Photodegradation of Rhodamine B on Sulfur Doped ZnO/TiO2 Nanocomposite Photocatalyst under Visible-light Irradiation

Sulfur doped ZnO/TiO₂ nanocomposite photocatalysts were synthesized by a facile sol‐gel method. The structure and properties of catalysts were characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), UV‐vis diffusive reflectance spectroscopy (DRS) and N₂ desorption‐adsorption isotherm. The XRD study showed that TiO₂ was anatase phase and there was no obvious difference in crystal composition of various S‐ZnO/TiO₂. The XPS study showed that the Zn element exists as ZnO and S atoms form SO^2?₄. The prepared samples had mesoporosity revealed by N₂ desorption‐adsorption isotherm result. The degradation of Rhodamine B dye under visible light irradiation was chosen as probe reaction to evaluate the photocatalytic activity of the ZnO/TiO₂ nanocomposite. The commercial TiO₂ photocatalyst (Degussa P25) was taken as standard photocatalyst to contrast the prepared different photocatalyst in current work. The improvement of the photocatalytic activity of S‐ZnO/TiO₂ composite photocatalyst can be attributed to the suitable energetic positions between ZnO and TiO₂, the acidity site caused by sulfur doping and the enlargement of the specific area. S‐3.0ZnO/TiO₂ exhibited the highest photocatalytic activity under visible light irradiation after Zn amount was optimized, which was 2.6 times higher than P25.     

Photocatalytic Hydrogen Evolution Coupled with Production of Highly Value-Added Organic Chemicals by a Composite Photocatalyst CdIn2S4@MIL-53-SO3Ni1/2

Photocatalytic water splitting coupled with the production of highly value-added organic chemicals is of significant importance, which represents a very promising pathway for transforming green solar energy into chemical energy. Herein, we report a composite photocatalyst CdIn₂S₄@MIL-53-SO₃Ni_1/2, which is highly efficient on prompting water splitting for the production of H₂ in the reduction half-reaction and selective oxidation of organic molecules for the production of highly value-added organic chemicals in the oxidation half-reaction under visible light irradiation. The superior photocatalytic properties of the composite photocatalyst CdIn₂S₄@MIL-53-SO₃Ni_1/2 should be ascribed to coating suspended ion catalyst (SIC), consisting of redox-active Ni^II ions in the anionic pores of coordination network MIL-53-SO₃⁻, on the surface of photoactive CdIn₂S₄, which endows photogenerated electron-hole pairs separate more efficiently for high rate production of H₂ and selective production of highly value-added organic products, demonstrating great potential for practical applications.     

An efficient Ag/MIL-100(Fe) catalyst for photothermal conversion of CO2 at ambient temperature

The conversion of CO₂ under mild condition is of great importance because these reactions involving CO₂ can not only produce value-added chemicals from abundant and inexpensive CO₂ feedstock but also close the carbon cycle. However, the chemical inertness of CO₂ requires the development of high-performance catalysts. Herein, Ag nanoparticles/MIL-100(Fe) composites were synthesized by simple impregnation-reduction method and employed as catalysts for the photothermal carboxylation of terminal alkynes with CO₂. MIL-100(Fe) could stabilize Ag nanoparticles and prevent them from aggregation during catalytic process. Taking the advantages of photothermal effects and catalytic activities of both Ag nanoparticles and MIL-100(Fe), various aromatic alkynes could be converted to corresponding carboxylic acid products (86%–92% yields) with 1 atm CO₂ at room temperature under visible light irradiation when using Ag nanoparticles/MIL-100(Fe) as photothermal catalysts. The catalysts also showed good recyclability with almost no loss of catalytic activity for three consecutive runs. More importantly, the catalytic performance of Ag nanoparticles/MIL-100(Fe) under visible light irradiation at room temperature was comparable to that upon heating, showing that the light source could replace conventional heating method to drive the reaction. This work provided a promising strategy of utilizing solar energy for achieving efficient CO₂ conversion to value-added chemicals under mild condition.     

Degradation products formed during UV exposure of polyethylene-ZnO nano-composites

Photodegradation of low density polyethylene (LDPE) containing nano-particulate ZnO has been studied using FTIR to follow the development of oxidation products in the polymer film and to monitor carbon dioxide evolved as a principal product of oxidation. The degradation behaviour of ZnO-free LDPE has been compared with that of compounds containing 0.25% and 0.75% ZnO and these results are compared with those obtained using similar films containing nano-particulate TiO₂. Under UV exposure, the presence of ZnO accelerated the development of carbonyl groups and CO₂ production. The carbonyl group development was more rapid when TiO₂ was used whereas ZnO caused greater CO₂ generation. Carbonyl group development seemed to correlate better with the reduction in mechanical properties whereas CO₂ generation correlated better with weight change measurements. The influence of ZnO on the oxidation pathways in LDPE is discussed; it is proposed that photo-oxidation is relatively much more likely to occur at terminal sites (rather than at pendent sites) when ZnO is present.     

Photodegradation of rhodamine B over semiconductor supported gold nanoparticles: The effect of semiconductor support identity

Rhodamine B (RB) is a toxic dye used extensively in textile industry, which must be remediated before its drainage to environment. In the present study, supported gold nanoparticles on commercially available titania and zincite were successfully prepared and then their activity on the photodegradation of RB under UV A light irradiation was evaluated. The synthesized photocatalysts were characterized by ICP, BET, XRD, TEM and EDX. Kinetic results showed that Au/TiO₂ was a photocatalyst inferior to Au/ZnO. This observation could be attributed to the strong reflection of UV irradiation by gold nanoparticles over TiO₂ support.     

Hydrothermal Preparation and Characterization of TiO2/BiVO4 Composite Catalyst and its Photolysis of Water to Produce Hydrogen

In the present work, bismuth vanadate composited photocatalysts were synthesized and characterized. X‐ray diffractometry and Raman results showed that the particles were well crystallized, and formed by the complex of monoclinic BiVO₄ and TiO₂. On electron microscopy, the photocatalyst exhibited high crystallization, agglutination and irregular shape, and was surrounded by numerous TiO₂ particles. The study of surface areas showed that the specific surface area of 30‐BiVO₄/TiO₂ composited was 112 m²·g^?1, which was nearly 10 times that of pure BiVO₄. The ultraviolet–visible diffuse reflectance spectra indicated the composited photocatalyst were activated in visible light. The activity of photocatalytic water splitting was studied. The results showed that monomer BiVO₄ photocatalyst was not able to produce hydrogen under any light source. BiVO₄/TiO₂ composited photocatalysts, however, were capable of generating hydrogen. Under UV light irradiation for 120 min, 1 g catalyst dispersed in 50 mL deionized water produced almost 1 mL hydrogen, such that the productivity of hydrogen was higher than that of P25‐TiO₂. Photocatalytic decomposition of water under visible light also confirmed that the BiVO₄/TiO₂ composited photocatalyst had the ability of water splitting.     

Photocatalytic Reduction of Nitro Compounds Using TiO2 Photocatalyst by UV and Vis Dye-sensitized Systems

Nitro‐aromatic compounds can be photocatalytically reduced into the corresponding amine‐aromatic compounds using TiO₂ as a photocatalyst in the UV/TiO₂/holes scavenger and Vis/TiO₂/dye‐sensitized systems. In the UV/TiO₂/holes scavenger system, reaction substrate alcohols such as methanol could be used as the holes scavengers, and in the Vis/TiO₂/dye‐sensitized system, substrate alcohols could be oxidized to the corresponding aldehydes with high selectivity. When methanol was used as the holes scavengers and the illumination time was 6 h, 87.2% of p‐nitrotoluene could be photocatalytically reduced into p‐toluidine. In the Vis/TiO₂/dye‐sensitized system, the effect of aromatic alcohols for the photocatalytic reduction of nitrobenzene was better than that of other alcohols. At the same time, aromatic alcohols can be easily oxidized, and the production efficiencies of the corresponding aldehydes were higher than those of other alcohols. The possible reaction mechanisms were also proposed.     

CdS‐Encapsulated TiO2 Nanotube Arrays Lidded with ZnO Nanorod Layers and Their Photoelectrocatalytic Applications

A novel TiO₂ nanotube array/CdS nanoparticle/ZnO nanorod (TiO₂ NT/CdS/ZnO NR) photocatalyst was constructed which exhibited a wide‐absorption (200–535 nm) response in the UV/Vis region and was applied for the photoelectrocatalytic (PEC) degradation of dye wastewater. This was achieved by chemically assembling CdS into the TiO₂ NTs and then constructing a ZnO NR layer on the TiO₂ NT/CdS surface. Scanning electron microscopy (SEM) results showed that a new structure had been obtained. The TiO₂ NTs looked like many “empty bottles” and the ZnO NR layer served as a big lid. Meanwhile the CdS NPs were encapsulated between them with good protection. After being sensitized by the CdS NPs, the absorption‐band edge of the obtained photocatalyst was obviously red‐shifted to the visible region, and the band gap was reduced from its original 3.20 eV to 2.32 eV. Photoelectric‐property tests indicated that the TiO₂ NT/CdS/ZnO NR material maintained a very high PEC activity in both the ultraviolet (UV) and the visible region. The maximum photoelectric conversion efficiencies of TiO₂ NT/CdS/ZnO NR were 31.8 and 5.98 % under UV light (365 nm) and visible light (420–800 nm), respectively. In the PEC oxidation, TiO₂ NT/CdS/ZnO NR exhibited a higher removal ability for methyl orange (MO) and a high stability. The kinetic constants were 1.77×10^?4 s^?1 under UV light, which was almost 5.9 and 2.6 times of those on pure TiO₂ NTs and TiO₂ NT/ZnO NR, and 2.5×10^?4 s^?1 under visible light, 2.4 times those on TiO₂ NT/CdS.     

Cu2O/reduced graphene oxide/TiO2 nanomaterial: An effective photocatalyst for azide-alkyne cycloaddition with benzyl halides or epoxide derivatives under visible light irradiation

Cu₂O/reduced graphene oxide/TiO₂ (Cu₂O/rGO/TiO₂) photocatalyst was synthesized under ultrasonic irradiation. The nanomaterial was identified by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, UV–vis absorption, and inductively coupled plasma optical emission spectroscopy (ICP-OES). The Cu₂O/rGO/TiO₂ photocatalyst was utilized in “click” reaction for the preparation of 1,4-disubstituted 1,2,3-triazoles via one pot multicomponent reaction of benzyl halide or epoxide derivatives with alkynes in presence of NaN₃ and triethylamine under visible light irradiation. The “click” reaction was performed under mild conditions affording good to excellent yields of the triazole compounds using low catalyst loading in short reaction times. The nanocomposite was recovered and recycled for five successive runs without a major diminution in its catalytic performance.     

Efficient and Robust Cu/TiO2 Nanorod Photocatalysts for Simultaneous Removal of Cr(VI) and Methylene Blue under Solar Light

Because of its large bandgap, TiO₂ can function only under UV light. TiO₂ surface modification with noble metal nanoparticles can extend the light absorption from UV to visible light region and enhance the photocatalytic quantum yield. In this work, TiO₂ nanorods (Cu/TiO₂) modified by copper nanoparticles were prepared by a one‐step solvothermal method at low cost. The resultant Cu/TiO₂ nanorods show excellent synergistic effect in the oxidation of methylene blue (MB) and the reduction of aqueous Cr(VI) under solar light irradiation. Mechanistic investigation suggests that the Cr(VI) species could effectively scavenge the electrons from MB in the presence of the as‐prepared photocatalyst, leading to the simultaneous removal of both pollutants. Being economically viable, environmentally sustainable, and highly efficient, the proposed photocatalyst holds promise for technologies involving simultaneous organic degradation and heavy metal removal in wastewater treatment.     

Synthesis,characterization and photocatalytic application of TiO2/magnetic graphene for efficient photodegradation of crystal violet

A magnetized nano‐photocatalyst based on TiO₂/magnetic graphene was developed for efficient photodegradation of crystal violet (CV). Scanning electron microscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy and elemental mapping were used to characterize the prepared magnetic nano‐photocatalyst. The photocatalytic activity of the synthesized magnetic nano‐photocatalyst was evaluated using the decomposition of CV as a model organic pollutant under UV light irradiation. The obtained results showed that TiO₂/magnetic graphene exhibited much higher photocatalytic performance than bare TiO₂. Incorporation of graphene enhanced the activity of the prepared magnetic nano‐photocatalyst. TiO₂/magnetic graphene can be easily separated from an aqueous solution by applying an external magnetic field. Effects of pH, magnetized nano‐photocatalyst dosage, UV light irradiation time, H₂O₂ amount and initial concentration of dye on the photodegradation efficiency were evaluated and optimized. Efficient photodegradation (>98%) of the selected dye under optimized conditions using the synthesized nano‐photocatalyst under UV light irradiation was achieved in 25 min. The prepared magnetic nano‐photocatalyst can be used in a wide pH range (4–10) for degradation of CV. The effects of scavengers, namely methanol (OH^? scavenger), p‐benzoquinone (O₂^?? scavenger) and disodium ethylenediaminetetraacetate (hole scavenger), on CV photodegradation were investigated.     

Fe3+掺杂TiO2/凹凸棒复合光催化剂的制备和光催化活性

用酸催化溶胶-凝胶法制备了Fe³⁺掺杂TiO₂/凹凸棒（Fe³⁺-TiO₂/ATP）复合光催化剂,对其结构、微观形貌、光吸收性能和可见光下的光催化性能进行了表征。XRD和TEM测试结果表明,Fe³⁺-TiO₂/ATP具有较好的热稳定性,经450 ℃热处理后的ATP晶体结构基本保持不变,锐钛矿TiO2均匀的分布在ATP表面,TiO2颗粒之间无团聚,且平均粒径小于纯TiO₂。UV-Vis-DRS测试结果表明,Fe³⁺的掺杂可明显增强复合光催化剂对可见光的吸收,光响应范围拓展到了整个紫外-可见光区。在可见光下,Fe³⁺-TiO₂/ATP复合光催化剂对亚甲基蓝具有很好的催化降解活性。Fe³⁺-TiO₂/ATP的反应速率常数分别为TiO₂/ATP、P25和纯TiO2的1.37、4.83和6.51倍。复合光催化剂的沉降性能优于纯TiO2和P25,易于分离。     

Synthesis and characterization of radiation sensitive TiO<Subscript>2</Subscript>/monazite photocatalyst

A TiO₂/monazite photocatalyst was prepared by embedding TiO₂ nanoparticles into a monazite substrate surface. TiCl₄ hydrolysis/citric acid chelating procedure under acidic conditions were used to synthesize the nanophase TiO₂ particles. The anatase TiO₂/monazite photocatalyst surface area, morphology, crystalline and elemental concentrations were characterized using Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), X-ray diffraction (XRD), and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Monazite contains a large amount of Ce-, La-, Nd- and Th-PO₄ compounds; it has been known as a natural mineral material with minor radioactivity. TiO₂-CeO₂ composite is a kind of radiation sensitive photocatalyst in which the radiations of thorium nuclides give energy to trigger TiO₂ and cerium ions which play an energy absorber with charge separator. The result showed that methylene blue and phenol were spontaneously photocatalytic decomposed by TiO₂/monazite composite even in a dark environment. A synergistic effect was also examined with applied exterior UV or ⁶⁰Co irradiation. A hybrid mechanism is proposed; according by the radioluminescence (RL) from excited Ce ion by γ-radiation soliciting CeO₂/TiO₂ heterojunction (HJ). This seems to be a possible mechanism to explain this self-activated photo-catalytic behavior.     

Photodegradation of dye pollutants on one-dimensional TiO2 nanoparticles under UV and visible irradiation

Titanium dioxides (TiO₂) nanoparticles with one-dimensional (1D) geometry, nanorods and nanostripes, were used as photocatalysts to photodegrade Rhodamine B (RhB) under ultraviolet (UV) and visible irradiation. The nanorods catalyst exhibited very interesting photocatalytic properties: under the UV irradiation its catalytic activity was slightly below that of the well-known TiO₂ catalyst P25, while under visible light it exhibited a better activity than P25.This fact indicates that the nanorods have a superior ability to utilize less energetic but more abundant visible light. Moreover, the 1D TiO₂ nanoparticles can be readily separated from aqueous suspensions by sedimentation after the reaction. With these advantages the 1D TiO₂ catalysts have a great potential for environmental applications. Various analytical techniques were employed to characterize TiO₂ catalysts and monitor the photocatalytic reaction. It was found that the catalytic performance of the catalysts is greatly dependent on their structures: The superior activity of P25 (consists of anatase and rutile nanocrystals) under UV light results probably from the interfacial interaction between anatase and rutile nanocrystals in this solid, which do not exist in the nanorods (only anatase). The titanate nanostripes (titanate) can absorb UV photons with shorter wavelength only.     

Photocatalytic Reduction of Greenhouse Gas CO2 to Fuel

Sun is the Earth’s ultimate and inexhaustible energy source. One of the best routes to remedy the CO₂ problem is to convert it to valuable hydrocarbons using solar energy. In this study, CO₂ was photocatalytically reduced to produce methanol, methane and ethylene in a steady-state optical-fiber reactor under artificial light and real sunlight irradiation. The photocatalyst was dip-coated on the optical fibers that enable the light to transmit and spread uniformly inside the reactor. The optical-fiber photoreactor, comprised of nearly 120 photocatalyst-coated fibers, was designed and assembled. The XRD spectra indicated the anatase phase for all photocatalysts. It is found that the methanol yield increased with UV light intensity. A maximum methanol yield of 4.12 μmole/g-cat h is obtained when 1.0 wt% Ag/TiO₂ photocatalyst was used under a light intensity of 10 W/cm². When mixed oxide, TiO₂–SiO₂, is doped with Cu and Fe metals, the resulting photocatalysts show substantial difference in hydrocarbon production as well as product selectivity. Methane and ethylene were produced on Cu–Fe loaded TiO₂–SiO₂ photocatalyst. Since dye-sensitized Cu–Fe/P25 photocatalyst can fully harvest the light energy of 400–800 nm from sunlight, its photoactivity was significantly enhanced. Finally, CO₂ photoreduction was studied by in situ IR spectroscopy and possible mechanism for the photoreaction was proposed.     

紫外和可见光照射下Fe-TiO2复合材料催化低浓度芳香族有机污染物降解（英文）

Fe‐TiO2 photocatalysts with different ratios of Fe to Ti were prepared by a sol‐gel process using tetra‐n‐butyl titanium and iron(III) nitrate as Ti and Fe sources, respectively. The photocatalytic function of the prepared composites was examined for the decomposition of low‐concentration(0.1 ppm) airborne benzene, toluene, ethyl benzene, and o‐xylene(BTEX). The Fe‐TiO2 composites were characterized by energy dispersive X‐ray spectroscopy, X‐ray diffraction, UV‐visible spectroscopy, and Fourier transform infrared spectroscopy. The time‐series ratios of outlet to inlet concentrations of toluene, ethyl benzene, and o‐xylene target chemicals, as determined by the Fe‐TiO2 composites under visible light exposure, were lower than or similar to those of the reference TiO2 photocatalyst. Moreover, the time‐series ratios of outlet to inlet concentrations of the three compounds, as determined for the Fe‐TiO2 composites, increased as the ratio of Fe to Ti increased from 0.001 to 0.010. In contrast, under UV exposure, the time‐series ratios of outlet to inlet concentrations of BTEX, determined for the Fe‐TiO2 composites, were similar to or higher than those obtained from the reference TiO2 photocatalyst. Fe‐TiO2 composites with an optimal Fe to Ti ratio could effectively be applied for the purification of low‐concentration aromatic organic pollutants.     

Sol-gel preparation of Fe-doped mixed crystal TiO<Subscript>2</Subscript> powder and its photocatalytic activity for degradation of azo fuchsine under visible light irradiation

In this work, the Fe-doped mixed crystal TiO₂ photocatalyst which can utilize visible light was prepared by sol-gel and heat-treated methods. During heat-treatment, the phase transformation of Fe-doped TiO₂ powder occurs and the process is characterized by XRD and TG-DTA technologies. Otherwise, the sizes and shapes of Fe-doped and undoped TiO₂ powders were also compared using TEM images. The azo fuchsine in aqueous solutions, as a model compound, was treated under visible light irradiation using Fe-doped mixed crystal TiO₂ powders as photocatalyst. The results showed that, under visible light irradiation, the (0.25%) Fe-doped mixed crystal TiO₂ powder heat-treated at 600°C for 3.0 h behaved very high photocatalytic activities for degradation of azo fuchsine. The remarkable improvement of the photocatalytic activity of TiO₂ powder was elucidated through the cooperative effects of iron doping and phase transformation. The iron doping can restrain the recombination of photogenerated electron-hole pairs and the phase transformation can enhance the absorption of visible light. Furthermore, other influence factors such as azo fuchsine concentration, solution acidity, Fe3+ ion content and irradiation time were also studied. Thus, this method is applicable for the treatment of wastewater.     

Kinetics and efficiency displayed by supported and suspended TiO2 catalysts applied to the disinfection of Escherichia coli

TiO₂-mediated photocatalysis is widely used in a variety of applications and products in the environmental and energy fields, including photoelectrochemical conversion, self-cleaning surfaces, and especially water purification systems. The dimensionality of the structure of a TiO₂ material can affect its properties, functions, and more specifically, its photocatalytic performance. In this work, the photocatalytic inactivation of Gram-negative Escherichia coli using three photocatalysts, differing in their structure and other characteristics, was studied in a batch reactor under UVA light. The aim was to establish the disinfection efficiency of solid TiO₂ compared with that of suspended catalysts, widely considered as reference cases for photocatalytic water disinfection. The bacterial inactivation profiles obtained showed that: (1) the photoinactivation was exclusively related to the quantity of photons retained per unit of treated volume, irrespective of the characteristics of the photocatalyst and the emitted light flux densities; (2) across the whole UV light range studied, each of the photocatalytic solids was able to achieve more than 2 log bacterial inactivation with less than 2 h UV irradiation; (3) none of the used catalysts achieved a total bacterial disinfection during the treatment time. For each of the catalysts the quantum yield has been assessed in terms of disinfection efficiency, the 2D material showed almost the same performance as those of suspended catalysts. This catalyst is promising for supported photocatalysis applications.     

TiO2 Nanopowder Catalyzed Microwave-Induced One-Pot Synthesis of Novel Quinoline/Benzo[h]quinoline3-carbonitrile Under Solvent Free Conditions

A rapid and efficient method for the synthesis of various carbonitrile quinoline/benzo[h]quinolines has been developed through the Knoevenagel condensation, Michael addition of aromatic aldehyde/amine with carbonyl compounds in the presence of a nanostructured TiO₂ photocatalyst by microwave irradiation under solvent-free conditions.     

CdS/TiO2纳米管复合结构的制备与光电性能研究

利用阳极氧化法在钛金属基底表面制备一层TiO2纳米管阵列薄膜,然后通过水热反应在TiO2纳米管上负载CdS纳米粒子,形成CdS/TiO2纳米管的复合结构。利用SEM、XRD、XPS、UV-Vis等手段对其形貌和结构进行表征。进一步考察了CdS/TiO2纳米管的光电性能和光催化活性,结果表明,相比于TiO2纳米管,CdS/TiO2纳米管复合结构在紫外光和可见光下都具有更好的光催化活性及光电性能。