Enhanced and suppressed effects of ionic liquid on the photocatalytic activity of TiO2

The effects of a room temperature ionic liquid, 1-butyl-3-methylimidazolium terafluoroborate ([Bmim]BF₄), on the photocatalytic performance of Degussa P25 TiO₂ were investigated. Also, the photocatalysis mechanism was systematically analyzed by conducting different reactive radical trapping experiments. The results showed that photogenerated electrons were the main reactive species involved in the photocatalytic degradation of methyl orange (MO), while ?OH radicals and photogenerated holes played an important role in the photocatalytic decomposition of rhodamine B (RhB). The addition of ionic liquid (IL) could slightly enhance the photocatalytic degradation rate of MO because adsorption of [Bmim]⁺ ions on the TiO₂ surface not only enhanced traping and transfer of photogenerated electrons, but also facilitated adsorption of negatively charged MO. On the contrary, IL suppressed the degradation rate of RhB because [Bmim]⁺ on the TiO₂ surface not only hindered the access of positively charged RhB to TiO₂, but also restricted the diffusion of positively charged holes to the TiO₂/solution interface.     

掺镁钛酸钡纳米棒的水热合成和光催化性能

用水热法制备掺镁钛酸钡(Ba1-xMgxTiO3(x=0,0.10,0.20,0.30,0.40),BMT)纳米粉体。运用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、紫外可见漫反射光谱技术(DRS)等手段对样品进行了表征,并在可见光照射下于溶液中考察了其光催化降解甲基橙反应活性。结果表明,通过控制氢氧根浓度可以得到不同形貌的纳米粉体。基于不同条件下制备的样品的微结构分析,提出了这些不同形貌的形成机制。制备出的BMT材料的带隙能约为2.61 eV。光催化反应结果表明BMT的光催化活性比掺氮TiO2高得多。OH-浓度为8 mol·L-1时制备的BMT纳米棒光催化效率最高,经可见光照射360 min,浓度为0.01 mmol·L-1甲基橙溶液的降解率可达到93.0%,且循环使用4次后,其光催化活性并没有明显降低,表明BMT是一种稳定有效的可见光催化剂.     

不同形貌Bi4Ti3O12粒子的可控合成及光催化性能

研究了用一步水热法制备的不同形貌的钛酸铋(Bi₄Ti₃O₁₂, BIT)粒子的光学和可见光催化性能, 并对其晶体结构和微观结构用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段进行了表征. XRD结果表明, 所制备的BIT 样品为层状钙钛矿结构. FESEM结果表明, 通过控制水热过程的反应参数可以得到不同形貌的纳米粒子. 紫外-可见漫反射光谱(UV-Vis DRS)表明BIT 样品的带隙能约为2.88-2.93 eV. 利用可见光(λ>420 nm)照射下的甲基橙(MO)降解实验评价了BIT 样品的光催化性能. 结果表明, BIT 的光催化活性比掺氮TiO₂ (N-TiO₂)高得多. 研究了形貌对BIT 光催化性能的影响. 所制备的BIT纳米带光催化效率最高, 经可见光照射360 min, 甲基橙溶液的降解率可达到95.0%.     

异质型BiOI/NaBiO3光催化剂的合成及其光催化性能

根据表面化学蚀刻原理采用加热冷凝回流的方法制备了一系列组成的异质结构BiOI/NaBiO₃光催化剂.利用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)和紫外-可见漫反射光谱(UV-Vis-DRS)等技术对其晶相结构、微观形貌和光吸收性能进行了表征.光催化实验表明,BiOI/NaBiO₃在可见光下可以有效降解罗丹明B(RhB),当BiOI与NaBiO₃的物质的量分数为一定值时,异质结构的光催化剂明显优于单一组分的光催化活性.通过加入不同的牺牲剂及荧光实验结果推测了该异质结构材料的光催化机理,并且分析了其光生载流子的传输方向及光催化过程的活性物种.研究表明,BiOI/NaBiO₃的催化活性增强主要归结为两者之间形成了有效的异质结构,其内建电场能够促进光生载流子的分离,同时光生空穴h⁺在光催化降解过程中是主要的活性物种.     

Enhancing the photocatalytic activity of Ga2O3–TiO2 nanocomposites using sonication amplitudes for the degradation of Rhodamine B dye

A Ga₂O₃–TiO₂ photocatalyst was synthesized by a mechanomixing method followed by a sonication technique using different amplitudes of sonication (0%, 25%, 50%, and 75% of 20 kHz). The prepared photocatalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared, Brunauer–Emmett–Teller (BET) surface area (S_BET), zeta potential, and optical techniques. Ga₂O₃–TiO₂ exhibited an excellent photocatalytic activity for Rhodamine B (RhB) dye degradation under UV irradiation. The RhB degradation rate rose linearly with the increase of sonication amplitude. The photodegradation rate (k) of the synthesized samples was calculated according to the Langmuir–Hinshelwood kinetic expression. It reached a maximum of 5.25 × 10⁻² min⁻¹ with R² of 0.99 for Ga₂O₃–TiO₂ (75%) photocatalysts. The main reactive species were detected through radical scavenging experiments. The formation of hole reactive species is the rate-determining step in the case of Ga₂O₃–TiO₂ (75%) photocatalysts.     

Visible-light-driven Oxygen Vacancy and Carbon Doping of C@TiO2-x Photocatalyst for Enhanced Pollutants Degradation Performance

Oxygen Vacancy (OVs) and carbon doping of the photocatalyst body will significantly enhance the photocatalytic efficiency. However, synchronous regulation of these two aspects is challenging. In this paper, a novel C@TiO_2-x photocatalyst was designed by coupling the surface defect and doping engineering of titania, which can effectively remove rhodamine B (RhB) and has a relatively high performance with wide pH range, high photocatalytic activity and good stability. Within 90 minutes, the photocatalytic degradation rate of RhB by C@TiO_2-x (94.1 % at 20 mg/L) is 28 times higher than that of pure TiO₂. Free radical trapping experiments and electron spin resonance techniques reveal that superoxide radicals (⋅O²⁻) and photogenerated holes (h⁺) play key roles in the photocatalytic degradation of RhB. This study demonstrates the possibility of regulating photocatalysts to degrade pollutants in wastewater based on an integrated strategy.     

Template‐Free Fabrication of Bi2O3 and (BiO)2CO3 Nanotubes and Their Application in Water Treatment

Uniform bismuth oxide (Bi₂O₃) and bismuth subcarbonate ((BiO)₂CO₃) nanotubes were successfully synthesized by a facile solvothermal method without the need for any surfactants or templates. The synergistic effect of ethylene glycol (EG) and urea played a critical role in the formation of the tubular nanostructures. These Bi₂O₃ and (BiO)₂CO₃ nanotubes exhibited excellent Cr^VI‐removal capacity. Bi₂O₃ nanotubes, with a maximum Cr^VI‐removal capacity of 79 mg g^?1, possessed high removal ability in a wide range of pH values (3–11). Moreover, Bi₂O₃ and (BiO)₂CO₃ nanotubes also displayed highly efficient photocatalytic activity for the degradation of RhB under visible‐light irradiation. This work not only demonstrates a new and facile route for the fabrication of Bi₂O₃ and (BiO)₂CO₃ nanotubes, but also provides new promising adsorbents for the removal of heavy‐metal ions and potential photocatalysts for environmental remediation.     

Degradation of rhodamine B photocatalyzed by Eu-doped CdS nanowires illuminated by visible radiation

CdS nanowires doped with different contents of Eu dopant were synthesized by solvothermal method. XRD, SEM, TEM and Raman analyses certified that the as-synthesized samples were hexagonal CdS uniform nanowires. The pure CdS nanowires were 1–3 ?μm long and 80 ?nm diameter with the 1st and 2nd order longitudinal phonon modes at 298 and 594 ?cm^?1. The 3% Eu-doped CdS wires were 800 ?nm–2.5 ?μm long and 75 ?nm diameter with the 1st and 2nd order longitudinal phonon modes at 296 and 593 ?cm^?1. CdS nanowires grew along the [001] direction due to the surface energy effect. The photocatalytic properties of CdS and Eu-doped CdS nanowires were investigated for the degradation of rhodamine B (RhB) illuminated by visible radiation. In this research, Eu dopant played the role in promoting the photocatalytic kinetics because Eu³⁺ ions act as an electron acceptor to promote charge separation and photocatalytic activity. Both ^●OH and ^●O₂^? were the main active radicals used to transform RhB molecules into CO₂, H₂O and other intermediates.     

Z-scheme TiO2/g-C3N4 composites prepared by hydrothermal assisted thermal polymerization with enhanced visible light photocatalytic activity

Melamine was added to the precursor of TiO₂, then TiO₂ prepared by hydrothermal, while melamine was modified. Subsequently, a series of Z-scheme TiO₂/g-C₃N₄ heterojunction composites were successfully synthesized by simple calcination. The morphology and structure of samples were characterized by XRD, FT-IR, UV–vis DRS, SEM, TEM, PL and BET. The photocatalytic activity of these samples has been investigated by degradation of Rhodamine B (RhB), and results indicated that photocatalytic activity of the as-prepared samples was greatly influenced by the content of titanium tetrabutoxide in precursors and the hydrothermal time. The degradation rate of TiO₂/g-C₃N₄-1 to RhB was the best, which was 5.05-fold of pure TiO₂ (19.61%) and 2.25-fold of bulk g-C₃N₄ (44.06%), respectively. The trapping experiment results showed that ^·O₂^? and h⁺ were main active species during degradation of RhB. The photocatalytic activity of the sample did not decrease significantly after 4 cycles. The unique Z-scheme heterojunction between TiO₂ and g-C₃N₄ improved photocatalytic activity of the samples under visible light.

     

Bi3.25Sm0.75Ti3O12纳米线的水热合成及可见光催化性能

用一步水热法制备了直径约为40 nm的Bi3.25Sm0.75Ti3O12(BSmT)纳米线。BSmT纳米线为层状钙钛矿结构。紫外可见漫反射光谱表明,制备出的BSmT材料的带隙能约为2.67 eV。催化反应结果表明,BSmT的光催化活性比掺氮TiO2(N-TiO2)和纯相钛酸铋(Bi4Ti3O12,BIT)高得多,经可见光照射360 min,浓度为0.01 mmol.L-1甲基橙溶液的降解率可达到92.0%。BSmT光催化剂具有更高催化活性的原因是Sm3+离子掺杂拓展了BIT对可见光的吸收范围,同时抑制了BIT的光生电子-空穴的复合。并且BSmT光催化剂经循环使用4次后,其光催化活性并没有明显降低,表明BSmT是一种稳定有效的可见光催化剂。     

Synthesis of Co2+-doped Fe2O3 photocatalyst for degradation of pararosaniline dye

In this paper, x (=2, 5, 7 and 10mol%) Co²⁺-doped Fe₂O₃ (xCo:Fe₂O₃) nanoparticles with enhanced photocatalytic activity have been reported. xCo:Fe₂O₃ nanoparticles were successfully prepared by co-precipitation followed thermal decomposition method. The structural, optical and morphological properties of the prepared samples were studied by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), diffuse reflectance (DR) UV–visible absorption spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained results revealed that Co²⁺ ions were well doped within the lattices of Fe₂O₃. Also, Co²⁺ ions suppress the formation of the most stable α- Fe₂O₃ and stabilize less stable γ-Fe₂O₃ at 450 °C. The photocatalytic activity of xCo:Fe₂O₃ was examined by using pararosaniline (PR) dye. It was found that photocatalytic degradation of PR depends on dopant concentration (Co²⁺ ions). Relatively, the highest photocatalytic activity was observed for 5%Co:Fe₂O₃ nanoparticles. The plausible photocatalytic degradation pathway of PR at xCo:Fe₂O₃ surface has also been proposed.     

ZnO修饰提升花状BiOBr的可见光催化降解罗丹明B性能

以Bi(NO3)3·5H2O、Zn(CH3COO)2·2H2O和NaBr为前驱体,采用简单溶剂热法制备BiOBr/ZnO三维花状微纳米复合材料.采用X射线衍射、扫描电子显微镜、X射线光子能谱、N2吸附-脱附、光致发光和电子顺磁共振等分析技术对其理化性质进行了表征.通过可见光催化降解罗丹明B(RhB)的实验测试了复合材料...     

PVA在提高TiO2/CdSe异质结光催化活性与抗光腐蚀性能方面的应用及机理

通过阳极氧化法和电化学沉积制备了TiO_2/CdSe异质结膜,并通过旋涂结合后续热处理的方法,在TiO_2/CdSe异质结膜上制备适量脱水态的聚乙烯醇(PVA)来提高TiO_2/CdSe异质结抗光腐蚀性能。采用XRD,SEM,FTIR,UV-Vis,PL,电化学测试,光催化降解罗丹明B等方法对样品的晶体结构、微观形貌、光电化学性能、光催化性能等进行了表征,并通过测定光降解体系中Cd2+的浓度,研究了纳米复合材料的抗光腐蚀性能。结果表明,与TiO_2/CdSe相比,TiO_2/CdSe/PVA纳米复合材料不仅具有更好的可见光光催化活性,还具有良好的可见光光催化稳定性和抗光腐蚀性能。同时,PVA的存在对光催化反应中的二次污染物Cd2+也有抑制作用。     

Enhancing the Photocatalytic Activity of Sr4Al14O25: Eu2+, Dy3+ Persistent Phosphors by Codoping with Bi3+ Ions

The photocatalytic activity of Bismuth‐codoped Sr₄Al₁₄O₂₅: Eu²⁺, Dy³⁺ persistent phosphors is studied by monitoring the degradation of the blue methylene dye UV light irradiation. Powder phosphors are obtained by a combustion synthesis method and a postannealing process in reductive atmosphere. The XRD patterns show a single orthorhombic phase Sr₄Al₁₄O₂₅: Eu²⁺, Dy³⁺, Bi³⁺ phosphors even at high Bismuth dopant concentrations of 12 mol%, suggesting that Bi ions are well incorporated into the host lattice. SEM micrographs show irregular micrograins with sizes in the range of 0.5–20 μm. The samples present an intense greenish‐blue fluorescence and persistent emissions at 495 nm, attributed to the 5d–4f allowed transitions of Eu²⁺. The fluorescence decreases as Bi concentration increases; that suggest bismuth‐induced traps formation that in turn quench the luminescence. The photocatalytic evaluation of the powders was studied under both 365 nm UV and solar irradiations. Sample with 12 mol% of Bi presented the best MB degradation activity; 310 min of solar irradiation allow 100% MB degradation, whereas only 62.49% MB degradation is achieved under UV irradiation. Our results suggest that codoping the persistent phosphors with Bi³⁺ can be an alternative to enhance their photocatalytic activity.     

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.

     

Synthesis of ZnTiO3/tourmaline/Ni foam catalyst and enhanced photocatalytic performance

ZnTiO₃/tourmaline loaded on the nickel foam (ZnTiO₃/tourmaline/Ni-foam) is prepared by a facile coating method. Morphology and structure of the photocatalyst were characterized by X-ray diffraction (XRD), scanning electrons microscopy (SEM), raman spectroscopy, UV–vis diffuse reflectance spectrum (UV–vis DRS) and photoluminescence spectroscopy (PL). The photocatalytic properties of the materials were tested by using the Rhodamine B (RhB) solution as the target pollutant. The results indicates that the ZnTiO₃/tourmaline/Ni foam exhibited higher photocatalytic activity than that of ZnTiO₃ and ZnTiO₃/Ni foam under ultraviolet (UV) light irradiation, and its degradation rate was up to 99.2%. Moreover, the degradation rate remained at 91.3% after eight consecutive photocatalytic reaction cycles. The outstanding photocatalytic performances of ZnTiO₃/tourmaline/Ni foam was mainly attributed to the existence of tourmaline, which can help to inhibit the recombination of electron-hole paris, and the proper pore structure of the carrier. Meanwhile, the trapping experiments indicated that ·O₂^– was the main active species in the photocatalytic degradation of RhB.     

Recyclable MoO3 nanobelts for photocatalytic degradation of Rhodamine B by near infrared irradiation

Molybdenum trioxide (MoO₃) represented an excellent photocatalytic performance with many applications, including degradation of organic contaminants and splitting of water. This paper presented a new route to synthesize MoO₃ nanobelts with high aspect ratios and crystallinity by a hydrothermal technique. This work showed that the as-synthesized nanobelts exhibited strong photocatalytic activity to degrade an organic dye of Rhodamine B (RhB) in aqueous solution under the exposure of the light source in the near infrared wavelength range, significantly improving the photocatalytic activity of the nanobelts. The results also showed that for a small concentration of RhB at 7.5 mg/L a complete photodegradation (for a given MoO₃ nanobelts quantity of 0.1 g) can be reached after exposing for 60 min. For all concentrations of the RhB solution, the photodegradation exhibited an exponential dependence on the exposure time followed by a sudden shutdown, but no complete photodegradation can be reached. Also, the residual quantity of RhB in solution after the photocatalytic reaction was determined by the initial RhB concentration. The photocatalytic degradation can be interpreted by the pseudo–first-order equation for the absorption of liquid/solid based on solid capacity; thus, photocatalytic degradation can be attributed to the interaction between the photoexcited electrons in the substrate and the antibonding orbital of the RhB in solution. The sudden shutdown was due to the inability of the photoexcited electrons in the substrate hopping to the antibonding orbital of RhB in the presence of the RhB intermediate products from the degraded RhB. In addition, this work showed that the photocatalytic reaction can be recovered after a thermal treatment of postreacted MoO₃ nanobelts, enhancing the utilization efficiency of the catalysis.     

La和Zn掺杂铌酸铋的光催化降解性能及其机理

用化学共沉淀法制备了镧和锌掺杂的铌酸铋纳米颗粒,表征了制备样品的微观结构和光催化降解性能。结果表明制备的样品对RhB表现出良好的可见光催化降解活性,且光催化效果受各种因素的影响。其中,Bi_0.96La_0.04NbO₄用量为0.15 g时,对pH=4、50 mL浓度为5 mg·L^-1 RhB溶液的光催化效果最佳。光催化机理研究表明催化剂在可见光照射下产生的电子空穴对RhB的降解起主要作用。该催化剂的制备方法简单、光催化性能稳定,5次循环后的活性仍大于95%。     

La和Zn掺杂铌酸铋的光催化降解性能及其机理

用化学共沉淀法制备了镧和锌掺杂的铌酸铋纳米颗粒,表征了制备样品的微观结构和光催化降解性能。结果表明制备的样品对RhB表现出良好的可见光催化降解活性,且光催化效果受各种因素的影响。其中,Bi_(0.96)La_(0.04)NbO_4用量为0.15 g时,对pH=4、50 m L浓度为5 mg·L-1 RhB溶液的光催化效果最佳。光催化机理研究表明催化剂在可见光照射下产生的电子空穴对Rh B的降解起主要作用。该催化剂的制备方法简单、光催化性能稳定,5次循环后的活性仍大于95%。     

Synthesis and Studies of the Visible‐Light Photocatalytic Properties of Near‐Monodisperse Bi‐Doped TiO2 Nanospheres

Near‐monodisperse Bi‐doped anatase TiO₂ nanospheres with almost uniform diameters in the range of 117 to 87 nm were prepared simply by introducing different amounts of bismuth nitrate pentahydrate into the reaction system and subsequent calcinations. X‐ray diffraction, UV‐visible diffuse reflectance spectra, and X‐ray photoelectron spectroscopy confirm that the doped ions substitute some of the lattice titanium atoms, and furthermore, Bi³⁺ and Bi⁴⁺ ions coexist. All the Bi‐doped TiO₂ samples show much better photocatalytic activity than pure TiO₂ in the degradation of rhodamine B (RhB) under the irradiation of visible light (λ>420 nm), and, interestingly, it was found that the degradation mechanism is different from the conventional one, which has already been reported elsewhere. The detailed mechanism is discussed in this article.