Nanocomposite of CeVO4/BiVO4 Loaded on Reduced Graphene Oxide for the Photocatalytic Degradation of Methyl Orange

A facile procedure, involving one-pot synthesis of CeVO₄/BiVO₄ and in-situ reduction of graphene oxide (GO), has been used to prepare CeVO₄/BiVO₄/rGO nanocomposites. Different ratios of the CeVO₄–BiVO₄ were prepared to afford composites represented as CBVG3, CBVG5, and CBVG7. The ternary nanocomposite materials were characterized by using powder X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), photoluminescence and UV–vis spectroscopic techniques. Photocatalytic efficiency of the as-prepared ternary nanocomposites was investigated through the photo degradation of methyl orange under a visible light irradiation at 470 nm. The photocatalytic performance was enhanced by loading the CeVO₄/BiVO₄ nanoparticles on reduced graphene oxide (rGO), given MO degradation rate of 57, 65, 80, and 90% for BVG, CBVG3, CBVG5, and CBVG7, respectively after exposure to visible light for 120 min. Effects of experimental process parameters including initial dye concentration, catalysts loading and effect of different modification regimes were studied using CBVG7, which exhibited the highest efficiency. The improvement in the photocatalytic efficiency may be attributed to increased surface area of the nanocomposites, enhanced light absorption capacity and improved charge separation. The study showed a one-pot synthesis route to prepare promising CeVO₄/BiVO₄/GO nanocomposites for the photo-enhanced degradation of dye contaminants.

     

Rational design of ternary NiS/CQDs/ZnIn2S4 nanocomposites as efficient noble-metal-free photocatalyst for hydrogen evolution under visible light

The NiS/CQDs nanocomposite (CQDs represents carbon quantum dots), with a mass ratio of NiS/CQDs to be 1.19:1 based on the ICP result, was obtained via a facile hydrothermal method from a mixture of CQDs, Ni(OAc)₂ and Na₂S. The self-assembly of ZnIn₂S₄ microspheres on the surface of NiS/CQDs was realized under microwave conditions to obtain a ternary NiS/CQDs/ZnIn₂S₄ nanocomposite. The as-obtained NiS/CQDs/ZnIn₂S₄ nanocomposite was fully characterized, and its photocatalytic hydrogen evolution under visible light irradiation was investigated. The ternary NiS/CQDs/ZnIn₂S₄ nanocomposite showed superior photocatalytic activity for hydrogen evolution than ternary CQDs/NiS/ZnIn₂S₄, which was obtained by deposition of NiS in the preformed CQDs/ZnIn₂S₄. The superior photocatalytic performance of ternary NiS/CQDs/ZnIn₂S₄ is ascribed to the introduction of CQDs, which act as a bridge to promote the vectorial transfer of photo-generated electrons from ZnIn₂S₄ to NiS. This result suggests that the rational design and fabrication of ternary CQDs-based systems are important for the efficient photocatalytic hydrogen evolution. This study provides a strategy for developing highly efficient noble-metal-free photocatalysts for hydrogen evolution using CQDs as a bridge to promote the charge transfer in the nanocomposite.     

Bi2MoO6/BiVO4异质结的水热合成和可见光催化活性

采用一步水热法制备Bi₂MoO₆/BiVO₄复合光催化剂. 利用X 射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、高分辨透射电子显微镜(HRTEM)等手段对其晶体结构和微观结构进行了表征. 结果表明, Bi₂MoO₆纳米粒子沉积在BiVO₄纳米片表面从而形成异质结结构. 紫外-可见漫反射光谱(UV-Vis DRS)表明所制备的Bi₂MoO₆/BiVO₄异质结较纯相Bi₂MoO₆和BiVO₄对可见光吸收更强. 由于形成异质结结构及其光吸收性能使Bi₂MoO₆/BiVO₄ 光催化活性有较大提高. 可见光下(λ>420 nm)光催化降解罗丹明B (RhB)实验结果表明,Bi₂MoO₆/BiVO₄光催化活性较纯相Bi₂MoO₆和BiVO₄高. Bi₂MoO₆/BiVO₄样品光催化性能提高的原因是Bi₂MoO₆和BiVO₄形成异质结, 从而有效抑制光生电子-空穴对的复合, 增大了可见光吸收范围及比表面积.     

四角星形BiVO4/Bi2O3催化剂的制备及性能

采用水热法合成具有四角星形貌的钒酸铋,再将钒酸铋浸渍在碱溶液里二次水热,制备出BiVO_4/Bi_2O_3催化剂。采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM),紫外-可见漫反射(UV-Vis DRS)等方法对样品进行表征。可见光下,BiVO_4/Bi_2O_3复合物的光催化降解罗丹明B性能及光电流响应均优于纯BiVO_4。这是由于BiVO_4/Bi_2O_3复合材料形成了异质结构,有效抑制了光生电子与空穴的复合效率。     

四角星形BiVO4/Bi2O3催化剂的制备及性能研究

采用水热法合成具有四角星形貌的钒酸铋,再将钒酸铋浸渍在碱溶液里二次水热,制备出BiVO₄/Bi₂O₃催化剂。采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM),紫外-射(UV-Vis DRS)等方法征。可见光下,BiVO₄/Bi₂O₃复合物的光催化降解丹明B性能及光电优于纯BiVO₄。BiVO₄/Bi₂O₃复合材料形成了异质结构,有效抑制了光电子与空穴的复合效率。     

Comparison study of BiVO4 heterojunctions photocatalyst with different carbon materials

MWCNT/BiVO₄ and RGO/BiVO₄ heterojunctions were synthesized by the sol–gel method, and the photocatalytic activity of MWCNT/BiVO₄ and RGO/BiVO₄ were evaluated by monitoring the degradation of RhB in a heterogeneous photocatalytic reactor. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results indicated that a series of heterojunction structure composites were successfully synthesized, the heterojunction structure playing a crucial role in the electron–hole recombination. The crystal structure of BiVO₄ was still monoclinic after the doping of MWCNT and RGO according to the XRD analysis, while the active sites of MWCNT/BiVO₄ and RGO/BiVO₄ were more than pure BiVO₄. The RGO with a two-dimensional carbon sheet expressed higher performance than MWCNT with a one-dimensional carbon sheet for BiVO₄ because the layered structure of the RGO had a stronger electron-trapping capability than MWCNT. The optimal MWCNT content was 2%, and the 6% RGO/BiVO₄ showed the highest photocatalytic degradation efficiency of RhB. The photocatalytic degradation efficiency remained above 80% after five cycle tests.

     

Insights into photoluminescence property and photocatalytic activity of cubic and rhombohedral ZnIn2S4

Cubic and rhombohedral ZnIn₂S₄ were synthesized by thermal sulfidation of Zn-In mixed oxide precursor in H₂S atmosphere at different temperatures. Cubic ZnIn₂S₄ was obtained when Zn-In mixed oxide precursor was sulfurized at 400 °C. With sulfidation temperature increasing from 400 to 800 °C, the crystal phase of ZnIn₂S₄ gradually turned from cubic to rhombohedral, which was demonstrated by different analysis techniques such as XRD, Raman, SEM, etc. UV-vis absorption spectra indicated that cubic ZnIn₂S₄ displayed better light absorption property than rhombohedral ZnIn₂S₄, with band gaps calculated to be 2.0 and 2.5 eV, respectively. However, under visible light irradiation, rhombohedral ZnIn₂S₄ photocatalyzed H₂ evolution from aqueous sodium sulfite/sulfide solution efficiently, whereas cubic ZnIn₂S₄ was not active for this reaction. The photoluminescence property revealed the different dynamics of photogenerated carriers, which made a predominant contribution to the increasing photocatalytic performances of ZnIn₂S₄ with crystal phase turning from cubic to rhombohedral.     

Bi/BiVO4&Bi4V2O11复合催化剂的制备及其光催化性能

经由溶剂热反应、光辅助还原过程制备Bi/Bi VO_4Bi_4V_2O_(11)纳米复合光催化材料。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、高分辨率透射电子显微镜(HRTEM)、X射线光电子能谱(XPS)、紫外-可见漫反射光谱(UV-Vis DRS)、N_2吸附-脱附等温线和光致发光(PL)等手段对该复合物进行表征。实验结果表明当金属Bi与BiVO_4Bi_4V_2O_(11)的质量比值为0.8,可见光照射30 min时,Bi/BiVO_4Bi_4V_2O_(11)复合催化剂对罗丹明B(RhB)的降解率可达95.6%。此外,Bi/BiVO_4Bi_4V_2O_(11)对四环素(TC)的降解也表现出增强的光催化性能。Bi/BiVO_4Bi_4V_2O_(11)复合材料提升的光催化性能可能归因于金属Bi的表面等离子体共振(SPR)效应、拓宽的可见光吸收范围和增大的比表面积。此外,提出了复合光催化剂可能的光催化机理。     

Surface domain potential difference-mediated efficient charge separation on a defective ZnIn2S4 microsphere photocatalyst

Low-efficiency charge separation in metal sulfides is a major obstacle to realizing high photocatalytic performance. Herein, we propose the concept of a similar surface domain potential difference between adjacent microdomains with and without surface S vacancies on ZnIn₂S₄ to mediate charge separation. Defective ZnIn₂S₄ microspheres (DZISNPs) are prepared through a solvothermal method combined with a low-temperature hydrogenation surface engineering strategy. The as-prepared DZISNPs with a narrowed bandgap of 2.38 eV possess a large specific surface area of 178.5 m² g^?1, a pore size of 6.89 nm, and a pore volume of 0.36 cm³ g^?1, which further improves the visible light absorption. The resultant DZISNPs exhibit excellent visible light activity (2.15 mmol h^?1 g^?1), which is ～two-fold higher than that of the original DZISNP. The experimental results and DFT calculations reveal that the enhanced property can be a result of the surface S vacancy-induced surface domain potential difference, promoting the spatial separation of electrons and holes. Furthermore, the long-term stability of the DZISNPs indicates that the formation of surface S vacancies can inhibit the photocorrosion of ZnIn₂S₄. This strategy provides new insights for fabricating highly efficient and stable sulfide photocatalysts.     

Construction of Hierarchical Hollow Co9S8/ZnIn2S4 Tubular Heterostructures for Highly Efficient Solar Energy Conversion and Environmental Remediation

Visible‐light‐responsive hierarchical Co₉S₈/ZnIn₂S₄ tubular heterostructures are fabricated by growing 2D ZnIn₂S₄ nanosheets on 1D hollow Co₉S₈ nanotubes. This design combines two photoresponsive sulfide semiconductors in a stable heterojunction with a hierarchical hollow tubular structure, improving visible‐light absorption, yielding a large surface area, exposing sufficient catalytically active sites, and promoting the separation and migration of photogenerated charges. The hierarchical nanotubes exhibit excellent photocatalytic H₂ evolution and Cr^VI reduction efficiency. Under visible‐light illumination, the optimized Co₉S₈/ZnIn₂S₄ heterostructure provides a remarkable H₂ generation rate of 9039 μmol h^?1 g^?1 without the use of any co‐catalysts and Cr^VI is completely reduced in 45 min. The Co₉S₈/ZnIn₂S₄ heterostructure is stable after multiple photocatalytic cycles.     

One-pot synthesis of peony-like Bi2S3/BiVO4(040) with high photocatalytic activity for glyphosate degradation under visible light irradiation

In this work, samples consisting of BiVO₄ with exposed (040) facets coupled with Bi₂S₃ (Bi₂S₃/BiVO₄) were prepared through a one-pot hydrothermal method, using ethylenediaminetetraacetic acid as directing agent and L-cysteine as sulfur source and soft template. X-ray diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy measurements indicated that the Bi₂S₃ content had a significant influence on the growth of (040) and (121) facets as well as on the morphology of the Bi₂S₃/BiVO₄ samples. When the Bi₂S₃ content reached 1 mmol, the Bi₂S₃/BiVO₄ samples exhibited a peony-like morphology. The results of transient photocurrent tests and electrochemical impedance spectroscopy measurements confirmed that a more effective charge separation and a faster interfacial charge transfer occurred in Bi₂S₃/BiVO₄ than BiVO₄. The enhanced photocatalytic activity of the Bi₂S₃/BiVO₄ samples could be attributed to the improved absorption capability in the visible light region and the enhanced electron-hole pair separation efficiency due to the formation of the Bi₂S₃/BiVO₄ heterostructure. In addition, the Bi₂S₃/BiVO₄ samples showed relative stability and reusability. The simple method presented in this work could be used to fabricate composite photocatalysts with high activity for different applications, such as photocatalytic degradation of organic pollutants, photocatalytic splitting of water, and photocatalytic reduction of carbon dioxide.     

Synergic effect of Type II ZnO/BiVO4 magnetic heterostructures for visible light-driven degradation of bisphenol A and methyl violet

Construction of an effective heterojunction for unimpeded flow of photogenerated charges and their prolonged separation is imperative for environmental photocatalysis. Herein, we have designed an efficient magnetic ZnO/BiVO₄ type-II heterostructure, which was employed for proficient degradation of persistent methyl violet dye with an efficiency of 97.6% in 90 min and a hazardous organic pollutant, namely, bisphenol A. UV-DRS and photoluminescence studies demonstrated that the fabricated nanocomposite exhibited effective light absorption and prolonged charge separation, thereby resulting in high photocatalytic efficacy under visible light irradiation. The efficacy of developed magnetic ZnO/BiVO₄ was also compared with pristine BiVO₄ and undoped magnetic ZnO, which indicated that the constructed heterostructure displayed approximately threefold and sixfold activity in contrast with bare BiVO₄ and undoped magnetic ZnO nanoparticles, respectively. Radical trapping studies, ESR analysis along with GC-MS analysis were conducted to elucidate the mechanistic pathway during the photodegradation process. This work provides a rational technical approach and research ideas for photocatalytic degradation of harmful organic pollutants in an environment-friendly manner by employing energy-efficient LEDs. Besides, good recyclability of catalyst makes it a promising candidate for large-scale applications.     

TiO2/BiVO4, a Heterojuncted Microfiber with Enhanced Photocatalytic Performance for Methylene Blue under Visible Light Irradiation

Novel TiO₂/BiVO₄ microfiber heterojunctions were constructed using cotton as biomorphic templates. The as-synthesized samples were characterized by scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectra and photocatalytic experiment. The morphology of the as-synthesized TiO₂/BiVO₄ composites was consisted of a large quantity of microfiber structures with diameter from 2.5 μm to 5 μm, and the surface of samples became more coarse and compact with the increase of weight ratio of TiO₂. The TiO₂/BiVO₄ samples with proper content (10.00wt%) showed the highest pho-tocatalytic degradation activity for methylene blue (MB) degradation among all the samples under visible light, and 88.58%MB could be degraded within 150 min. The enhancement of photocatalytic activity was mainly attributed to the formation of n-n heterojunction at the contact interface of TiO₂ and BiVO₄, which not only narrowed the band gap of BiVO₄ for extending the absorption range of visible light, but also promoted the transfer of charge carriers across interface. A possible photodegradation mechanism of MB in the presence of TiO₂/BiVO₄ microfibrous photocatalyst was proposed.     

Enhanced visible-light photocatalytic activities of porous olive-shaped sulfur-doped BiVO4-supported cobalt oxides

Porous S-doped bismuth vanadate with an olive-like morphology and its supported cobalt oxide (y wt% CoO_x/BiVO_4−δS_0.08, y = 0.1, 0.8, and 1.6) photocatalysts were fabricated using the dodecylamine-assisted alcohol-hydrothermal and incipient wetness impregnation methods, respectively. It is shown that the y wt% CoO_x/BiVO_4−δS_0.08 photocatalysts were single-phase with a monoclinic scheetlite structure, a porous olive-like morphology, a surface area of 8.8–9.2 m²/g, and a bandgap energy of 2.38–2.41 eV. There was the co-presence of surface Bi⁵⁺, Bi³⁺, V⁵⁺, V³⁺, Co³⁺, and Co²⁺ species in y wt% CoO_x/BiVO_4−δS_0.08. The 0.8 wt% CoO_x/BiVO_4−δS_0.08 sample performed the best for methylene blue degradation under visible-light illumination. The photocatalytic mechanism was also discussed. We believe that the sulfur and CoO_x co-doping, higher oxygen adspecies concentration, and lower bandgap energy were responsible for the excellent visible-light-driven catalytic activity of 0.8 wt% CoO_x/BiVO_4−δS_0.08.     

硫掺杂橄榄状BiVO4上可见光降解亚甲基蓝和甲醛水溶液性能

在无和有S源(Na₂S或硫脲)存在的条件下,采用十二胺辅助的醇-水热法制备了多孔单斜晶相结构的BiVO_4-δ和不同含量S掺杂的BiVO_4-δ光催化剂.利用多种手段表征了催化材料的物化性质,评价了它们在可见光照射下催化降解亚甲基蓝或甲醛的反应活性.结果表明,所制光催化剂为单斜白钨矿晶相结构,具有多孔橄榄状形貌,比表面积为8.4-12.5m²/g,带隙能为2.40-2.48eV.在S掺杂BiVO_4-δ表面同时含有Bi⁵⁺,Bi⁴⁺,V⁵⁺和V⁴⁺物种.S掺杂对BiVO_4-δ光催化剂的活性影响很大.在可见光下照射下,BiVO_4-δS_0.08光催化剂对亚甲基蓝和甲醛降解反应显示出最高的光催化活性,这与其较高的表面氧物种浓度和较低的带隙能相关.     

Facile preparation of BiVO4 thin film by screen-printing technique for its photocatalytic performance in the degradation of tetracycline under simulated sunlight irradiation

BiVO₄ films were prepared by a screen-printing technique on Corning glass substrate. The material employed to prepare the films was synthetized by the hydrothermal method. For comparative purposes, the BiVO₄ was synthesized via solid state reaction and deposited in film form by the same technique. From the X-ray diffraction structural characterization it has been stated that BiVO₄ films crystallized in the monoclinic structure. The characterization of BiVO₄ films was complemented with scanning electron microscopy, which revealed a morphology of irregular form and dendritic type depending on the starting material. The thickness of the BiVO₄ films were determined by profilometry. The film obtained from the hydrothermal method showed minor photoluminescence, i.e., the sample showed low recombination of electron–hole pairs. The highest photocatalytic activity in the degradation of tetracycline (TC) was presented for the BiVO₄ films obtained from hydrothermal powders under simulated sunlight irradiation; attributed mainly to the surface area value, smaller particle size and lower recombination of electron–hole pairs. Mineralization degree of TC by BiVO₄ films was determined by the total organic carbon analysis, reaching 50% after 24 h of irradiation. The main oxidizing species that was most influenced in the degradation of TC was the hydroxyl radical (OH^·).

     

Co掺杂提高ZnIn2S4光催化剂可见光下的产氢性能

采用溶剂热法制备出Co掺杂的ZnIn₂S₄催化剂.用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)漫反射光谱等技术对其进行了表征. XRD 和XPS结果表明, Co成功地掺杂到ZnIn₂S₄晶格内. 随着Co掺杂量增加, 样品的吸收边发生红移, 同时ZnIn₂S₄的微球形态会遭到破坏. 光催化反应实验结果表明Co²⁺掺杂提高了ZnIn₂S₄光催化性能, 掺杂量为0.3%(w)时表现出最佳催化性能. 并对可能的催化机理进行了讨论.     

中空管状g-C3N4/Ag3PO4复合催化剂的制备及其可见光催化性能

用化学沉淀法制备中空管状g-C₃N₄/Ag₃PO₄复合催化剂。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外可见漫反射光谱(UV-Vis DRS)和荧光光谱对其结构、形貌和光学性能进行了表征。结果表明：Ag₃PO₄纳米颗粒均匀地分散在中空管状g-C₃N₄表面,两者紧密结合形成异质结。研究复合催化剂在可见光照射下降解盐酸四环素(TC)的光催化活性。结果显示：复合催化剂在80 min内对TC的降解率为98%,其降解反应速率常数是纯相Ag₃PO₄的3倍。经过5次循环实验后复合催化剂对于TC的降解率仍保持87%,具有优良的循环稳定性。捕获实验表明空穴(h⁺)和超氧负离子(·O^-₂)是光催化反应过程中的主要活性物种。根据能带理论,提出了复合催化剂异质结的Z型光催化机理。     

Visible light photocatalytic activity of BiVO4 particles with different morphologies

Bismuth vanadate (BiVO₄) particles with different morphologies were synthesized by a one-step hydrothermal process and their optical and photocatalytic properties were investigated. Their crystal structure and microstructures were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). XRD patterns demonstrate that the as-prepared samples are monoclinic cell. FESEM shows that BiVO₄ crystals can be fabricated in different morphologies by simply manipulating the reaction parameters of hydrothermal process. The UV–visible diffuse reflectance spectra (UV–vis DRS) reveal that the band gaps of BiVO₄ photocatalysts are about 2.07–2.21 eV. The as-prepared BiVO₄ photocatalysts exhibit higher photocatalytic activities in the degradation of rhodamine B (Rh B) under visible light irradiation (λ > 420 nm) compared with traditional N-doped TiO₂ (N-TiO₂). Furthermore, wheat like BiVO₄ sample reveals the highest photocatalytic activity. Up to 100% Rh B is decolorized after visible light irradiation for 180 min. The reason for the difference in the photocatalytic activities for BiVO₄ samples obtained at different conditions were systematically studied based on their shape, size and the variation of local structure.     

Bi2Fe4O9/g-C3N4/UiO-66三元复合材料的协同光催化作用

通过水热法合成具有协同机制的三元复合材料Bi₂Fe₄O₉/g-C₃N₄/UiO-66,研究表明三元复合光催化剂的催化活性要高于二元材料和纯材料。这主要是由于Bi₂Fe₄O₉更易于和g-C₃N₄结合形成稳定的Z-scheme异质结结构,使三元复合材料增强了可见光响应能力,提高了电子-空穴分离能力,增强了空穴和电子的氧化还原能力。