the purification of water have been investigated. By the metal ion-implantation method, metal ions (Fe⁺, Mn⁺, V⁺, etc.) are accelerated enough to have the high kinetic energy (150 keV) and can be implanted into the bulk of TiO₂. TiO₂ photocatalysts which can absorb visible light and work as a photocatalyst efficiently under visible light irradiation were successfully prepared using this advanced technique. The UV-Vis absorption spectra of these metal ion-implanted TiO₂ photocatalysts were found to shift toward visible light regions depending on the amount and the kind of metal ions implanted. They were found to exhibit an effective photocatalytic reactivity for the liquid-phase degradation of 2-propanol diluted in water at 295 K under visible light (λ>450 nm) irradiation. The investigation using XAFS analysis suggested that the substitution of Ti ions in TiO₂ lattice with implanted metal ions is important to modify TiO₂ to be able to adsorb visible light.     

Preparations and photocatalytic properties of magnetically separable nitrogen-doped TiO2 supported on nickel ferrite

A magnetically separable nitrogen-doped photocatalyst TiO_2−xN_x/SiO₂/NiFe₂O₄ (TSN) with a typical ferromagnetic hysteresis was prepared by a simple process: the magnetic SiO₂/NiFe₂O₄ (SN) dispersion prepared by a liquid catalytic phase transformation method and the visible-light-active photocatalyst TiO_2−xN_x were mixed, sonificated, dried, and calcined at 400 °C. The prepared photocatalyst is photoactive under visible light irradiation and easy to be separated from a slurry-type photoreactor under the application of an external magnetic field, being one of promising photocatalysts for wastewater treatment. Transmission electron microscope (TEM) and X-ray diffractometer (XRD) were used to characterize the structure of the TSN photocatalyst. The results indicate that the magnetic SiO₂/NiFe₂O₄ (SN) nanoparticles adhere to the surface of TiO_2−xN_x congeries. The magnetic photocatalyst TSN shows high catalytic activity for the degradation of methyl orange in water under UV and visible light irradiation (λ > 400 nm). SiO₂ coating round the surface of NiFe₂O₄ nanoparticles prevents effectively the injection of charges from TiO₂ particles to NiFe₂O₄, which gives rise to the increase in photocatalytic activity. Moreover, the recycled TSN exhibits a good repeatability of the photocatalytic activity.     

Low temperature preparation and visible light photocatalytic activity of mesoporous carbon-doped crystalline TiO2

A visible-light-active TiO₂ photocatalyst was prepared through carbon doping by using glucose as carbon source. Different from the previous carbon-doped TiO₂ prepared at high temperature, our preparation was performed by a hydrothermal method at temperature as low as 160 °C. The resulting photocatalyst was characterized by XRD, XPS, TEM, nitrogen adsorption, and UV–vis diffuse reflectance spectroscopy. The characterizations found that the photocatalyst possessed a homogeneous pore diameter about 8 nm and a high surface area of 126 m²/g. Comparing to undoped TiO₂, the carbon-doped TiO₂ showed obvious absorption in the 400–450 nm range with a red shift in the band gap transition. It was found that the resulting carbon-doped TiO₂ exhibits significantly higher photocatalytic activity than the undoped counterpart and Degussa P25 on the degradation of rhodamine B (RhB) in water under visible light irradiation (λ > 420 nm). This method can be easily scaled up for industrial production of visible-light driven photocatalyst for pollutants removal because of its convenience and energy-saving.     

银掺杂二氧化钛/活性炭复合材料的制备及其光催化性能研究

为提高二氧化钛/活性炭（AC）复合材料对可见光的利用率,基于溶胶-凝胶法制备了银掺杂的二氧化钛/活性炭复合光催化剂。利用一系列测试方法对光催化剂进行了表征,通过亚甲基蓝（MB）和Cr（Ⅵ）废水的降解效果研究了其光催化活性。结果表明,掺杂银的材料,吸附性能和可见光下的光催化性能均得到提升。在材料投加量为400 mg/L情况下,银-二氧化钛/AC复合光催化剂在30 min内对10 mg/L MB溶液的降解率达到98.55%,在60 min内对20 mg/L MB溶液、10 mg/L Cr（Ⅵ）溶液的降解率分别达到76.92%和53.90%;与未掺杂的材料相比,降解率分别提升了14%、47%、137%。这是由于Ag纳米颗粒可以有效地俘获价带电子,减少电子空穴的复合,从而提高了光催化效果。     

Visible light photocatalysis on praseodymium(III)-nitrate-modified TiO2 prepared by an ultrasound method

Nanocrystalline TiO₂ incorporated with praseodymium(III) nitrate has been prepared by an ultrasound method in a sol–gel process. The prepared sample is characterized by X-ray diffraction (XRD), nitrogen adsorption (BET surface area), UV–vis diffuse reflectance spectroscopy (UV–Vis DRS) and X-ray photoelectron spectroscopy (XPS). The prepared material consists of TiO₂ nanocrystalline with 5 nm size incorporated with highly dispersed Pr(NO₃)₃. Visible light absorptions at 444, 469, 482 and 590 nm are observed in the prepared sample. These bands are attributed to the 4f transitions ³H₄ → ³P₂, ³H₄ → ³P₁, ³H₄ → ³P₀ and ³H₄ → ¹D₂ of praseodymium(III) ions, respectively. This sample Pr(NO₃)₃-TiO₂, as a novel visible light photocatalyst, shows high activity and stability in the decomposing rhodamine-B (RhB) and 4-chlorophenol (4-CP) under visible light irradiation. Results examined by electron spin resonance spectroscopy (ESR) reveal that the irradiation (>420 nm) of the photocatalyst dispersed in RhB aqueous solution induces the generation of highly active hydroxyl radicals (OH), leading to the cleavage of the whole conjugated chromophore structure of RhB. A mechanism based on local excitation of praseodymium(III) nitrate chromophore and interfacial charge transfer from the chromophore to TiO₂ is proposed to explain the formation of active hydroxyl radicals in the photocatalytic system under visible light irradiation.     

The effect of the hydrothermal treatment with aqueous NaOH solution on the photocatalytic and photoelectrochemical properties of visible light-responsive TiO2 thin films

The effect of the hydrothermal treatment with aqueous NaOH solution on the photoelectrochemical and photocatalytic properties of visible light-responsive TiO₂ thin films prepared on Ti foil substrate (Vis-TiO₂/Ti) by a radio-frequency magnetron sputtering (RF-MS) deposition method has been investigated. The hydrothermally treated Vis-TiO₂/Ti electrodes exhibited a significant increase in their photocurrent under UV and visible light irradiation as compared to untreated Vis-TiO₂/Ti electrode. SEM investigations revealed that the surface morphology of Vis-TiO₂/Ti are drastically changed from the assembly of the TiO₂ crystallites to the stacking of nanowires with diameters of 30–50 nm with increasing hydrothermal treatment time (3–24 h), accompanying the increase in their surface area. The separate evolution of H₂ and O₂ from water under solar light irradiation was successfully achieved using the Vis-TiO₂/Ti/Pt which is hydrothermally treated for 5 h, while the H₂ evolution ratio was 15 μmol h⁻¹ in the early initial stage, corresponding to a solar energy conversion efficiency of 0.23%.     

硫化镉-二氧化钛/分子筛复合光催化材料制备及性能研究

将水热法制备的二氧化钛负载在分子筛上,再与硫化镉复合,制备了硫化镉-二氧化钛/分子筛复合材料。对复合材料的相组成、微观结构、形貌和光谱性质进行了表征。在可见光照射下,以光催化降解亚甲基蓝为探针反应,研究了复合材料的光催化活性。结果表明：与纯二氧化钛相比,二氧化钛/分子筛具有更快的吸附降解效率;与二氧化钛/分子筛、硫化镉/分子筛相比,硫化镉-二氧化钛/分子筛复合材料的光催化性能最为优越。硫化镉-二氧化钛/分子筛优化制备条件：硫化镉溶液质量浓度为2.0 g/L、反应温度为80 ℃,反应时间为4 h。     

Photocatalytic degradation of omethoate using NaY zeolite-supported TiO2

The degradation of omethoate was conducted using H₂O₂ as oxidant, TiO₂ supported on NaY zeolite as photocatalyst and a 300 W lamp as light source. The effect of the calcination temperature of the photocatalyst, the amount of TiO₂ loaded on NaY zeolite, the photocatalyst amount, the pH value and the radiation time on the degradation ratio of omethoate were investigated. The results show that TiO₂/NaY zeolite photocatalyst prepared by sol-gel method had good photocatalysis. The photocatalytic optimum oxidation conditions of omethoate are as follows: the calcination temperature of the photocatalyst is 550°C,the amount of TiO₂ loaded on NaY zeolite is 35.2 wt-%, the amount of photocatalyst is 5 g/L, pH=8 and the radiation time is 180 min. Under these conditions, the removal ratio of omethoate is up to 93%.     

Photocatalytic reduction of water by TaON under visible light irradiation

Some noble metals have been studied as H₂ evolution promoters for TaON, a visible light driven oxynitride photocatalyst. H₂ evolution on TaON photocatalyst under visible light irradiation (420 nm≤λ≤500 nm) in an aqueous methanol solution was found to be remarkably enhanced by adding Ru as a noble metal co-catalyst.     

铋基半导体复合二氧化钛光催化研究进展

光催化因绿色环保、可利用丰富的太阳能被广泛应用于环境污染治理和能源开发领域。二氧化钛作为典型的半导体光催化剂,因制备简易、价格低廉、对环境友好而一直备受关注。然而其较宽的禁带宽度、光生载流子易复合等缺点限制了其广泛应用,解决这些缺陷成为目前的主要工作。铋基半导体材料由于较为特殊的结构、带隙能较低、在可见光下有较高的光催化活性而近年来被关注。铋基半导体复合二氧化钛,能够突破二氧化钛固有的缺陷,从而进一步提高其复合体系的可见光光催化活性。介绍了二氧化钛的结构和催化原理,在此基础上着重综述了几种典型的铋基半导体复合二氧化钛纳米材料的制备方法、可见光催化原理以及应用。     

Preparation and performances of mesoporous TiO2 film photocatalyst supported on stainless steel

Mesoporous TiO₂ film photocatalysts supported on stainless steel substrates were prepared using the sol–gel method with Ti(OC₄H₉)₄ as a precursor and poly ethylene glycol (PEG) as a structure-directing agent. Mesoporous TiO₂ film with a pore diameter of about 15 nm was obtained with the addition of PEG (molecular WEIGHT =400). The pore diameter of TiO₂film was varied with molecular weight of PEG additive. The structure-directing process was also discussed. Mesoscopically ordered inorganic/polymer composites were believed to form during the process. Compared to conventional TiO₂ film photocatalyst, the mesoporous TiO₂ film showed a good performance for the photo degradation of rhodamine B (RB) solution irradiated with UV light of 365 nm. The photo degradation constant of rhodamine B for mesoporous TiO₂ film photocatalyst can arrive at 22 times of that for conventional TiO₂ film photocatalyst. Also an excellent performance for the degradation of gaseous formaldehyde with mesoporous film photocatalyst was obtained. The photo degradation rate of gaseous formaldehyde for mesoporous TiO₂ film photocatalyst can arrive at six times of that for conventional TiO₂ film photocatalyst.     

N-TiO2/g-C3N4复合光催化剂的制备及其光催化性能

采用水热法制备N掺杂TiO2,将其与二氰二胺混合进行高温焙烧合成N-TiO2/g-C3N4复合光催化剂。采用XRD、UV-Vis、N2吸附-脱附和SEM等对催化剂进行微观结构表征,以200W氙灯模拟光源并过滤掉420nm以下的紫外光,对比研究TiO2、g-C3N4、N-TiO2和复合光催化剂对罗丹明B的可见光降解性能。结果表明,N掺杂后TiO2的禁带宽度降低,催化活性提高;而复合光催化剂可见光吸收边距相对N-TiO2进一步红移,禁带宽度为2.75eV,降解罗丹明B的一级动力学常数k可达0.12158min-1,是g-C3N4、N-TiO2的2倍;复合催化剂重复使用4次后,对罗丹明B的降解率仍达92%以上,表明催化剂具有较好的光催化活性和稳定性。     

Effect of silver on the photocatalytic degradation of humic acid

In this study, humic acid was mineralized and degraded photocatalytically in presence of bare TiO₂ and silver loaded TiO₂ (0.5–5.0 at.% Ag). X-ray diffraction (XRD) and inductive coupled plasma (ICP) analysis confirm the complete photodeposition of silver over TiO₂ by photodeposition method. X-ray photoemission spectroscopy (XPS) studies confirmed the presence of Ag⁰ in all Ag–TiO₂ samples and the absence of Ag⁺ ions. Silver loading over TiO₂ improved the rate of mineralization and degradation of humic acid with a maximum loading of 1.0 at.% Ag. Ninety percent carbon from humic acid was mineralized to CO₂ only after 60 min by using bare TiO₂ as a photocatalyst. However, this conversion was possible within 40 min by using 1.0 at.% Ag-loaded TiO₂. This observation verifies that coating of metals like silver over TiO₂ acts as an electron sink and can improve the redox reaction by preventing electron–hole recombination reaction. The optimum 1.0 at.% Ag loading in the current work is indicative that the blocking of the TiO₂ surface active sites by silver also plays an important role in the photocatalytic mineralization and degradation of humic acid. As the silver loading is increased, less number of active site are available over the surface of photocatalyst TiO₂ for redox reaction. This finding was supported by the TEM analysis of the photocatalyst samples.     

光催化剂TiO2的改性研究进展

光催化剂TiO₂在环境污染治理领域呈现出广阔的应用前景,但由于其自身存在不能响应可见光和量子效率低的缺陷而限制了它的应用,改性是提高TiO₂光催化性能的重要手段。在总结国内外科研成果的基础上,综述了现阶段TiO₂的主要改性方法（如光敏化、离子掺杂、复合半导体等）研究进展,并对TiO₂改性方法的发展趋势进行了展望。     

Photocatalytic activity of TiO2/ZSM-5 composites in the presence of SO4 ion

TiO₂/ZSM-5 composites were prepared from SiO₂ of rice husk ash and TiO₂ sol from hydrolyzed TiOSO₄ salt. The combined effect of these two materials greatly enhanced the photocatalytic decolorization of methylene blue dye solution. The instant decolorization of the dye solution in the dark by the composite, TiO₂/ZSM-5 (wt ratio 1:1), resulted from the combination of the adsorption by ZSM-5 zeolite and TiO₂ nano-particles, and of Na₂SO₄ salt adhering to the composite surface. As a strong flocculating agent, the SO₄²⁻ ion caused the precipitation of the dye onto the composite surface which consequently enhanced the photocatalytic decolorization of the dye under UV irradiation. The composite, TiO₂/ZSM-5 (wt ratio 1:5), completely decolorized the methylene blue dye in 2.5 h, giving an equivalent performance to that of TiO₂, P-25 powder.     

可见光光催化剂的研究进展

综述TiO_2、改性TiO_2光催化剂和非TiO_2体系光催化剂在可见光催化领域的研究进展,概述了光催化剂的光催化原理和应用方向,针对可见光光催化剂发展现状中存在的量子效率和可见光利用率低、且回收难等问题进行阐述,并指出制备组成可控、形貌可控、易于回收利用且可见光利用率高的新型光催化剂是研究首要方向。     

Simulation of NO and NO2 sorption–desorption–reduction behaviours on Pt-impregnated HPW supported on TiO2

NO and NO₂ (NO_x) sorption, desorption and reduction by hydrogen, carbon monoxide and/or propene were investigated on a TiO₂-supported heteropolyacid, 12-tungstophosphoric acid hexahydrate (HPW), promoted by platinum. A model taking into account NO_x sorption, desorption and reduction was established. Kinetic constants for NO_x sorption, desorption and reduction were extracted by modelling for the investigated range of temperature (170–300 °C).     

Dye sensitized artificial photosynthesis in the gas phase over thin and thick TiO2 films under UV and visible light irradiation

Perylene diimide based organic sensitizers capable of electron generation under illumination were used to initiate gas phase photo reduction reactions on TiO₂ thin and thick film surfaces. For comparison [Ru(Bpy)₃]²⁺ dye sensitizers were also studied. The photo reduction of CO₂ was carried out under static conditions in the gas phase. TiO₂ films were coated on hollow glass beads via a sol–gel procedure. Pt was incorporated on the films either by adding the precursor salt in the sol, Pt(in), or by wet impregnation of calcined film with an aqueous solution of the precursor salt, Pt(on). Organic sensitizers were incorporated on the films by wet impregnation of the film from an aqueous solution. Under UV illumination, the methane yields of platinized TiO₂ thin films decreased in the following order: Pt(on)·TiO₂ > Pt(in)·TiO₂ > TiO₂. The presence of organic sensitizers inhibited the catalytic activity of pure and platinized TiO₂ thick films under UV illumination. The relative enhancement of the reaction yields in the presence of the organic sensitizer under visible light illumination depended on the presence of Pt as well as the incorporation method of Pt in the TiO₂ structure. The reaction yields were better when Pt was impregnated on the TiO₂ film than when Pt was incorporated in the Ti sol. On the other hand, pure or platinized TiO₂ under visible light illumination was totally inactive indicating the role of the organic dye in generating catalytically active electrons under visible light.     

氨基酞菁-二氧化钛可见-近红外光催化剂的制备及其性能

以可溶性氨基酞菁3,3',3",3"'-四(二甲氨基)铜酞菁(α-TDMACuPc)为敏化剂,采用溶胶-凝胶法制备了氨基酞菁-二氧化钛(α-TDMACuPc-TiO₂)光催化剂,通过紫外-可见吸收光谱(UV-Vis)、X射线衍射(XRD)对其进行了表征,并通过对甲基紫的光催化降解考察了α-TDMACuPc-TiO₂光催化剂的催化性能。结果表明,α-TDMACuPc在近红外光区有较强的吸收,敏化后的二氧化钛吸收可被拓展至可见-近红外光区,而且二氧化钛呈金红石晶型。α-TDMACuPc敏化后的二氧化钛在可见-近红外光区的催化活性明显提高,在α-TDMACuPc质量分数为1%时催化活性达到最高,而且光催化剂具有较好的稳定性。     

Characterization and photocatalytic activity of N-doped TiO2 prepared by thermal decomposition of Ti–melamine complex

Nitrogen doped spherical TiO₂ has been prepared by thermal decomposition of Ti–melamine complex in air atmosphere. A clear shift in the onset light absorption from UV region (<400) to visible region (>520 nm) has been observed for the N-doped samples. It has been deduced from the optical absorption spectra that the higher calcination temperature results in the decrease in the amount of N-doping. The XRD results revealed the phase transition of TiO₂ from anatase to rutile crystalline phase, starting at calcination temperature ≥600 °C. The electron microscopic images reveal the formation of spherical and flakes of TiO₂ nanocrystals (25 nm). The chemical nature of N in the N-TiO₂ has been evolved through X-ray photoelectron spectroscopy. The presence of different types of N species have been observed corresponding to different oxidation states and the presence of Ti–N and O–Ti–N have been confirmed from the observed binding energy values. Photocatalytic decomposition of methylene blue has been carried out both in the visible region and UV + visible region. In the visible region, N-TiO₂ showed higher activity compared to the undoped commercial TiO₂ (Degussa P25).