Dual Z-scheme heterojunction g-C3N4/Ag3PO4/AgBr photocatalyst with enhanced visible-light photocatalytic activity

Recently, there has been a significant interest in developing high-performance photocatalysts for removing organic pollutants from water environment. Herein, a ternary graphitic C₃N₄ (g-C₃N₄)/Ag₃PO₄/AgBr composite photocatalyst is synthesized using an in-situ precipitation-anion-exchange process and characterized by several spectroscopic and microscopic techniques. During the photocatalytic reaction, X-ray photoelectron spectroscopy clearly illustrated the formation of metallic Ag on the g-C₃N₄/Ag₃PO₄/AgBr composite surface. The ternary composite photocatalyst demonstrated an increased photoactivity under visible light (>420 nm), achieving a complete decolorization of methyl orange (MO) in 5 min. The ternary g-C₃N₄/Ag₃PO₄/AgBr hybrid was also applied to the 2-chlorophenol degradation under visible light, further confirming its excellent photocatalytic activity. In addition, quenching experiments revealed that holes (h⁺) and O₂^?– were the major attack species in the decolorization of MO. The enhanced photoactivity of g-C₃N₄/Ag₃PO₄/AgBr results from the efficient transfer/separation of photoinduced charges with the dual Z-scheme pathway and the charge recombination sites on the formed Ag particles.     

Ag3PO4 quantum dots loaded on the surface of leaf-like InVO4/BiVO4 heterojunction with enhanced photocatalytic activity

Leaf-like InVO₄/BiVO₄ nanoarchitectures with scale of 2 μm–5 μm were prepared by a facile hydrothermal method. Ag₃PO₄ quantum dots (QDs) were then deposited onto the surface of leaf-like InVO₄/BiVO₄ crystals via a simple deposition–precipitation technique. The photocatalytic tests displayed that the Ag₃PO₄/InVO₄/BiVO₄ nanocomposite possesses a much higher rate for degradation of rhodamine B (Rh B) than the sum of BiVO₄, InVO₄, Ag₃PO₄, Ag₃PO₄/InVO₄, Ag₃PO₄/BiVO₄ or InVO₄/BiVO₄ under visible light irradiation. The observed improvement in photocatalytic performance is associated with the extended absorption in the visible light region resulting from the Ag₃PO₄ QD loading, the high specific surface area, and the effective separation of photogenerated carriers at the Ag₃PO₄/InVO₄/BiVO₄ interfaces.     

NiTiO3/Ag3PO4 composites with improved photocatalytic activity under visible-light irradiation

A series of NiTiO₃/Ag₃PO₄ composites were prepared by a simple ion-exchange deposition method. The composition and morphology of the samples were determined by XRD, EDS and SEM. UV–vis DRS was used to characterize their optical absorption properties. The loading of NiTiO₃ could promote the efficient separation of photoinduced electron-hole pairs and enhance the charge carrier transport to improve the photocatalytic activity. The APO-5 composite exhibited the best photocatalytic activity for the degradation of methyl violet (MV). Kinetics studies indicated that the APO-5 composite showed an apparent rate constant of 0.115 min⁻¹, which was 2.61 times that of pure Ag₃PO₄.     

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.     

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.     

Synthesis of novel Cd2P2O7/Ag3PO4 photocatalyst with enhanced visible-light photocatalytic performance and the enhancement mechanism

Novel Cd₂P₂O₇/Ag₃PO₄ photocatalysts containing different mass fractions of Cd₂P₂O₇ were synthesized by a hydrothermal method. The photocatalysts were characterized by X-ray diffractometry, transmission electron microscopy, X-ray photoelectron spectroscopy, Electron spin resonance (ESR), Fourier transform infrared spectrometry, ultraviolet–visible absorption spectroscopy and photoluminescence spectroscopy. Photocatalytic activity was decided by the effective separation and low recombination rate of photogenerated electron-hole pairs. During the experiments, the Cd₂P₂O₇/Ag₃PO₄ composites possessed fierce electron- hole separation capacity. In particular, the 1 wt% Cd₂P₂O₇/Ag₃PO₄ catalyst displayed higher photocatalytic performance than pure Ag₃PO₄ under visible-light irradiation (λ>420 nm). The ESR spectrum showed the main active species during the methyl orange degradation were ·OH and ·O₂⁻.     

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.     

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.     

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.     

Increasing the photocatalytic and fungicide activities of Ag3PO4 microcrystals under visible-light irradiation

The present study reports for the first time the performance of silver phosphate (Ag₃PO₄) microcrystals as photocatalyst (degradation of Rodamine B-RhB) and antifungal agent (against Candida albicans–C. albicans) under visible-light irradiation (455 nm). Ag₃PO₄ microcrystals were synthesized by a simple co-precipitation (CP) method at room temperature. The structural and electronic properties of the as-synthetized Ag₃PO₄ have been investigated before and after 4 cycles of RhB degradation under visible light using X-ray diffraction (XRD), micro-Raman spectroscopy, UV–Vis spectrophotometer and field emission scanning electron microscopy (FE-SEM) images. The antifungal activity was analyzed in planktonic cells and 48h-biofilm of C. albicans by colony forming units (CFU) counting, confocal laser and FE-SE microscopies. Statistical analysis was carried out using SPSS software. Morphological and structural modifications of Ag₃PO₄ were observed upon recycling. After 4 recycles, the material maintained its photodegradation property; an eightfold increase in the efficiency of Ag₃PO₄ was observed in planktonic cells and a two fold increase in biofilm when irradiated under visible light. Thus, higher antifungal effectiveness against C. albicans was obtained when associated with visible-light irradiation.     

Simple fabrication of rod-like N-doped TiO2/Ag with enhanced visible-light photocatalytic activity

Rod-like N-doped TiO₂/Ag composites were successfully synthesized by a modified sol–gel method, without adding any surfactants. The entire preparation differs from the traditional sol–gel synthesis of TiO₂ that the reaction can get controlled by adjusting the flow speed of water vapor and NH₃. Characterization results show that as-prepared samples were uniform nanorods with an average length of ca. 3 µm and a cross section diameter of ca. 150 nm. The rod-like structure was formed during the annealing process. A possible mechanism was proposed to illustrate the formation of rod-like Ag–N–TiO₂. The degradation of methylene blue performed under visible light with the prepared nanorods as the photocatalyst demonstrated the photocatalytic activities of TiO₂ can be improved by the synergistic effect of N doping and Ag modification. In addition, as-prepared TiO₂-based photocatalyst exhibits a significantly enhanced photo-chemical stability after 5 catalytic cycles mainly due to the rod-like morphology. This indicated that they have some potential value in practical application.     

Enhanced photoresponse and photocatalytic activities of graphene quantum dots sensitized Ag/TiO2 thin film

TiO₂ thin films were fabricated through hydrothermal method. Silver nanoparticles were loaded on TiO₂ thin films via photoreduction technique. Subsequently, the graphene quantum dots (GQDs) were spin‐coated on the Ag/TiO₂ nanocomposites thin films. The crystal structure, surface morphology and UV‐vis absorbance were tested by XRD, SEM and ultraviolet‐visible spectrophotometer. These results indicated that Ag nanoparticles and GQDs are anchored on the TiO₂ nanorods. Absorbance of Ag/TiO₂ and GQDs/Ag/TiO₂ nanocomposite thin films have been extended into the visible region. Visible‐light response of the samples were investigated by electrochemical workstation. The photoresponse of the sample can be enhanced by sensitization of the Ag nanoparticles and GQDs. The enhanced visible‐light response may be due to the surface plasmon resonance of silver nanoparticles and visible absorbance of GQDs. The highest photocatalytic activity has been observed in the 9‐GQDs/Ag/TiO₂ composite thin film. The efficient charge separation and transportation can be achieved by introducing the Ag nanoparticles and GQDs in the TiO₂ thin film.     

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.     

Preparation and characterization of Ag3PO4/BiOI composites with enhanced visible light driven photocatalytic performance

Ag₃PO₄/BiOI composites were successfully prepared by a facial room temperature liquid phase method. Ag₃PO₄ nanoparticles were uniformly distributed on the surface of BiOI nanosheets. The photodegradation tests show that the photocatalytic efficiency was increased at first and then decreased when further increasing Ag₃PO₄ content in the composites. The best photocatalytic performance was obtained for the sample with Ag/Bi ratio of 0.3 and the photodegradation efficiency of Ag₃PO₄/BiOI was nearly 10 times that of BiOI. The enhanced photocatalytic activity of the composites was due to the improved photogenerated carrier separation capacity, being induced by the coupling effects of the two semiconductors.     

Porous Ag3PO4 microtubes with improved photocatalytic properties

The Ag₃PO₄ porous microtubes are, for the first time, prepared by a one-pot synthesis using polyethylene glycol 200 (PEG200) as the reaction medium. This study establishes that PEG 200 plays a vital role in the formation of the unique structures. Under visible light irradiation (≥ 420 nm), the porous sample exhibits a higher photocatalytic activity for the degradation of RhB than solid Ag₃PO₄ and Ag₃PO₄ tetrapods, which has been mainly ascribed to the novel hollow structure.     

Ag3PO4/Bi2WO6 hierarchical heterostructures with enhanced visible light photocatalytic activity for the degradation of phenol

The Ag₃PO₄/Bi₂WO₆ hierarchical heterostructures were prepared by a combination of hydrothermal technique and in situ precipitation method for the first time. The Ag₃PO₄/Bi₂WO₆ hierarchical heterostructures displayed enhanced visible-light photocatalytic activity against phenol. The enhanced photocatalytic activity could be attributed to the effective separation of photogenerated carriers driven by the photoinduced potential difference generated at the Ag₃PO₄/Bi₂WO₆ heterojunction interface. Repetitive tests showed that the Ag₃PO₄/Bi₂WO₆ hierarchical heterostructures maintained high catalytic activity over several cycles, and it had a better regeneration capability under mild conditions.     

WO3/C/Ag3PO4复合材料光催化降解双酚A

以磷酸法制备的活性炭、WO3、AgNO3、Na2HPO4?12H2O为原料,采用共沉淀法制备WO3与C不同含量的系列WO3/C/Ag3PO4复合材料.采用XRD、FTIR、XPS、SEM、TEM和固体紫外漫反射(UV-DRS)技术对其进行了结构表征.在可见光照射下,以双酚A(BPA)模拟污染物,评价WO3/C/Ag3P...     

WO3/C/Ag3PO4复合材料光催化降解双酚A

以磷酸法制备的活性炭、WO3、AgNO3、Na2HPO4为原料,采用共沉淀法制备WO3/C/Ag3PO4复合材料。采用X 射线衍射（XRD）、傅里叶红外光谱（FT-IR）、光电子能谱（XPS）、扫描电镜（SEM）、透射电镜（TEM）和固体紫外漫反射（UV-DRS）技术对其进行表征。结果表明,Ag3PO4与WO3之间形成异质结。在可见光照射下,以双酚A(BPA)模拟污染物,评价WO3/C/Ag3PO4复合材料的光催化降解性能,并提出 WO3/ C/Ag3PO4 复合材料对BPA的光降解机理。结果表明,在一系列光催化剂中, 23% WO3/ 7% C/ Ag3PO4 复合材料在可见光下对10 mg/L BPA水溶液的降解率在90 min分钟达到95%,明显高于单一的Ag3PO4和WO3。经过3次循环重复,BPA的降解率仍能保持在74%,表明WO3/C/Ag3PO4光催化剂具有良好的稳定性。光催化机理表明,自由基?O- 2和h 在降解过程中起主要作用。     

One step synthesis of Ag/Ag3PO4/BiPO4 double-heterostructured nanocomposites with enhanced visible-light photocatalytic activity and stability

Heterogeneous Ag/Ag₃PO₄/BiPO₄ photocatalyst was synthesized by a one-step low temperature chemical bath method and exhibited better photocatalytic activity and better stability than those of individual Ag₃PO₄ or BiPO₄ nanoparticles for photodegradation of organic compounds (Rhodamine B) in the absence of electron accepters under visible light (λ>420 nm). The enhanced photocatalytic performance is mainly ascribed to the strong visible-light absorption originating from high efficient separations of photogenerated electron–hole pairs through Ag₃PO₄/BiPO₄ and Ag/Ag₃PO₄ heterostructures.