A novel Z-scheme Bi4O5I2/NiFe2O4 heterojunction photocatalyst with reliable recyclability for Rhodamine B degradation

Construction of heterojunction with reusability is one of the effective ways to avoid secondary pollution and strengthen photocatalysis. Herein, a magnetically recyclable Z-scheme Bi₄O₅I₂/NiFe₂O₄ heterojunction photocatalyst was successfully fabricated by a two-step hydrothermal method. Through adjusting the theoretical molar proportion of NiFe₂O₄ to Bi₄O₅I₂, it was verified that the optimal composite could decompose 98.5% Rhodamine B (RhB, 10 mg/L) within 60 min under simulative sunlight and 98.1% RhB within 80 min under visible light. According to the characterizations, the superior performance was mainly associated with the small band gap energy (2.44 eV) and efficient separation of photo-generated electrons and holes caused by the formation of heterojunction. Meanwhile, the enlarged specific area (27.6 m²/g) provided many adsorptive sites and active sites to improve the reaction further. Moreover, the trapping experiment indicated that the photodegradation involved O₂^–, OH and h⁺. After confirming the reliable activity, reusability and stability of the photocatalyst, an inferred mechanism was shown. In summary, the design of this magnetically recyclable Z-scheme Bi₄O₅I₂/NiFe₂O₄ heterojunction photocatalyst can become a new choice to purify wastewater.     

Exceptional photocatalytic activity for g-C3N4 activated by H2O2 and integrated with Bi2S3 and Fe3O4 nanoparticles for removal of organic and inorganic pollutants

Herein, hydrogen peroxide activated graphitic carbon nitride (agCN) was combined with Fe₃O₄ and Bi₂S₃ to fabricate agCN/Fe₃O₄/Bi₂S₃ nanocomposites via facile refluxing method, as visible-light-induced photocatalysts for photodegradations of anionic and cationic dyes such as MO, RhB, MB, and photoreduction of Cr(VI). The fabricated samples were explored by XRD, EDX, XPS, TGA, SEM, TEM, HRTEM, VSM, PL, FT-IR, BET, and UV-vis DRS. Photocatalytic activity of the nanocomposite with 20% of Bi₂S₃ was 16.6, 40.4, 19.5, and 12.5 times more than that of the pristine gCN in removal of RhB, MB, MO, and Cr(VI), respectively. A plausible photocatalytic mechanism on the agCN/Fe₃O₄/Bi₂S₃ nanocomposites was proposed by construction of n-n heterojunction between gCN and Bi₂S₃. Also, stability of the magnetic hybrid was characterized through cyclic photocatalytic tests.     

CuS纳米片修饰Bi5O7I复合材料用于光催化还原Cr(VI)水溶液

光催化技术以其高效、安全、低成本的优势,被广泛研究用于去除污水中有毒副作用的重金属Cr(VI).制备半导体复合材料是一种可以有效提高半导体光催化性能的途径.本研究通过简单的水热法合成了CuS纳米片修饰的Bi5O7I复合材料,并且表征和评估了其在可见光下对Cr(VI)的光催化还原活性.与纯Bi5O7I微米棒及纯CuS样品...     

Synthesis of carnation flower-like Bi2O2CO3 photocatalyst and its promising application for photoreduction of Cr(VI)

In this study, we have synthesized high-quality carnation flower-like Bi₂O₂CO₃ hierarchical architectures via a hydrothermal route. The as-synthesized Bi₂O₂CO₃ photocatalyst was systematically characterized and analyzed by various techniques. Its photocatalytic activity was investigated by simulated-sunlight driving photoreduction of Cr(VI), revealing that it exhibits excellent photocatalytic removal of Cr(VI). The effects of various factors (H₂SO₄, NaOH, Cr(VI) concentration, catalyst dosage) on the photoreduction efficiency and involved mechanism were systematically investigated and discussed. In addition, we have also systematically examined the effects of various parameters (H₂SO₄ concentration, 1,5-diphenylcarbazide (DPC) concentration, Cr(VI) concentration, reaction time t and reaction temperature T) on the absorbance of the Cr(VI) solution, with the aim of correctly determining the Cr(VI) concentration according to UV–vis absorption measurements using DPC as the chromogenic agent.     

Controlling the charge carriers recombination kinetics on the g-C3N4-BiSI n-n heterojunction with efficient photocatalytic activity in N2 fixation and degradation of MB and phenol

The challenges like the photocatalytic reduction of N₂ and elimination of contaminants from the wastewater are accessible by low cost, stable, and visible-light-driven semiconductor-based photocatalysis. A novel g-C₃N₄/BiSI nanocomposite was synthesized by hydrothermal method and applied for the first time in photocatalytic nitrogen fixation and degradation of methylene blue dye and phenol. The physicochemical features of the photocatalysts were studied by XRD, XPS, FTIR, BET, DRS, FESEM, TEM, EDX mapping, PL, EIS, Mott-Schottky, and photocurrent techniques. Experimental results showed that the production of ammonia in the presence of g-C₃N₄/BiSI nanocomposite was 1280 μmol L^?1 g^?1, while this values for g-C₃N₄ and BiSI were 274 μmol g^?1 L^?1 and 126 μmol g^?1 L^?1, respectively. Moreover prepared nanocomposite exhibited a higher rate constant in the MB (537.5 × 10^?4 min^?1) and phenol (353 × 10^?4 min^?1) degradation compared with the counterparts. The charge separation efficiency obviously improved, which was ascribed to the charges migration between g-C₃N₄ and BiSI in an n-n heterojunction system. In addition, high specific surface area and strong visible light absorption were identified as other factors affecting photocatalytic performance. This unique heterojunction photocatalyst has wide application prospects in environmental treatment.     

Facile synthesis of Ti3C2 MXene-modified Bi2.15WO6 nanosheets with enhanced reactivity for photocatalytic reduction of Cr(VI)

Through a facile hydrothermal method, we have successfully prepared Ti₃C₂/Bi_2.15WO₆ (TC/BWO) composite, and systematically investigated their reactivity for the photocatalytic reduction of Cr(VI) under visible light. X-ray diffraction and Raman analysis confirm the formation of heterostructure between Bi_2.15WO₆ and Ti₃C₂. The resultant 7TC/BWO composite exhibits enhanced photoactivity toward Cr(VI) reduction. After 120 min irradiation, the conversion of Cr(VI) reaches 92.5% with the quasi-first-order kinetic constant of k = 0.0145 min^?1, which is higher than that of pure BWO (30% and k = 0.0005 min^?1). The electrochemical and photoluminescent characterization confirm that the introduction of Ti₃C₂ is conducive to the separation of carriers, thus significantly improves the photocatalytic performance of TC/BWO. Furthermore, the radical capture experiments verify that the electrons are important for enhancing reduction of Cr(VI) to Cr(III). As a result, this research provides a comprehensive understanding of the reduction of Cr(VI) by TC/BWO composite under visible light.     

Fabrication of Bi2WO6/In2O3 photocatalysts with efficient photocatalytic performance for the degradation of organic pollutants: Insight into the role of oxygen vacancy and heterojunction

Photocatalysis is an attractive and green strategy for organic pollutant removal. The development of alternative and effective photocatalysts has attracted great attention. Herein, we rationally engineer an alternative rich-oxygen vacancies (OVs) Bi₂WO₆/In₂O₃ composite photocatalyst via integrating the calcination and hydrothermal method for removing organic dyes (rhodamine B). Thanks to the synergistic effect of OVs and heterojunction structure, the 80 wt% Bi₂WO₆/In₂O₃ (BiIn80) displays enhanced photocatalytic degradation effect. The degradation rate of BiIn80 is up to 97.3% under light irradiation within 120 min and the reaction rate constant k value (0.03221 min⁻¹) is about 15-fold and 4.17-fold as high as those of In₂O₃ (0.00203 min⁻¹) and Bi₂WO₆ (0.00772 min⁻¹), respectively. The heterostructure of Bi₂WO₆/In₂O₃ can extend the lifespan of the photogenerated charge carriers. Moreover, the density functional theory (DFT) calculations reveal that the OVs in Bi₂WO₆/In₂O₃ can boost visible light absorbability by decreasing band gap value and serve as the extra electron transfer channels to enhance the separation efficiency of photogenerated electron-hole pairs. This study not only provides an alternative route for fabricating highly efficient heterojunction photocatalysts, but also obtains better understanding of the synergistic effect of OVs and heterojunction on enhancing the photocatalytic performance.     

BiOBr and BiOCl decorated on TiO2 QDs: Impressively increased photocatalytic performance for the degradation of pollutants under visible light

BiOBr and BiOCl were decorated on TiO₂ QDs through n-p-p heterojunctions by a simple strategy and they were applied for degradation of three organic dyes upon visible illumination. The obtained photocatalysts were analyzed via XRD, FESEM, EDX, UV–vis DRS, PL, BET, TEM, HRTEM, FT-IR, EIS, XPS, and transient photocurrent measurements. The TiO₂ QDs/BiOBr/BiOCl nanocomposite with 20% wt. of BiOBr and 30% wt. of BiOCl displayed superior photoability in the degradation of methylene blue, rhodamine B, and fuchsine, which was almost 34.5, 176, and 78.7-times larger than TiO₂ and 27.8, 13.5, and 51.5-folds greater than TiO₂ QDs, respectively. The results show that the construction of intimate n-p-p heterojunctions between BiOBr, TiO₂ QDs, and BiOCl counterparts leads to enhanced visible-light harvesting and improved charge separation, resulted efficiently increased photocatalytic activity. The trapping results proved that h⁺, ^•O₂⁻, and OH^• species have considerable effects on the degradation reaction. We think that the improved efficiency of the ternary TiO₂ QDS/BiOBr/BiOCl photocatalyst is a splendid alternative for the removal of toxic contaminants from wastewater.     

Integration g-C3N4 nanotubes and Sb2MoO6 nanoparticles: Impressive photoactivity for tetracycline degradation,Cr (VI) reduction,and organic dyes removals under visible light

The development of high-efficiency photocatalysts is an attractive strategy for pollutants degradation under visible light. Herein, novel photocatalysts are reported through coupling Sb₂MoO₆ with g-C₃N₄ nanotube (abbreviated as GCN nanotube) by a simple reflux method. Also, the nanocomposites were defined by applying various analyses. Under visible-light excitation, the GCN nanotube/Sb₂MoO₆ systems had more photoactivity than g-C₃N₄ (abbreviated as GCN) and the rate constant for RhB removal on optimal GCN nanotube/Sb₂MoO₆ (30%) nanocomposite was 48.3 times premier than the GCN. Also, compared to the pristine GCN, the GCN nanotube/Sb₂MoO₆ (30%) sample demonstrated supreme photoactivity towards tetracycline degradation and Cr (VI) photoreduction, which was 88.5 and 21.8 times higher than the bulk GCN, respectively. These impressive enhancements were attributed to the quick segregation of charge carriers, boosted visible-light absorption, and extended specific surface area. Moreover, the photocatalyst has enough activity after four successive cycles. Finally, a conceivable charges transfer route is presented through n-n heterojunction constructed between Sb₂MoO₆ and GCN nanotube.     

硅藻土原位生长Nb2O5纳米棒及表面Cr(VI)吸附转化行为研究

以活化铌酸为铌源, 草酸铵为沉积剂, 十二烷基苯磺酸钠为模板剂, 采用水热法在硅藻土表面原位生长Nb₂O₅纳米棒。采用SEM、TEM、XRD、BET、FT-IR和XPS等分析方法对样品进行表征, 反应14 h后, Nb₂O₅纳米棒长度为500~700 nm, 直径为25~35 nm; 硅藻土原位生长Nb₂O₅纳米棒样品比表面积为157 m²/g。研究了样品对Cr(VI)的吸附与光还原行为, 可见光条件下对Cr(VI)吸附量可达220 mg/g; 紫外光条件下, 可将表面吸附的Cr(VI)转变为Cr(III), 样品经过5次循环使用后, 对Cr(VI)(100 mg/L)降解率仍能保持在93%左右。样品可对重金属污染废水中Cr(VI)进行吸附与毒性降解一体化去除。     

Recyclable and highly efficient photocatalytic fabric of Fe(III)@BiVO4/cotton via thiol-ene click reaction with visible-light response in water

In this article, we designed a photocatalytic cotton fabric of Fe(III)@BiVO₄/cotton via thiol-ene click reaction and achieved an enhanced photocatalytic performance and excellent recyclability under visible-light irradiation. The Fe(III)@BiVO₄ and cotton fabric were modified with KH570 (including CC groups) and KH580 (including SH groups), respectively. Then, the Fe(III)@BiVO₄/KH570 and KH580/cotton reacted and connected via thiol-ene click reaction, which can effectively solve its recyclability in practical application and realize ideal all-in-one structure. The as-prepared Fe(III)@BiVO₄/cotton not only exhibited an excellent photocatalytic performance in reducing Cr(VI) to Cr(III), but also showed a remarkable performance in degradation of C.I. reactive blue 19 (RB-19) under visible-light. Meanwhile, various analysis technique were used to confirm the successful connection between Fe(III)@BiVO₄ and cotton fabric via thiol-ene click reaction. Moreover, the photocatalytic mechanism was also discussed comprehensively in view of trapping experiments and ESR analysis.     

Multiple heterojunction system of Bi2MoO6/WO3/Ag3PO4 with enhanced visible-light photocatalytic performance towards dye degradation

Multiple heterojunction system of Bi₂MoO₆/WO₃/Ag₃PO₄ was designed via constructing binary heterojunction Bi₂MoO₆/WO₃, followed by the deposition of nano-Ag₃PO₄ on the surface of Bi₂MoO₆/WO₃. Various techniques were employed to characterize the properties of the as-prepared catalytic system. In this study, the decomposition efficiency of C.I. reactive blue 19 (RB-19) was used as a measure of photocatalytic activity and the Bi₂MoO₆/WO₃/Ag₃PO₄ composite exceeded its stand-alone components (pristine Ag₃PO₄, WO₃/Ag₃PO₄ and Bi₂MoO₆/Ag₃PO₄) by 3.16 times, 2.63 times and 1.75 times, respectively. The photocatalytic tests implied that the construction of multiple heterojunction could achieve efficient separation of photo-generated electrons and holes. A possible photocatalytic mechanism for Bi₂MoO₆/WO₃/Ag₃PO₄ system was also proposed according to the results of trapping experiments.     

La掺杂对Sr2Bi4Ti5O18铁电陶瓷性能的影响

利用传统的固相烧结工艺制备了Sr2LaxBi1-xTi5O18(x=0．00、0．05、0．1、0．25、0．5、0．75、1．00)陶瓷样品。用X射线衍射对其微结构进行了分析．并测量了其铁电、介电性能。X射线衍射结果表明La掺杂对Sr2Bi4TixO18的晶体结构几乎没有影响。样品的铁电、介电结果表明。随着La掺杂量的增加，样品的剩余极化(2Pr)和矫颈场(Ec)逐渐减小。这是由于离子半径较大的La取代类钙钛矿层A位Bi离子。使得样品晶格畸变变小，从而导致2Pr降低。晶格畸变的减小也使得沿着外电场方向氧八面体中的阳离子更易运动。导致Ec减小。样品的相变温度L随着La含量的增加而降低。这也与样品晶格畸变有关。     

晶化时间对水热法制备钛酸铋纳米粉体的研究

采用分析纯Bi(NO3)3·5H2O和TiCl4为原料,以NaOH为矿化剂,在反应温度为230℃的水热条件下,研究了晶化时间对Bi4Ti3O12物相结晶性能的影响。XRD表明在晶化时间不少于240min的条件下,才能合成纯的Bi4Ti3O12单一物相,并随着晶化时间的延长,Bi4Ti3O12的晶粒有所长大。通过红外光谱、比表面积和TEM等性能表征,探讨了钛酸铋的水热合成机理,用原位生成机理和溶解 再结晶机理解释了钛酸铋的水热生长过程。     

High performance magnetically recoverable g-C3N4/Fe3O4/Ag/Ag2SO3 plasmonic photocatalyst for enhanced photocatalytic degradation of water pollutants

The g-C₃N₄/Fe₃O₄/Ag/Ag₂SO₃ nanocomposites have been successfully fabricated by facile refluxing method. The as-obtained products were characterized by XRD, EDX, SEM, TEM, UV–vis DRS, FT–IR, TGA, PL, and VSM techniques. The results suggest that the Ag/Ag₂SO₃ nanoparticles have anchored on the surface of g-C₃N₄/Fe₃O₄ nanocomposite, showing strong absorption in the visible region. The evaluation of photocatalytic activity indicates that for the g-C₃N₄/Fe₃O₄/Ag/Ag₂SO₃ (40%) nanocomposite, the degradation rate constant was 188 × 10^?4 min^?1 for rhodamine B, exceeding those of the g-C₃N₄ (16.0 × 10^?4 min^?1) and g-C₃N₄/Fe₃O₄ (20.2 × 10^?4 min^?1) by factors of 11.7 and 9.3, respectively. The results showed that the nanocomposite prepared by refluxing for 120 min has the superior photocatalytic activity and its activity decreased with rising the calcination temperature. The trapping experiments confirmed that superoxide ion radical was the main active species in the photocatalytic degradation process. Also, it was demonstrated that the magnetic photocatalyst has considerable activity in degradation of one more dye pollutant. Finally, the reusability of the photocatalyst was evaluated by five consecutive catalytic runs. This work may open up new insights into the utilization of magnetically separable nanocomposites and provide new opportunities for facile fabrication of g-C₃N₄-based plasmonic photocatalysts.     

Photocatalytic activity of pulsed laser deposited TiO2 thin films in N2, O2 and CH4

We report on pulsed laser deposition of TiO₂ films on glass substrates in oxygen, methane, nitrogen and mixture of oxygen and nitrogen atmosphere. The nitrogen incorporation into TiO₂ lattice was successfully achieved, as demonstrated by optical absorption and XPS measurements. The absorption edge of the N-doped TiO₂ films was red-shifted up to ∼ 480 nm from 360 nm in case of undoped ones.The photocatalytic activity of TiO₂ films was investigated during toxic Cr(VI) ions photoreduction to Cr(III) state in aqueous media under irradiation with visible and UV light. Under visible light irradiation, TiO₂ films deposited in nitrogen atmosphere showed the highest photocatalytic activity, whereas by UV light exposure the best results were obtained for the TiO₂ structures deposited in pure methane and oxygen atmosphere.     

Synthesis and characterization of Bi2MoO6/MIL-101(Fe) as a novel composite with enhanced photocatalytic performance: Effect of water matrix and reaction mechanism

The integration of Bi₂MoO₆ with MIL-101(Fe) as a novel structure enhanced photocatalytic activity for RhB degradation. Bi₂MoO₆/MIL-101(Fe) composites were synthesized via the solvothermal procedure and characterized by XRD, EDX, FE-SEM, TEM, FT-IR, BET, TGA, UV–vis DRS, and PL. The optimal molar ratio Bi₂MoO₆:MIL-101(Fe) equal to 1:1 showed better photocatalytic activity than Bi₂MoO₆ and MIL-101(Fe) and other heterostructure composites. The effect of pH (5–9), reaction time (60–120 min), catalyst concentration (0.1–0.5 g/L), and dye concentration (10–20 ppm) were investigated on the removal performance of RhB by using central composite face-centered (CCF). In the optimal process factors where the [Catalyst]:0.4 g/L, [RhB]:20 ppm, pH: 6.5, irradiation time: 120 min, the RhB and TOC removal efficiency were 85% and 84.2%, respectively. The holes and superoxide radicals played a major role in the degradation of RhB. The addition of salt (NaCl, Na₂SO₄, and NaHCO₃) at different concentrations (100, 200, 400, and 800 ppm) revealed that the salts have an inhibitory role in the photocatalytic performance. At low concentrations of 100 ppm, the salts had a negative effect on removal efficiency (k_{Pure water} = 0.0155 min^?1, k_NaCl = 0.0075 min^?1, k_Na2SO4 = 0.0132 min^?1, k_NaHCO3 = 0.006 min^?1). Increasing the salt concentration to 800 ppm caused improved efficiency for NaCl (k_NaCl = 0.0141 min^?1), while for Na₂SO₄ this trend was decreasing (k_Na2SO4 = 0.011 min^?1), and for NaHCO₃ sharply diminished (k_NaHCO3 = 0.0026 min^?1).     

Simultaneous separation and speciation of inorganic As(III)/As(V) and Cr(III)/Cr(VI) in natural waters utilizing capillary microextraction on ordered mesoporous Al2O3 prior to their on-line determination by ICP-MS

In this paper, a system of flow injection (FI) capillary microextraction (CME) on line coupled with inductively plasma mass spectrometry (ICP-MS) was proposed for simultaneous separation and speciation of inorganic As(III)/As(V) and Cr(III)/Cr(VI) in natural waters. Ordered mesoporous Al2O3 coating was prepared by sol-gel technology and used as CME coating material. Various experimental parameters affecting the capillary microextraction of inorganic arsenic and chromium species have been investigated and optimized. Under the optimized conditions, the limits of detection were 0.7 and 18 ng L(-1) for As(V) and Cr(VI), 3.4 and 74 ng L(-1) for As(III) and Cr(III), respectively, with an enrichment factor of 5 and a sampling frequency of 8h(-1). The relative standard deviations (R.S.D.) were 3.1, 4.0, 2.8 and 3.9% (C=1 ng mL(-1), n=7) for As(V), As(III), Cr(VI) and Cr(III), respectively. The proposed method was successfully applied for the analysis of inorganic arsenic and chromium species in mineral water, tap water and lake water with the recovery of 94-105%. In order to verify the accuracy of the method, two certified reference of GSBZ50027-94 and GSBZ50004-88 water samples were analyzed and the results obtained were in good agreement with the certified values. The ordered mesoporous Al2O3 coated capillary showed an excellent solvent and thermal stability and could be re-used for more than 30 times without decreasing extraction efficiency.     

快速退火工艺条件下温度对Bi4Ti3O12铁电薄膜微观结构与性能的影响

采用快速退火工艺在Pt/Ti/SiO2/p-Si衬底上制备了Bi4Ti3O12铁电薄膜.研究了退火温度对薄膜微观结构、铁电特性及介电性能的影响.研究表明:退火温度对Si基Bi4Ti3O12铁电薄膜晶相结构的影响显著,对晶粒尺寸和表面形貌的影响较小,但退火温度超过800℃后会出现焦绿石等杂相;低于750℃时,薄膜的剩余极化随退火温度升高而增大,高于750℃时却有所减小,但矫顽电场随退火温度升高而逐渐降低;退火温度对薄膜的漏电流密度有一定的影响,薄膜的漏电流密度在200kV/cm极化电场作用下低于3×10-9A/cm2,750℃时的剩余极化和矫顽电场分别为11μC/cm2和77kV/cm,具有较好的铁电和介电性能.     

Enhanced photocatalytic degradation performance of organic contaminants by heterojunction photocatalyst BiVO4/TiO2/RGO and its compatibility on four different tetracycline antibiotics

Photocatalytic performance of four tetracycline antibiotics using BiVO₄/TiO₂/RGO composites was investigated. To make full use of catalysis, optimum preparation conditions involved RGO content, solution pH and hydrothermal temperature on the structure forming of BiVO₄/TiO₂/RGO composites were investigated. Subsequently, the obtained visible light-driven photocatalyst was used to degrade four kinds of tetracycline antibiotics involved tetracycline (TC), chlortetracycline (CTC), oxytetracycline (OTC) and doxycycline (DXC) for wastewater treatment. Results showed that BiVO₄/TiO₂/RGO photocatalyst exhibited excellent photocatalytic activity and high compatibility due to the enhanced separation efficiency of photo-generated carriers with high reduction and oxidation capability. The degradation process of four kinds of tetracycline antibiotics was traced and detected through identifying intermediates produced in the reaction system. And a possible catalytic mechanism for BiVO₄/TiO₂/RGO photocatalyst was put forward based on band gap structure of BiVO₄ and TiO₂.