One-dimensional spindle-like BiVO4/TiO2 nanofibers heterojunction nanocomposites with enhanced visible light photocatalytic activity

One-dimensional spindle-like BiVO₄/TiO₂ nanofibers heterojunction nanocomposites with high visible light photocatalytic activity have been successfully obtained by combining the electrospinning technique and solvothermal method. The as-obtained products were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis spectra and photoluminescence (PL) spectra. The results revealed that spindle-like BiVO₄ nanostructures were successfully grown on TiO₂ nanofibers. Photocatalytic tests showed that the BiVO₄/TiO₂ nanofibers heterojunction nanocomposites showed enhanced visible light photocatalytic activity than that of pure TiO₂ nanofibers, which might be attributed to the effective photogenerated electrons-holes separation based on the photosynergistic effect of the BiVO₄/TiO₂ heterojunction. Moreover, the BiVO₄/TiO₂ nanofibers heterojunction nanocomposites could be easily recycled without any decrease of the photocatalytic activity.     

TiO2/BiVO4复合光催化剂的微波辅助水热法合成及催化性能研究

以硝酸铋和偏钒酸铵为原料,采用微波-辅助水热法合成了BiVO4和TiO2/BiVO4复合光催化剂,借助XRD、UV-Vis和FE-SEM等测试手段对样品进行表征。XRD分析表明,所得BiVO4粉体为单斜晶系,且与TiO2复合后,特征衍射峰宽化,强度降低;FE-SEM显示,所得样品为具有多级结构的球状纳米结构体系;UV-Vis吸收光谱表明,BiVO4粉体和TiO2/BiVO4在400～600 nm的可见光区域对光响应。根据光吸收特性,选择罗丹明B为模型污染物,考察了样品可见光催化活性。结果表明,TiO2/BiVO4相比BiVO4,具有更高的可见光催化活性。     

BiVO_4/BiOCl复合材料的制备及其光催化性能的研究

通过水热-溶剂热法制备了BiVO4/BiOCl复合材料。采用X射线衍射、扫描电子显微镜、紫外-可见漫反射等测试手段对复合光催化剂的结构、形貌和光学性质进行表征。考察了其对罗丹明B的吸附性能和光催化性能。结果表明,与纯BiVO4样品相比,BiVO4/BiOCl样品对罗丹明B的吸附能力和光催化降解能力都显著增强。BiVO4/BiOCl对罗丹明B的光催化反应符合一级反应的特点,且复合光催化剂具有较高的稳定性,重复使用3次后,罗丹明B的降解率变化不明显,仍可达到95%。     

Preparation of calcined hydrotalcite/TiO2-Ag composite and enhanced photocatalytic properties

A series of calcined hydrotalcite/TiO₂-Ag (HTC/TiO₂-Ag) composites with different silver (Ag) contents were successfully prepared and investigated as a catalyst for the photodegradation of phenol using UV–vis light (λ>300 nm). The Ag nanoparticles were deposited on the surface of TiO₂ (TiO₂-Ag) through photodeposition method. The TiO₂-Ag nanoparticles were supported on hydrotalcite (HT) by the co-precipitation method at variable pH (HT/TiO₂-Ag), and then calcined at 500 °C to obtain the HTC/TiO₂-Ag composites. The composites were characterized by inductively coupled plasma mass spectrometry (ICP-MS), N₂ adsorption/desorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance spectra (DRS). Results show that there is an optimum silver ratio to obtain the highest photocatalytic performance in the HTC/TiO₂-Ag photocatalyst which is 2 wt%, and is assigned as HTC/TiO₂-Ag(2). The association of silver nanoparticles on TiO₂ enhanced photocatalytic activity of the bare semiconductor composite. Only 56% of phenol was photodegraded when photodegradation was performed with HTC/TiO₂, whereas ~100% was photodegraded using HTC/TiO₂-Ag(2). The data gathered from the photocatalytic degradation of phenol were successfully fitted to Langmuir-Hinshelwood model, and can be described by pseudo-first order kinetics. The results showed the HTC/TiO₂-Ag(2) as efficient photocatalyst, low cost, separable from solution by sedimentation, and reusable. The superior performance of HTC/TiO₂-Ag(2) composite photocatalyst may be attributed to the synergic catalytic effect between silver and TiO₂, dispersion of TiO₂-Ag(2) nanoparticles supported on calcined hydrotalcite, and the calcined hydrotalcite like photocatalyst.     

g-C_3N_4/BiVO_4复合光催化剂的制备与光催化性能研究

通过原位复合的方法制备不同配比的g-C3N4/BiVO4复合光催化剂,利用傅里叶红外光谱(FTIR)、X-射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见光漫反射光谱(UV-Vis DRS)和N2吸附-脱附对所制备的材料进行表征。并通过光催化降解有机染料罗丹明B对其光催化活性进行测试。结果表明,部分g-C3N4附着在BiVO4表面,g-C3N4/BiVO4复合光催化剂比纯的BiVO4光催化效果要好,并且确定了最佳复合比例,同时对复合光催化剂性能提高的机理进行了讨论。     

水热法制备Eu复合BiVO4纳米片及其光催化降解性能

水热法制备了以聚乙二醇(PEG-200)为模板剂的稀土元素Eu复合BiVO₄光催化剂,并对材料进行XRD、SEM、UV-vis DRS、BET的表征和分析.以光催化降解甲基蓝(MB)效率作为光催化活性的指标,考察Eu复合对BiVO₄光催化活性的影响.结果表明:Eu复合可使BiVO₄的晶型发生转变,同时又抑制四方相晶体生长,使晶粒尺寸变小,比表面积增大.复合样品中,部分Eu³⁺进入BiVO₄晶格内取代Bi³⁺,使晶形发生畸变,有利于光催化活性的提高.当Eu的复合量为50%时,光催化降解甲基蓝的效率最高,可见光照射120min降解效率可达到90%,较纯BiVO₄的光降解效率明显提高.     

Microwave hydrothermal synthesis of Sr doped ZnO crystallites with enhanced photocatalytic properties

Pure and Sr²⁺ doped ZnO crystallites were successfully synthesized via a microwave hydrothermal method using Zn(NO₃)₂·6H₂O and Sr(NO₃)₂·6H₂O as source materials. The phase and microstructure of the as-prepared Zn_1−xSr_xO crystallites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Ultraviolet–visible spectrum (UV–vis) and photochemical reaction instrument were used to analyze the photocatalytic properties of the particles. XRD results show that the diffraction peaks of the as-prepared Zn_1−xSr_xO crystallites shifted slightly toward lower 2θ angle with the increasing of Sr²⁺ doping concentration from 0% to 0.3%. The pure ZnO crystallites with lamellar structure are found transforming to a hexagonal columnar morphology with the increase of Sr²⁺ doping concentration. UV–vis analysis shows that the particles have a higher absorption in UV region with a slightly decreased of optical band (E_g) gap. The photocatalytic activity of Sr²⁺ doped ZnO crystallites was evaluated by the Rhodamine B (RhB) degradation in aqueous solution under visible-light irradiation. Compared with the pure ZnO particles, the photocatalytic properties of the Sr²⁺ doped ZnO crystallites are obviously improved. The photocatalysis experiment results demonstrate that the 0.1% Sr²⁺ doped ZnO exhibits the best photocatalytic activity for the degradation of Rhodamine B.     

Manifestation of enhanced and durable photocatalytic H2 production using hierarchically structured Pt@Co3O4/TiO2 ternary nanocomposite

A hierarchical structure composed of Pt@Co₃O₄/TiO₂ (CTP) ternary nanocomposite was synthesized and demonstrated for its enhanced and durable production of hydrogen from glycerol under simulated solar light irradiation. The rate of hydrogen production over the optimized composition was found to be 19.2 mmol h^?1 g^?1_cat. The obtained XRD and XPS results revealed the facile formation of the composite. The heterojunction formed in the ternary system remarkably enhanced the visible light absorption properties and charge separation in CTP as evidenced from their UV–visible absorption and PL spectra, respectively. The optimized union of the materials with specific properties and their intimate physical contacts might be the origin for the manifested, improved and durable photocatalytic efficiency towards hydrogen production.     

Eu掺杂BiVO4微纳米材料的制备及其光催化性能

采用一步水热法制备了Eu/BiVO4微纳米材料。通过X射线粉末衍射（XRD）、扫描电镜（SEM）、能谱微区分析（EDS）、X射线能谱（XPS）、紫外-可见漫反射吸收光谱（UV-Vis DRS）及光致发光光谱（PL）等手段对所制备的材料进行结构表征,并以罗丹明B为目标污染物研究了样品的光催化活性。考察了主要制备条件对样品晶相结构的影响。结果表明：在Bi3+与V5+的物质的量比为1∶1、前驱液pH=4、水热温度为160 ℃、水热时间为20 h、Eu的掺杂量为5%（物质的量分数）的条件下制备的Eu/BiVO4样品具有单斜白钨矿结构;该样品拥有优良的光催化性能,在可见光（200 W钨灯）照射1 h及H2O2助剂的存在下,对10 mg/L罗丹明B溶液的光降解率可达89.2%,比纯的BiVO4的光降解率提高了约30%。     

Ultrasound assisted synthesis of heterostructured TiO2/ZnFe2O4 and TiO2/ZnFe1.98La0.02O4 systems as tunable photocatalysts for efficient organic pollutants removal

As a response to the everyday growing concern about wastewater treatment, some new mesoporous TiO₂/ZnFe₂O₄ and TiO₂/ZnFe_1.98La_0.02O₄ catalysts were synthesized during this research. The ultrasound template-assisted sol-gel method was employed in the synthesis, using conventional calcination and microwave treatment for pore directing agent removal. The as-prepared samples were characterized from the structural, optical, morphological and textural points of view, confirming the presence of spinel ferrites and TiO₂ anatase crystals in the nanocomposites. The synthetized powders exhibit promising characteristics for their use in adsorption and light activated degradation of organic pollutants. The photodegradation experiments of model pollutant basic blue 9 (methylene blue) dye were performed at laboratory scale and the optimum experimental parameters were determined as 0.4 g/L catalyst and 30 mg/L initial dye concentration, under UV light irradiation, visible irradiation and natural sun light irradiation. The conventionally calcined lanthanum doped TiO₂/ZnFe_1.98La_0.02O₄ system exhibited the highest efficiencies of 97%, 70% and 91% for dye removal from the solution, under UV light, visible light and natural sun light irradiation, respectively. Moreover, the catalytic activity was similar for up to four consecutive cycles. A lower yield of organic pollutant removal was observed in wastewater treatment plant (WWTP) effluent. The obtained results show that the newly synthesized catalysts are good candidates for the removal of water pollutants through adsorption and photocatalysis.     

利用Sol-Gel法与水热合成法制备纳米TiO2及其光催化活性研究

以Sol-Gel法及水热合成方法制备了纳米TiO2,利用XRD进行了表征,以太阳光为光源,通过对亚甲基蓝溶液的降解反应,考察了两种方法所得样品的光催化活性。结果表明,利用水热合成法制备的锐钛矿型TiO2具有更小的粒径,而通过溶胶-凝胶制得的样品为混晶型TiO2,对亚甲基蓝降解具有较高的光催化活性。     

二氧化钛的沉积-沉淀水热制备及其光催化性能

以硫酸钛为原料,采用沉积-沉淀水热法制得了TiO2粉体光催化剂。以光催化降解活性艳红X-3B作为模型反应,考察了所制得的TiO2粉体的光催化性能。发现140℃沉积-沉淀水热反应20 h、600℃焙烧制得的TiO2粉体光催化活性明显高于Degussa P25 TiO2,并且该TiO2粉体光催化剂沉降性好,易分离。     

Fabrication of g-C3N4/TiO2 heterojunction composite for enhanced photocatalytic hydrogen production

In this study, graphitic carbon nitride (g-C₃N₄) was successfully coupled with TiO₂ using hydrothermal method, to develop an advanced heterojunction photocatalyst. The interaction between g-C₃N₄ and TiO₂ was confirmed through analysis of X-Ray spectroscopy (XPS) C 1s, N 1s, O 1s high resolution core level spectra of g-C₃N₄, TiO₂ and g–C₃N₄–TiO₂ heterojucntion. Further, through valence band spectra analysis, conduction band offset (0.12 eV) and valence band offset (0.28 eV) of g–C₃N₄–TiO₂ heterojunction were estimated. Also, composite material was identified as type II heterojunction between g-C₃N₄ and TiO₂. XRD, UV–vis, BET and HRTEM were employed to understand the changes in physicochemical properties. Photocatalytic hydrogen production rates were evaluated through water splitting experiments. Under visible light irradiation highest hydrogen production rate was achieved for g–C₃N₄–TiO₂ heterojunction sample with high content of TiO₂, and was about 1041 μmol/g.h. The improved photocatalytic activity of the heterojunction material was explained in detail.     

Interface excess on Sb-doped TiO2 photocatalysts and its influence on photocatalytic activity

Titanium dioxide (TiO₂) is a well-known photocatalyst that has been used in photocatalysis and has been studied as an alternative for artificial photosynthesis cells. Many works have tried doping this material with different elements to increase its photoactivity; however, a consequence of doping that has not received much attention is the segregation at the nanoparticle interfaces, such as the surface and the grain boundary (GB). In this study, Sb-doped TiO₂ nanoparticles have been produced by the polymeric precursor method, with the compositional range varying from 0 to 2 mol% Sb. The surface excess was measured by the surface lixiviation method, and the GB excess was calculated considering the total amount of Sb and its solubility in the TiO₂ bulk. The results showed that Sb interfacial segregation at both surface and GB increased the specific surface areas, reduced the crystallite sizes, increased the presence of the rutile phase, and changed the CO₂ adsorption, evidenced by DRIFT spectroscopy. The photoactivity was tested by the degradation of acetaminophen (ACT) under UV irradiation, revealing an increase of ~53% of activity for 0.05 mol% Sb-doped TiO₂ compared to undoped TiO₂.     

Microwave synthesis of magnetically separable ZnFe2O4-reduced graphene oxide for wastewater treatment

A magnetically separable ZnFe₂O₄-reduced graphene oxide (rGO) nano-composite was synthesised via a microwave method. Field emission scanning electron microscopy images of the nano-composite showed a uniform dispersion of nanoparticles on the rGO sheets. The performance of the nano-composite in wastewater treatment was assessed by observing the decomposition of methylene blue. The nano-composite showed excellent bifunctionality, i.e. adsorption and photocatalytic degradation of methylene blue, for up to five cycles of water treatment when illuminated with light from a halogen bulb. In contrast, water treatment with the nano-composite without illumination and the illuminated rGO, with no decoration of nanoparticles, diminished significantly after the first treatment. The reclamation of the ZnFe₂O₄-rGO nano-composite from treated water could be easily achieved by applying an external magnetic field.     

TiO_2/BiVO_4复合光催化剂的微波辅助水热法合成及催化性能研究

以硝酸铋和偏钒酸铵为原料,采用微波-辅助水热法合成了BiVO4和TiO2/BiVO4复合光催化剂,借助XRD、UV-Vis和FE-SEM等测试手段对样品进行表征。XRD分析表明,所得BiVO4粉体为单斜晶系,且与TiO2复合后,特征衍射峰宽化,强度降低;FE-SEM显示,所得样品为具有多级结构的球状纳米结构体系;UV-Vis吸收光谱表明,BiVO4粉体和TiO2/BiVO4在400～600 nm的可见光区域对光响应。根据光吸收特性,选择罗丹明B为模型污染物,考察了样品可见光催化活性。结果表明,TiO2/BiVO4相比BiVO4,具有更高的可见光催化活性。     

Controlled synthesis of Bi2O3/BiOBr/Zn2GeO4 heterojunction photocatalysts with enhanced photocatalytic activity

BiOBr/Zn₂GeO₄ heterojunctions decorated by Bi₂O₃ quantum dots (QDs; named as Bi₂O₃/BiOBr/Zn₂GeO₄ hereafter) with intriguing micro/nanostructures have been constructed via a two‐step hydrothermal route. The compositions, phases, and morphologies of Bi₂O₃/BiOBr/Zn₂GeO₄ were investigated in detail. The light absorption ability, photocurrent responses, and photocatalytic degradation of methylene blue (MB) experiments were performed to evaluate the photocatalytic activity of the micro/nanoheterostructured Bi₂O₃/BiOBr/Zn₂GeO₄, which present a degradation efficiency of 88% after 240 minutes under light irradiation (λ = 300‐600 nm) over 100 mg Bi₂O₃/BiOBr/Zn₂GeO₄ in a 100 mL, 4 mg/L MB solution. The photocatalytic performance could be retained for at least four runs, indicating its excellent reusability for the degradation of MB in aqueous solution. It is found that the photodegradation of MB over Bi₂O₃/BiOBr/Zn₂GeO₄ is mainly ascribed to a hole oxidation mechanism in combination with a superoxide oxidation process. The high photocatalytic performance of Bi₂O₃/BiOBr/Zn₂GeO₄ upon UV light irradiation can be attributed to the effective charge separation and smoothly transferring of the photogenerated charge carriers throughout the heterojunction. The feasible strategy of preparing Bi₂O₃/BiOBr/Zn₂GeO₄ ternary composites is also of benefit to fabricate other efficient heterojunction catalysts with specific morphologies and properties.     

In situ hydrothermal synthesis of Y-TiO2/graphene heterojunctions with improved visible-light-driven photocatalytic properties

The Y-TiO₂/graphene heterojunctions were prepared using a facile one-pot hydrothermal method. The SEM and TEM images showed that titanium dioxide and flaky graphene were tightly bound together, and XPS indicated that yttrium was doped uniformly into the complex. The crystal phase of titanium dioxide in Y-TiO₂/graphene composite was anatase, and the yttrium doping caused distortion of the titanium dioxide lattice, resulting in a new valence type and more defects. An appropriate amount of yttrium doping and graphene modification significantly improved the separation of photogenerated electron-hole pairs. In the degradation of rhodamine B, the co-modification of yttrium and graphene effectively improved the photocatalytic activity under visible and UV–vis light irradiation. With the amount of yttrium increasing, the photocatalytic activity of the Y-TiO₂/graphene complex first increased and reached the highest level of 40% and 63% for visible and ultraviolet-visible light, respectively, when the ratio of yttrium was increased to 1.0%. The enhancement of photocatalytic activity can be explained by the presence of yttrium ions increased the visible light absorption of titanium dioxide. Besides, the synergistic effect between yttrium ions and graphene effectively improved the separation rate of photoinduced electron-hole pairs.     

Microwave hydrothermal-reduction synthesis of zanthoxylum trunk-like Co/CoAl2O4/sepiolite nanocomposite

In this work, a novel Co/CoAl₂O₄/sepiolite nanocomposite was synthesized by reducing the CoAl₂O₄/sepiolite nanocomposite prepared via a microwave hydrothermal method. The effects of the content of sepiolite, types of the organic matters used, and their dosage on the microstructure of the CoAl₂O₄/sepiolite nanocomposite were investigated and the optimal conditions for fabricating the CoAl₂O₄/sepiolite nanocomposite were identified. Subsequently, the influence of the reduction temperature on the microstructure of the Co/CoAl₂O₄/sepiolite nanocomposite was studied. According to the various surface characterizations, the sample synthesized under the optimal conditions (i.e., with 10 vol% triethanolamine and 10 wt% sepiolite followed by the reduction at 650 °C for 3 h) showed spherical CoAl₂O₄ evenly dispersed on sepiolite nanofibers along with fine cobalt nanoparticles embedded on the surface of CoAl₂O₄. As a model reaction, Fischer-Tropsch synthesis was examined with the as-synthesized materials. The optimal sample has demonstrated a higher selectivity for C₅₊ (high-carbon hydrocarbons) and lower selectivity for CO₂, CH₄, and C₂–C₄ compared with the control sample. This work is believed to provide an effective strategy for low-cost batch fabrication of highly efficient supported cobalt-based catalysts with a novel transition layer where fine Co nanoparticles can be anchored with good dispersion.     

Efficient photocatalytic degradation of methylene blue over BiVO4/TiO2 nanocomposites

BiVO₄/TiO₂ nanocomposites were successfully synthesized by coupling the modified sol-gel method with hydrothermal method. The samples were physically characterized X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer, Emmett and Teller (BET)-specific surface area, UV–vis diffuse reflectance spectrophotometry, zeta potential, and photoluminescence techniques. The BiVO₄/TiO₂ nanocomposites exhibited good photocatalytic activity in degradation of methylene blue under simulated solar light irradiation. The photodegradation of methylene blue demonstrated that 0.5BiVO₄/0.5TiO₂ photocatalyst exhibited much enhanced photoactivity than pure BiVO₄ and TiO₂. Based on the obtained results, the as-prepare BiVO₄/ TiO₂ nanocomposite possessed great adsorptivity of methylene blue, extended light adsorption range, and efficient charge separation properties. Overall, this work could provide new insights into the fabrication of a BiVO₄/TiO₂ composite as high performance photocatalyst and promise as a solar light photocatalyst for dye wastewater treatment.