Fabrication of an efficient ternary TiO2/Bi2WO6 nanocomposite supported on g-C3N4 with enhanced visible-light- photocatalytic activity: Modeling and systematic optimization procedure

In this study, a ternary TiO₂/g-C₃N₄/Bi₂WO₆ nanocomposite was prepared via a facial approach. The final structure was applied as a new photocatalyst for the removal of brilliant green (BG) dye, as a model of organic pollutants, from the aqueous solution. The results of FESEM, EDS with mapping, XRD, FTIR, UV–vis DRS, PL, and EIS analyses further demonstrate the successful establishment of heterojunction between TiO_2, g-C₃N₄, and Bi₂WO₆. Integration of g-C₃N₄ and Bi₂WO₆ with TiO2 was remarkably decreased the band gap energy of TiO₂ to 2.68 eV (from 3.15 eV). The effects of various experimental factors such as TiO₂/g-C₃N₄/Bi₂WO₆ dosage, initial BG concentration, visible irradiation time, and pH on the photocatalyst behavior of TiO₂/g-C₃N₄/Bi₂WO₆ were investigated by 2 ^k-1 factorial design. The results of the analysis of variance demonstrate these experimental factors are effective on the BG degradation efficiency. The response surface methodology was applied to achieve the optimization procedure of BG degradation. According to these results, the complete BG removal efficiency was obtained for the optimal conditions of 15.76 mg of TiO₂/g-C₃N₄/Bi₂WO₆ nanocomposite, an initial BG concentration of 10 ppm, pH of 9, and time duration of 70 min. The improved photocatalytic performance of ternary TiO₂/g-C₃N₄/Bi₂WO₆ nanocomposite was related to the formation of heterojunction between TiO_2, g-C₃N₄, and Bi₂WO₆, significant light adsorption ability, and low recombination of photogenerated carriers.     

The effects of solvent on photocatalytic properties of Bi2WO6/TiO2 heterojunction under visible light irradiation

Bi₂WO₆/TiO₂ heterojunction photocatalysts with two different microstructures were controllably fabricated via a facile two-step synthetic route. XRD, XPS, SEM, TEM, BET-surface, DRS, PL spectra, photoelectrochemical measurement (Mott-Schottky), and zeta-potential analyzer were employed to clarify structural and morphological characteristics of the obtained products. The results showed that Bi₂WO₆ nanoparticles/nanosheets grew on the primary TiO₂ nanorods. The TiO₂ nanorods used as a synthetic template inhibit the growth of Bi₂WO₆ crystals along the c-axis, resulting in Bi₂WO₆/TiO₂ heterostructure with one-dimensional (1D) morphology. The photocatalytic properties of Bi₂WO₆/TiO₂ heterojunction photocatalysts were strongly dependent on their shapes and structures. Compared with bare Bi₂WO₆ and TiO₂, Bi₂WO₆/TiO₂ composite have stronger adsorption ability and better visible light photocatalytic activities towards organic dyes. The Bi₂WO₆/TiO₂ composite prepared in EG solvent with optimal Bi:Ti ratio of 2:12 (S-TB2) showed the highest photocatalytic activity, which could totally decompose Rhodamine B within 10 min upon irradiation with visible light (λ > 422 nm), and retained the high photocatalytic performance after five recycles, confirming its stability and practical usability. The results of PL indicated that Bi₂WO₆ and TiO₂ could combine well to form a heterojunction structure which facilitated electron–hole separation, and lead to the increasing photocatalytic activity.     

Core shell‐structured NiFe2O4@TiO2 nanoparticle‐anchored reduced graphene oxide for rapid degradation of rhodamine B

In this work, the NiFe₂O₄@TiO₂/reduced graphene oxide (RGO) ternary nanocomposites with high saturation magnetization and catalytic efficiency have been synthesized through the following steps. First, graphene oxide was prepared using the modified Hummer's method. Second, the NiFe₂O₄ nanoparticles were successfully prepared using the hydrothermal method. Third, the core shell‐structured NiFe₂O₄@TiO₂/RGO nanocomposite precursors were easily obtained through hydrolysis reaction. The morphology of NiFe₂O₄@TiO₂/RGO nanocomposites was characterized from scanning electron microscope (SEM) and transmission electron microscope (TEM) images. Moreover, the results of X‐ray diffraction (XRD) patterns proved that the TiO₂ coating shell consisted of anatase. The vibrating sample magnetometer (VSM) measurements showed that the saturation magnetization value of NiFe₂O₄@TiO₂/RGO ternary nanocomposites was 25 emu/g. The X‐ray photoelectron spectroscopy (XPS) analysis confirmed that only part of the graphite oxide (GO) was reduced to RGO in the ternary nanocomposite. The degradation experiments proved that NiFe₂O₄@TiO₂/RGO nanocomposite exhibited the high catalytic efficiency and outstanding recyclable performance for rhodamine B (RhB).     

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.     

有机改性TiO2光催化剂的制备及可见光催化性能

以染料黄叱精(Chrysoidine G)和TiO₂ (Degussa P25)为原料, 利用甲苯二异氰酸酯为桥连体, 成功合成了一种有机改性的TiO₂光催化剂. 采用XRD, TEM, FT-IR, UV-Vis对所得催化剂进行了表征, 以亚甲基蓝降解为探针反应, 考察其可见光催化性能. 结果表明: 甲苯二异氰酸酯在黄叱精和TiO₂之间形成了稳定的化学键, 从而实现了对TiO₂的表面有机改性; 改性后的TiO₂在可见光区(400～550 nm)有明显的吸收; 与未改性TiO₂相比, 有机改性的TiO₂催化剂在可见光照射下表现出了很好的光催化性能.     

Efficient Decomposition of Organic Pollutants Over In2O3/TiO2 Nanocomposite Photocatalyst Under Visible Light Irradiation

The heterojunction structures of In₂O₃/TiO₂, exhibiting visible light photocatalytic efficiency, has been synthesized by utilizing maleic acid as an organic linker to combine In₂O₃ and Degussa P25 (TiO₂) nanoparticles. The prepared nanocomposite has been characterized by FESEM, TEM, XRD and UV?CVisible reflectance spectra. The photocatalytic efficiency of the composite photocatalyst has been investigated based on the decomposition of 2-propanol (IP) in gas phase and 1,4-dichlorobenzene (DCB) in aqueous phase under visible light (??????420?nm) irradiation. The results reveal that the In₂O₃/TiO₂ composite photocatalyst with 7?wt% In₂O₃ demonstrated 6.3 times of efficiency in evolving CO₂ from gaseous IP and 8.7 times of efficiency in removing aqueous DCB in compare with Degussa P25. In this In₂O₃/TiO₂ composite system, TiO₂ seems to be the principal photocatalyst whereas the function of In₂O₃ is to sensitize TiO₂ by absorbing visible light (??????420?nm). The extraordinary high photocatalytic efficiency of this composite In₂O₃/TiO₂ under visible light has been explained on the basis of relative energy band positions of the component semiconductors.     

Green synthesis of activated carbon doped tungsten trioxide photocatalysts using leaf of basil (Ocimum basilicum) for photocatalytic degradation of methylene blue under sunlight

Tungsten oxide (WO₃) nanoparticles were prepared hydrothermally by basil leaves extract, and Activated Carbon (AC) was prepared by the carbonization of date pits. Moreover, 1, 2 and 3% of AC doped WO₃ nanoparticles have been fabricated under hydrothermal conditions. The obtained samples have been characterized by using different techniques such as x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), simultaneous thermogravimetric analysis (TG-DTGA), fourier transform infrared (FT-IR), BET surface area, and Ultra-Violet spectroscopy (UV–Vis). It was observed that band-gap energy of the fabricated materials decreases by increasing AC amount. Similarly, BET surface area and porosity results showed increasing the content of AC, surface area, pore size and pore volume were decreased. The functional groups, determined by FT-IR, played a significant role in the photocatalytic performance. The photocatalytic performance of fabricated samples was used for the degradation of methylene blue (MB) at neutral pH under visible light radiations, and it is observed that WO₃/3%AC photocatalyst showed the highest degradation of MB. Both, capped phytochemicals of basil extract and the nanocomposites, were improved the photocatalytic performance, about 94% photodegradation was observed within 25 min under the reaction conditions. The photocatalyst was stable and about 85% and 81% photodegradation of MB were found under the two times of reusability tests.     

Preparation of PANI-TiO2 nanocomposites and their solid-phase photocatalytic degradation

A series of polyaniline-anatase TiO₂ (PANI-TiO₂) nanocomposite powders with different PANI:TiO₂ ratios were prepared by ‘in-situ’ deposition oxidative polymerization of aniline hydrochloride using ammonium persulfate (APS) as oxidant in the presence of ultrafine grade powder of anatase TiO₂ cooled in an ice bath. And the solid-phase photocatalytic degradation of PANI-TiO₂ nanocomposites was investigated under the ambient air in order to assess the feasibility of developing photodegradable polymers. The photodegradation of the composite powders was compared with that of pure PANI powders by performing weight loss monitoring, elemental analysis, FT-IR and UV-vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The PANI-TiO₂ nanocomposite powders showed highly enhanced photodegradation and the photodegradation increased with decreasing ratios of PANI:TiO₂. A weight loss of about 6.8% was found for the PANI-TiO₂ (1:3) nanocomposite; however, the weight loss of the PANI-HCl powder was only 0.3% after being irradiated for 60 h under air. The photocatalytic degradation of the nanocomposite powders accompanied the peak intensity decrease in the FT-IR spectra at 1235 cm⁻¹, attributed to C-N stretching mode for benzenoid unit, and the depigmentation of the powders due to the visible light scattering from growing cavities. The elemental analysis and XPS analysis of the composite showed that the bulk and surface concentrations of N decreased with irradiation. A possible mechanism for the photocatalytical oxidative degradation was also mentioned.     

Preparation and measurement of properties of BiOBr/BiOCl/PANI ternary nanocomposite for highly efficient visible light photocatalytic applications

In this paper, we report the synthesis of the BiOBr/BiOCl/PANI ternary nanocomposite using a simple co-precipitation method. The modified photocatalyst produced was characterized by the FT-IR, FE-SEM equipped with EDS (as a Map), TEM, XRD, PL, Raman, and UV–Vis DRS analytical techniques. The synergetic effect of PANI and surface defects in nanoplates can prolong the recombination rate of photo-generated charge carriers. Thus, photocatalytic and photoelectrochemical activities of samples have been studied. Then, the methyl orange (MO) degradation performance of PANI/BiOBr and BiOBr/BiOCl/PANI was investigated under visible light irradiation. The lamp used to simulate sunlight in this photocatalytic study process was power down white light (5-W LED), less reported. The results got exhibited that the as-prepared BiOBr/BiOCl/PANI (90:10, Bi:PANI) nanocomposite showed a higher photocatalytic efficiency. Based on the scavenger tests, ^·O₂^? played a significant role in the degradation of MO. The connection between BiOBr, BiOCl, and PANI improved photocatalytic activity, which enhanced migration rate of the photo-generated electrons besides limiting the recombination of photo-generated electron–hole pairs.

     

Synthesis of Co3O4/WO3 Nanoheterojunction Photocatalyst for the Decomposition of Organic Pollutants Under Visible Light Irradiation

A highly efficient and visible light (λ ≥ 420 nm) responsive nanocomposite photocatalyst Co₃O₄/WO₃ was developed by dispersing p-type semiconductor Co₃O₄ on the surface of n-type semiconductor WO₃. The heterojunction Co₃O₄/WO₃ demonstrated higher photocatalytic activity than WO₃, Co₃O₄ and TiO₂ nanoparticles for the complete decomposition of 2-propanol in gas phase and phenol in aqueous phase and evolution of CO₂ under visible light irradiation. The highest photocatalytic efficiency of the composite Co₃O₄/WO₃ was observed when calcined at 300 °C for 2 h with 4.91 mol% Co₃O₄/WO₃. The enhanced photocatalytic efficiency of the heterojunction was discussed based on the unique relative energy band positions and profound absorption of visible light by the semiconductors.     

Preparation and characterization of rapid magnetic recyclable Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript>@TiO<Subscript>2</Subscript>–Sn photocatalyst

Effective procedure to synthesize Fe₃O₄@SiO₂@TiO₂–Sn magnetically separable photocatalyst by a combination of co-precipitation, sol–gel and photodeposition methods was introduced. Products were characterized by XRD, SEM, VSM, EDS, DRS, TEM, ICP-OES and IR techniques. The dimensions of catalyst particle size were evaluated by scanning electron microscopy, and results approved nanoscale size for product. In addition, studying the magnetic nature by VSM analysis showed superparamagnetic properties for all samples. XRD pattern indicates that TiO₂ coated on Fe₃O₄@SiO₂ core well crystallized at 400 °C in anatase phase. Synthesized photocatalyst shows good photocatalytic performance in decolorization of rhodamine B aqueous solution. The composite nanoparticles showed high recycling efficiency and stability over five separation cycles.     

稀土离子Tm3+掺杂Bi2WO6的可见光催化性能

以Na₂WO₄·2H₂O和Bi（NO₃）₃·5H₂O为主要原料,采用水热法合成了稀土离子Tm³⁺掺杂的Bi₂WO₆光催化剂。采用XRD、SEM、TEM、Raman、PL、DRS研究了Tm³⁺掺杂Bi₂WO₆的物相,微观形貌和可见光催化性能。结果表明,Tm³⁺掺杂有效提高了Bi₂WO₆的光催化性能,当掺杂量为6%时,样品的光催化性能最好,可见光照射30 min后,对罗丹明B的降解效率达到91.27%,而可见光照射5 h后,对焦糖色素的降解效率达45.25%。与未掺杂Bi₂WO₆相比,分别提高了27.78%和35.22%。     

具有分级多孔结构和光催化性质的核-壳纳米球(HP-Fe2O3@TiO2)

通过溶剂热和溶胶-凝胶涂层法, 设计并制备了具有分级多孔结构和光催化性质的核-壳纳米球(HP-Fe₂O₃@TiO₂). 透射电子显微镜(TEM)照片证明所得HP-Fe₂O₃@TiO₂样品具备分级多孔结构, 这是因为HP-Fe₂O₃@TiO₂的内核-Fe₂O₃具有大孔空隙, 同时外壳-TiO₂具有介孔空隙. 此外, 通过X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、X射线光电子能谱(XPS)以及氮气吸附-脱附曲线深入研究了HP-Fe₂O₃@TiO₂的结构及其性质. 分别在可见及紫外光照下, 研究了样品在H₂O₂体系下的光催化降解亚甲基蓝(MB)的性质. 所观察到的HP-Fe₂O₃@TiO₂纳米球的光催化性能, 可归因于核-壳结构的协同作用, 这进一步表明, TiO₂外壳对α-Fe₂O₃的光催化活性有重要影响作用. 在可见光照射下, HP-Fe₂O₃@TiO₂ (1 mL Ti(OC₄H₉)₄ (TBT))具有较优异的光催化活性. 同时, HP-Fe₂O₃@TiO₂ (4mL TBT)具备优异的单分散形貌, 并在紫外光照射下, 表现出最优的光催化活性.     

Preparation of a visible light-driven Bi2O3–TiO2 composite photocatalyst by an ethylene glycol-assisted sol–gel method,and its photocatalytic properties

A visible light-driven Bi₂O₃–TiO₂ composite photocatalyst was prepared by an ethylene glycol-assisted sol–gel method in which ethylene glycol acted as a polycondensation agent to capture metal ions by reacting with bismuth and titanium sources via a complex polycondensation pathway. The photocatalyst was characterized by X-ray photoelectron spectroscopy, X-ray diffraction, acquisition of N₂ adsorption–desorption isotherms, transmission electron microscopy, and UV–visible diffuse reflectance spectroscopy. The results revealed that the Bi₂O₃–TiO₂ composite was of smaller particle size, greater specific surface area, and had stronger absorbance in the visible light region than pure TiO₂. The photocatalytic activity of the as-prepared catalyst was evaluated by degradation of rhodamine B under visible light irradiation (λ > 400 nm); the as-prepared Bi₂O₃–TiO₂ composite was substantially more active than pure TiO₂. This was ascribed to the high surface area and the heterojunction structure.     

Synthesis of Three‐dimensionally Ordered Macroporous TiO2 and TiO2/WO3 Composites and Their Photocatalytic Performance

This work presents the characterization and preparation of three‐dimensionally ordered macroporous TiO₂ and TiO₂/WO₃ composite nanoparticles with enhanced visible‐light‐responsive properties for rhodamine B (Rh B) photodegradation. The 3DOM TiO₂ and TiO₂/WO₃ composites were prepared through a dip‐infiltrating sol‐gel process using a polystyrene (PS) colloidal crystal template. The materials were characterized by SEM, TEM, XRD, BET, XPS and UV/Vis. The 3DOM TiO₂/WO₃ composite structures ranged from well‐defined 3DOM structures, which are highly ordered and interconnected via small pore windows, to collapsed three‐dimensional structures as the WO₃ content increased. The photoresponse range and specific surface area of the composite increased with less than 0.025 g of WCl₆. The 3DOM TiO₂/WO₃ composite with less than 0.025 g of WCl₆ exhibited a higher catalytic activity than 3DOM TiO₂ for the photocatalytic degradation of Rh B under simulated sunlight illumination.     

稀土离子Tm3+掺杂Bi2WO6的可见光催化性能

以Na_2WO_4·2H_2O和Bi(NO_3)_3·5H_2O为主要原料,采用水热法合成了稀土离子Tm~(3+)掺杂的Bi_2WO_6光催化剂。采用XRD、SEM、TEM、Raman、PL、DRS研究了Tm~(3+)掺杂Bi_2WO_6的物相,微观形貌和可见光催化性能。结果表明,Tm~(3+)掺杂有效提高了Bi_2WO_6的光催化性能,当掺杂量为6%时,样品的光催化性能最好,可见光照射30 min后,对罗丹明B的降解效率达到91.27%,而可见光照射5 h后,对焦糖色素的降解效率达45.25%。与未掺杂Bi_2WO_6相比,分别提高了27.78%和35.22%。     

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。     

Visible-light-driven heterostructure Ag/Bi2WO6 nanocomposites synthesized by photodeposition method and used for photodegradation of rhodamine B dye

Visible-light-driven heterostructure Ag/Bi₂WO₆ nanocomposites were prepared by transforming Ag⁺ ions into metallic Ag⁰ nanoparticles loaded on top of Bi₂WO₆ nanoplates under visible light irradiation for 1 h. XRD, XPS, SEM and TEM analyses indicated that spherical metallic Ag nanoparticles were uniformly dispersed on top of orthorhombic Bi₂WO₆ thin nanoplates. Rhodamine B (RhB) was used as a dye model for investigation of photocatalytic performance of Bi₂WO₆ nanoplates with different weight contents of Ag nanoparticles illuminated by visible radiation. In this research, 10% Ag/Bi₂WO₆ nanocomposites have the highest photocatalytic activity in the degradation of RhB at 94.21% within 210 min because of the rapid diffusion of electronic charge through the Schottky barrier between metallic Ag nanoparticles and Bi₂WO₆ thin nanoplates, good electrical conductivity of metallic Ag nanoparticles, inhibited recombination of charge carriers and enhanced photocatalytic activity of Ag/Bi₂WO₆ nanocomposites. Main active species of the photocatalysis and stability of the photocatalyst were also evaluated.

     

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.     

Synthesis of Bi<Subscript>2</Subscript>O<Subscript>4</Subscript>@TiO<Subscript>2</Subscript> Heterojunction with Enhanced Visible Light Photocatalytic Activity

A novel Bi₂O₄@TiO₂ heterojunction was constructed by a simple two-step method. The charges migration between Bi₂O₄ and TiO₂ via the heterojunction improves the electron/hole separation efficiency. Furthermore, Bi₂O₄@TiO₂ heterostructures exhibit better adsorption capability for methyl orange molecular due to their higher specific surface area than pure Bi₂O₄. As a result, Bi₂O₄@TiO₂ hybrids show an improved visible light photocatalytic activity and photostability for the degradation of methyl orange.