Photosensitization of Fe3O4/ZnO by AgBr and Ag3PO4 to fabricate novel magnetically recoverable nanocomposites with significantly enhanced photocatalytic activity under visible-light irradiation

In this paper, novel quaternary Fe₃O₄/ZnO/AgBr/Ag₃PO₄ nanocomposites with different weight percents of Ag₃PO₄ were successfully prepared through refluxing method at 96 °C. The as-prepared products were characterized with XRD, EDX, SEM, TEM, UV-vis DRS, FT-IR, PL, and VSM techniques to determine their phase structure, purity, morphology, spectroscopic, and magnetic properties. Photocatalytic degradation of rhodamine B under visible-light irradiation indicated that the nanocomposite with 20% of Ag₃PO₄ has the best activity. Photocatalytic activity of this nanocomposite is nearly 68, 5.0, and 3.4-folds greater than those of the Fe₃O₄/ZnO, Fe₃O₄/ZnO/AgBr, and Fe₃O₄/ZnO/Ag₃PO₄ samples in degradation of rhodamine B, whereas 17, 6.7, and 2.8-folds greater in degradation of methylene blue, respectively. The activity enhancement was mainly ascribed to the enhanced visible-light absorption ability and formation of tandem n-n heterojunctions between counterparts of the nanocomposites, which facilitate the generation and separation of charge carriers. An additional advantage of these photocatalysts is magnetic recoverability using external magnetic field. In addition, using different scavengers, superoxide ion radicals were identified as the main oxidative species in the degradation reaction of rhodamine B. Finally, photocatalytic stability of the nanocomposite was evaluated for six cycles.     

Z-scheme AgSCN/Ag3PO4/C3N4 heterojunction with excellent photocatalytic degradation of ibuprofen

To develop a novel photocatalyst with high catalytic performance under sunlight, AgSCN/Ag₃PO₄/C₃N₄ heterojunction photocatalyst with Z-mechanism has been prepared, which demonstrates excellent photocatalytic performance for ibuprofen degradation. The catalytic activity of AgSCN/Ag₃PO₄/C₃N₄ is 1.5 and 3.3 times that of AgSCN/Ag₃PO₄ and Ag₃PO₄, respectively. The cyclic degradation number of AgSCN/Ag₃PO₄/C₃N₄ increases to seven because of the protection of AgSCN and C₃N₄ to Ag₃PO₄. The excellent photocatalytic performance of the AgSCN/Ag₃PO₄/C₃N₄ is attributed from the Z-mechanism with efficient separation efficiency of electron hole pair.     

Ag/g-C3N4 photocatalysts: Microwave-assisted synthesis and enhanced visible-light photocatalytic activity

Ag/g-C₃N₄ photocatalysts were synthesized by a rapid microwave-assisted polyol process. The characterization results showed monodisperse Ag nanoparticles with diameters of a few nanometers closely attached to the edges of g-C₃N₄. The presence of Ag nanoparticles in Ag/g-C₃N₄ photocatalysts enhanced the visible-light absorption and suppressed the recombination of photogenerated electron/hole pairs. The Ag/g-C₃N₄ photocatalysts exhibited the superior visible-light responsive photocatalytic activity for rhodamine B degradation. The mechanism of visible-light induced photocatalysis over Ag/g-C₃N₄ photocatalysts was also discussed.     

有机酸介导合成WO3/g-C3N4及其光催化性能

采用水热法制备了WO3/g-C3N4复合物,并探讨了草酸、柠檬酸、乙酸和水杨酸对复合物结构、形貌及催化活性的影响。结果表明,复合物中棒状WO3分布在片层状的g-C3N4上,二者结合紧密形成异质结构。以1 mol/L草酸为介导剂制备的WO3/g-C3N4的光催化活性最佳,当WO3和g-C3N4质量比为1∶1时,可见光下反应210 min,对罗丹明B的降解率达97.46%。自由基捕获实验表明,光催化反应活性基团排序为·O2->h+>·OH。经推测,光催化降解机制符合Z型机制。     

Construction of g-C3N4 nanotube/Ag3PO4 S-scheme heterojunction for enhanced photocatalytic oxygen generation

Heterojunction engineering is considered as a hopeful approach to ameliorate the separation of photogenerated carriers of photocatalysts, realizing efficient water-splitting performance. In this study, an organic-inorganic S-scheme of a one-dimensional g-C₃N₄ nanotube (TCN)/Ag₃PO₄ photocatalytic system with high photocatalytic water oxidation activity was designed by coupling g-C₃N₄ nanotubes over Ag₃PO₄ particles through a chemical coprecipitation method. The TCN/Ag₃PO₄ heterojunction demonstrated excellent photocatalytic O₂ production with an O₂ evolution rate of up to 370.2 μmol·L^?1·h^?1. X-ray photoelectron spectroscopy analysis showed that electron migration between TCN and Ag₃PO₄ led to the formation of an internal electric field pointing from TCN to Ag₃PO₄, which drove the S-scheme charge transfer mode between TCN and Ag₃PO₄. Accordingly, the TCN/Ag₃PO₄ heterojunction possessed fast charge separation and high redox ability, leading to high photoactivity and photostability. This research provides a new strategy for fabricating highly efficient inorganic-organic S-scheme photocatalysts for O₂ production.     

Efficient photocatalytic hydrogen production using an NH4TiOF3/TiO2/g-C3N4 composite with a 3D camellia-like Z-scheme heterojunction structure

Photocatalysis is one of the most promising ways to realize artificial photosynthesis. The biologically inspired photocatalysts with 3D flower-like structures have attracted much attention. In this study, an effective method for the synthesis of composite photocatalytic material, NH₄TiOF₃/TiO₂/g-C₃N₄, with a 3D camellia-like structure, was developed. The 3D hierarchical structure of the composite material enabled multiple refractions and reflections of light within the catalyst, which greatly improved the efficiency of the sunlight harvesting. The combination of NH₄TiOF₃ and TiO₂ also effectively reduced the electron-hole recombination in the g-C₃N₄. To evaluate its photocatalytic performance, the prepared nanostructured composite materials were tested for the water-splitting with simulated sunlight. It showed the hydrogen evolution at the rate of 3.6 mmol/g/h, which is 4.0 times faster than that from the pure g-C₃N₄. The composite materials exhibited excellent cycling stability. The detailed mechanism of the Z-scheme heterojunction was also discussed. The proposed synthesis route for the creation of 3D flower-like hierarchical composites provides a new effective technique for developing efficient, active, and stable composite photocatalysts for hydrogen production.     

S-scheme g-C3N4/TiO2/CFs heterojunction composites with multi-dimensional through-holes and enhanced visible-light photocatalytic activity

A novel multi-dimensional through-holes structure of g-C₃N₄ with adjustable pore size was prepared by controlling the mass ratio of oxamide (OA, structure guiding agent) to urea during one-step calcination process, and a break-rearrangement mechanism was explored. Then, a series of porous g-C₃N₄/TiO₂ (CT) composites with uniformly deposited TiO₂ nanoparticles were prepared based on the multi-dimensional framework by a facile hydrothermal method. The results show that a new S-scheme heterojunction with multi-dimensional through-channel structure was obtained, which is particularly desired for enhancing the visible-light utilization, reducing the carrier recombination rate and enhancing redox capacity. The CT composite obtained at hydrothermal treatment time of 2 h has a specific surface area of 180.15 m² g^-1, which shows high degradation capability (99.99%) for tetracycline hydrochloride (TC·HCl) under 350 W Xe lamp irradiation for 90 min. In addition, CT nanostructures was in-situ growth on carbon fiber (CFs), the degradation rate constant is 0.1566 min^-1, and 90% of the degradation efficiency can be maintained even after 5 consecutive cycles. It is expected to provide an effective reference for solving the problems of recovery difficulty and low reuse rate of powder photocatalytic materials.     

Construction of g-C3N4/TiO2/Ag composites with enhanced visible-light photocatalytic activity and antibacterial properties

In this study, the multifunctional carbon nitride based composite graphitic-C₃N₄ (g-C₃N₄)/TiO₂/Ag was prepared through a simple and efficient vacuum freeze-drying route. TiO₂ and Ag nanoparticles were demonstrated to decorate onto the surface of g-C₃N₄ sheet. In the ultraviolet–visible absorption test, a narrower band gap and red-shift of light absorption edge were observed for g-C₃N₄/TiO₂/Ag compared to pristine g-C₃N₄ and single-component modified g-C₃N₄/TiO₂. The photodegradation property of g-C₃N₄/TiO₂/Ag was investigated toward the degradation of methylene blue (abbreviated as MB) under the irradiation of visible light. These results indicated that the degradation performance of organic dyes for g-C₃N₄/TiO₂/Ag was obviously improved compared with g-C₃N₄/TiO₂ and g-C₃N₄. The reaction rate constant of MB degradation for g-C₃N₄/TiO₂/Ag was 4.24 times higher than that of pristine g-C₃N₄. In addition, such rationally constructed nanocomposite presented evidently enhanced antibacterial performance against the Gram-negative Escherichia coli. Concentration dependent antibacterial performance was systematically investigated. And 84% bacterial cell viability loss had been observed at 500 μg/mL g-C₃N₄/TiO₂/Ag within 2 h visible light irradiation.     

Z型Ag2CO3/BiOCl异质结光催化剂的制备及其可见光催化机理分析

通过溶剂热法制备BiOCl纳米片,共沉淀法制备Ag2 CO3和复合催化剂Ag2 CO3/BiOCl,研究各材料可见光催化降解罗丹明B的效果,确定Ag2 CO3与BiOCl的最佳配比,并通过表征分析复合材料的结构和异质结光催化降解机理.结果表明,当Ag2 CO3与BiOCl的质量比为50％时,Ag2 CO3/BiOCl异...     

Low-temperature synthesis one-dimensional Ag2CO3/SnFe2O4 Z-scheme with excellent visible-light photoactivity

In this study, Ag₂CO₃/SnFe₂O₄ (Ag₂CO₃/SFO) photocatalyst was prepared by a simple hydrothermal-ultrasonic method for the efficient degradation of ciprofloxacin and phenol. The SFO nanoparticles were attached on the surface of Ag₂CO₃ rods synthesized by a low-temperature precipitation method, resulting a unique 1D/0D morphology, which increased the number of active sites. Due to introduction of magnetic SFO, Ag₂CO₃/SFO exhibited excellent magnetic recovery performance. When the mass fraction of SFO was 5%, the degradation efficiency of composite photocatalyst was the highest, the degradation rate for ciprofloxacin was 6.5 and 1.5 times higher than pure SFO and Ag₂CO₃, respectively. The improved photoactivity of Ag₂CO₃/SFO should be attributed to the construction of heterojunction with tight interface, which boosts the separation and transfer of photoinduced electron and hole pairs. On the basis of experimental results, a possible Z-scheme photocatalytic mechanism was discussed. Additionally, the excellent photostability of Ag₂CO₃/SFO was proved by a cycle experiment.     

A g-C3N4 supported graphene oxide/Ag3PO4 composite with remarkably enhanced photocatalytic activity under visible light

In this work, a ternary composite photocatalyst of graphitic carbon nitride (g-C₃N₄), graphene oxide (GO), and Ag₃PO₄ was prepared through a simple precipitation route, in which Ag₃PO₄ nanoparticles covered or wrapped with GO sheets are supported on g-C₃N₄ sheets. The composite photocatalyst displays enhanced absorption in the visible region, and exhibited superior photocatalytic activity compared with single-component or binary composite photocatalysts in the photocatalytic decomposition of Rhodamine B. The enhancement of photocatalytic activity could be attributed to the synergistic effect among them. The ternary composite also exhibited enhanced stability, but further efforts should be made to make it more stable.     

A simple method to prepare g-C3N4/Ag-polypyrrole composites with enhanced visible-light photocatalytic activity

g-C₃N₄/Ag-polypyrrole (PPy) visible-light photocatalysts were prepared in a simple way, in which g-C₃N₄ was decorated with Ag nanoparticles, and covered by PPy layer. Their photoactivity was evaluated by degradation of rhodamine B. Compared with g-C₃N₄, g-C₃N₄/Ag and g-C₃N₄/PPy, the enhanced photocatalytic activity was obtained and explained according to the improvement of visible-light absorption and reduction of recombination between photogenerated electron-hole pairs with the help of Ag nanoparticles and PPy. Their reusability was evaluated by recycling experiments. The structures and chemical compositions before and after photocatalytic degradation were compared. Moreover, a possible photocatalytic mechanism was discussed in detail.     

Ag3PO4 quantum dots sensitized AgVO3 nanowires: A novel Ag3PO4/AgVO3 nanojunction with enhanced visible-light photocatalytic activity

Ag₃PO₄/AgVO₃ heterojunctions with high photocatalytic activities were synthesized via a simple and practical low-temperature solution-phase route by using AgVO₃ nanowires as substrate materials. The as-prepared Ag₃PO₄/AgVO₃ heterojunctions included Ag₃PO₄ quantum dots assembling uniformly on the surface of AgVO₃ nanowires. Compared with pure AgVO₃ nanowires, Ag₃PO₄/AgVO₃ composite photocatalysts exhibited enhanced photocatalytic activities under visible light irradiation in the decomposition of 4-chlorophenol (4-CP) ethanol solution. The enhanced performance is believed to be induced by the high specific surface area, strong visible-light absorption originating from the quantum dot sensitization of Ag₃PO₄, and high efficient separation of photogenerated electron–hole pairs through Ag₃PO₄/AgVO₃ heterojunction.     

Constructing 0D/1D/2D Z-scheme heterojunctions of Ag nanodots/SiC nanofibers/g-C3N4 nanosheets for efficient photocatalytic water splitting

Efficiently constructing nanostructured Z-scheme heterojunctions with good interface contact is a desired route to optimize the photocatalytic property of the materials. In this work, novel 0D/1D/2D Z-scheme silver/silicon carbide/graphitic carbon nitride (Ag/SiC/CN) photocatalysts were prepared from Ag nanodots loaded on SiC nanofibers/CN nanosheets (SiC/CN) composite, using the calcination and chemical reduction routes. The Ag/SiC/CN composite with an optimal 3% Ag loading dose performs the best H₂ evolution rate of 2971 μmol g^?1 h^?1, which is approximately 8.8, 1.5 and 4.5 times compared to CN, SiC/CN and 3% Ag/CN, respectively. Besides the Ag/SiC/CN composite presents a high apparent quantum efficiency (7.3%) and outstanding photo-corrosion resistance stability. The Ag nanodots are served as efficient carriers transfer center and cocatalyst to construct Z-scheme heterojunction interface, which can help to generate more photo-generated carries, shorten the electron transmission distance and increase the electron transfer rate, certifying that 0D/1D/2D Z-scheme photocatalytic system is high-efficiency and has great advantages in photocatalytic applications.     

A novel photocatalyst AgBr/ZnO/RGO with high visible light photocatalytic activity

A novel ternary photocatalyst AgBr/ZnO/RGO, where AgBr/ZnO is supported on reduced graphene oxide, is synthesized via a facile hydrothermal–impregnation method. The resultant composite presents a lamellar structure with AgBr nanoparticles homogeneously dispersing on the surface. The photocatalytic experiment for methyl orange dye degradation under visible light irradiation shows that ternary composite AgBr/ZnO/RGO has an activity 12.8 times and 2.3 times higher than binary photocatalysts ZnO/RGO and AgBr/ZnO respectively. More importantly, the ternary composite also demonstrates a good photostability. Metallic Ag is produced during the photocatalytic process, which may serve as the electron transfer mediator in the vectorial Z-scheme transfer of photogenerated charge carriers at the interface of AgBr/ZnO/RGO. The effective separation of photogenerated electrons and holes was proposed to be responsible for the enhancement of visible light photoactivity.     

Novel magnetically separable g-C3N4/AgBr/Fe3O4 nanocomposites as visible-light-driven photocatalysts with highly enhanced activities

In this study, we report novel magnetically separable g-C₃N₄/AgBr/Fe₃O₄ nanocomposites as visible-light-driven photocatalysts. The preparation method was simple, large-scale, and low-temperature and did not require any additives or post preparation treatments. The nanocomposites were characterized using X-ray diffraction, transmission electron microscopy, energy dispersive analysis of X-rays, UV–vis diffuse reflectance spectroscopy, Fourier transform-infrared spectroscopy, thermogravimetric analysis, and vibrating sample magnetometry techniques. Photocatalytic activity of the nanocomposites was investigated by degradation of rhodamine B under visible-light irradiation. The nanocomposite with 4:1 weight ratio of g-C₃N₄/AgBr to Fe₃O₄ exhibited superior activity in the degradation reaction. Activity of this nanocomposite was about 5.3 and 5-fold higher than those of g-C₃N₄, and g-C₃N₄/Fe₃O₄, respectively. Moreover, we investigated the influence of refluxing time, calcination temperature, and scavengers of reactive species on the degradation activity. Finally, the photocatalyst was magnetically separated, with high efficiency, from the treated solution after five successive cycles.