Visible-light-driven Research Articles

Superior photocatalytic performance of mechanosynthesized Bi2O3–Bi2WO6 nanocomposite in wastewater treatment

The heterostructured Bi2O3–Bi2WO6 nanocomposites with superior photocatalytic performance have been synthesized by the mechanical alloying method. Both nanosheet and nanoflower-like morphologies are obtained after different durations of milling. The semiconductor-semiconductor (S–S) heterojunction formation with the NHE (normal hydrogen electrode) scale is revealed from the band positions of Bi2O3 and Bi2WO6. Detailed microstructures of all nanocomposites have been characterized by the Rietveld refinement of XRD patterns and analyzing TEM images.The morphological hierarchy and changes of all samples have been disclosed in FESEM images. The bandgap value and the visible-light-driven (VLD) photocatalytic activity of all samples have been measured from the UV–vis absorbance spectra. The Rhodamine B (RhB) dye degradation performance of the photocatalyst, its reusability, and active radical species involved in the photocatalytic reaction in all nanocomposites are obtained by analyzing UV–vis absorbance spectra.The EDX elemental mapping reveals the stability of the photocatalyst. The photocatalytic performance of all milled samples has been investigated through the degradation of RhB dye in an aqueous solution under solar light in the presence. A significant amount (~87%) of RhB degradation within 240 min has been achieved with the 5h milled Bi2O3-WO3 nanocomposite.

Facile synthesis of BiOCl/g-C3N4 heterojunction via in situ hydrolysis of Bi nanospheres: a high-efficiency visible-light-driven photocatalyst

BiOCl/g-C3N4 (BC) heterojunctions were constructed successfully through a novel in situ hydrolysis method by taking metallic Bi nanospheres as Bi source. The TEM and HRTEM images showed the heterogeneous nanostructures at the interface between BiOCl and g-C3N4. The combination of BiOCl and g-C3N4 enlarged the light adsorption range of the BC heterojunctions, which extended to visible region. Besides, the contact of the two semiconductors at the heterointerfaces improved the separation efficiency of photoinduced charge carriers, thus endowing the BC samples with superior visible-light-driven (VLD) photocatalytic performance in degrading organic pollutants. Notably, the BC12% sample exhibited the optimized photocatalytic activity in which 97.3% of RhB was decomposed within 30 min, achieving 13.87- and 4.26-times improvement than the bare BiOCl and pristine g-C3N4, respectively. Moreover, the trapping experiments revealed that .O2− and h+ were the dominant active species during the degradation processes of RhB. Meanwhile, the possible degradation pathway of RhB was proposed on the basis of the intermediate products detected by LC–MS, and the appearance photocatalytic mechanisms were also discussed in detail. As an original strategy to obtain samples with highly dispersed heterointerface, this work provides a facile route for the surface modification of g-C3N4 via a facile hydrolysis process of metallic particles to form heterostructures and very promising for practical application.

Construction of multifunctional dual Z-scheme composites with enhanced photocatalytic activities for degradation of ciprofloxacin

Visible-light-driven (VLD) photocatalysis has aroused extensive attention due to their great potential in applications concerning energy crisis and environmental pollution. Hence, for the first time, VLD and magnetic recyclable dual Z-scheme NiFe2O4/Bi2WO6/AgI (NBA) composites were prepared via a hydrothermal method to obtain NiFe2O4/Bi2WO6 (NB) following an in situ deposition of AgI. The as-prepared NBA catalysts exhibit excellent photocatalytic performance for the degradation of ciprofloxacin (CIP) compared to the pristine NiFe2O4, Bi2WO6 or AgI under visible-light (VL) illumination. Among them, the 75%NiFe2O4/Bi2WO6/AgI (75NBA) composite exhibits optimal photocatalytic efficiency, which is 1.67, 1.51, 1.83 times higher than those of the pristine NiFe2O4, Bi2WO6 and AgI within 60 min, respectively. The high catalytic efficiency may be ascribed to the synergistic effect of the increased VL harvesting and dual Z-Scheme transmission paths in 75NBA system. Furthermore, trapping experiments and electrochemical impedance spectroscopy (ESR) analysis verify the co-existing of OH and O2− in the 75NBA photocatalytic system. Additionally, the magnetic 75NBA can be rapidly separated from water by an external magnet. Based on the results from High performance liquid chromatography-mass spectrometry (HPLC-MS) analysis, four path ways towards the degradation of CIP are proposed. The highly efficient photocatalytic activity and magnetically reproducibility suggest that it is expected to be used in antibiotic wastewater treatment.

The controlled synthesis of g-C3N4/Cd-doped ZnO nanocomposites as potential photocatalysts for the disinfection and degradation of organic pollutants under visible light irradiation.

The in situ growth of well-dispersed Cd-doped ZnO nanoparticles (Cd-ZnO NPs) on graphitic carbon nitride (g-C3N4) nanosheets was successfully achieved through the co-precipitation method for the formation of Cd-doped ZnO nanocomposites with g-C3N4 (Cd-ZnO/g-C3N4 NCs). The effect of different compositions of ternary nanocomposites (Cd-ZnO/g-C3N4 NCs) on photocatalytic properties was investigated. Ternary NCs, in which 60% g-C3N4 hybridized with 7% Cd-doped ZnO (g-C3N4/Cd-ZnO) NCs were proven to be optimum visible-light-driven (VLD) photocatalysts for the degradation of methylene blue (MB) dye. The enhanced photodegradation of MB is mainly due to the increase in the generation of photogenerated charge carriers (reactive oxygen species (ROS), O2−, and ˙OH radicals). The electron spin resonance (ESR) experiment revealed that the superoxide and hydroxyl radicals were the leading species responsible for the degradation of MB. Moreover, the NC exhibited tremendous stability with a consistently high MB degradation rate for 10 successive catalytic cycles. The structural and optical properties of CdO, ZnO NPs, Cd-ZnO NPs, g-C3N4 NSs, and g-C3N4/Cd-ZnO NCs were investigated via XRD, SEM, EDX, TEM, FTIR spectroscopy, UV-Vis spectroscopy, ESR spectroscopy, and PL spectroscopy techniques. The synthesized photocatalysts were also applied against Gram-positive and Gram-negative bacterial strains to evaluate their antibacterial activities.

Facile synthesis of magnetic Fe@Al-ZnO nanocomposite for photocatalytic bacterial inactivation under visible-light irradiation

Magnetic Fe@Al-ZnO nanocomposite was systhesized through a facile two-step precipitation process for the first time, and employed as a highly active photocatalyst for visible-light-driven (VLD) inactivation of Escherichia coli. The as-synthesized nanocomposite was analyzed using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscope (SEM), vibrating sample magnetometer (VSM), X-ray photoelectron spectroscopy (XPS), UV–vis diffused reflectance spectra (UV–vis DRS) and photoluminescence (PL) spectra. The Fe@Al-ZnO photocatalysts displayed typical ferromagnetic property with the saturation magnetization of 35.2 emu/g, which predominantly facilitated magnetic separation and recycling in applications. The photocatalyst dosage was found to have a significant influence on the VLD photocatalytic bacterial inactivation activity of Fe@Al-ZnO. Under visible-light irradiation, 40 mg of Fe@Al-ZnO could entirely inactivate 7-log of bacterial cells in 5 h. Notably, the phase structure and magnetic property of the nanocomposite after photocatalysis exhibited almost no evident change compared with that before photocatalysis, indicating excellent stability of Fe@Al-ZnO photocatalyst. Due to the privileges of facile preparation, relatively low cost, powerful photocatalytic efficiency, excellent stability as well as magnetic recovery property, Fe@Al-ZnO nanocomposite was anticipated to possess remarkable potential in VLD photocatalytic inactivation of bacteria.

A novel application of In2S3 for visible-light-driven photocatalytic inactivation of bacteria: Kinetics, stability, toxicity and mechanism

Photocatalytic bacterial inactivation under visible light emerges as a new alternative to control microbial contamination by utilizing free and renewable sunlight. However, the exploration of highly effective and safe visible-light-driven (VLD) photocatalysts remains an important step toward accessing this new technology. Herein, an eco-friendly photocatalyst, namely Indium Sulfide (In2S3), was fabricated through a facile hydrothermal method for VLD photocatalytic inactivation of bacteria. The energy band gap of the as-prepared In2S3 was measured as 2.25 eV. As expected, the obtained In2S3 photocatalyst showed remarkable inactivation efficiency toward E. coli under fluorescent tubes irradiation. The photocatalytic inactivation kinetic was perfectly fitted by a mathematical model for bacteria inactivation. In addition, In2S3 exhibited high stability and could be reused. The leakage of In3+ was not significant and showed no toxic effect to the bacteria. Based on the results of scavenger study and ESR technology, the dominant reactive species causing In2S3 VLD photocatalytic bacterial inactivation were proposed as O2−, h+, H2O2 and e−, rather than OH. The SEM study suggested that the damages to the intracellular components occurred prior to the destruction of cell wall. This study provides novel application of In2S3 for VLD photocatalytic inactivation of bacteria as well as comprehensive insight into the inactivation mechanism.

Solvothermal synthesis of Ag2WO4/Sb2WO6 heterostructures for enhanced charge transfer properties and efficient visible-light-driven photocatalytic activity and stability

Visible-Light-Driven (VLD) photocatalysis for the dye waste water treatment is impeded by the immediate recombination effect and weak redox potential of the charge carriers. Here, we report the synthesis of silver and antimony tungstate-based novel hybrid composite (Ag2WO4/Sb2WO6) with significant charge carrier partition and strong redox potential for superior photocatalysis in an aqueous medium. The synthesized composite has a matching electronic band structure and synergistic effect—wherein, Ag2WO4 operates as an electron acceptor for Sb2WO6 which in return promotes photoelectron transfer; consequently, leading to charge partition and mitigation of electron-hole recombination. Relying upon the solvothermal approach, a fresh hertojunction was obtained via in-situ development of Sb2WO6 hierarchical structures on Ag2WO4 rods. Samples prepared were tested for their photocatalytic evaluation by degradation of non-azo dye rhodamine B (RhB) under visible-light subjection. The Ag2WO4/Sb2WO6 composite materials (comprising type 2 hetero-junction), displayed enhanced photocatalytic performance in comparison to the pristine Sb2WO6. In addition, the effect of the Ag2WO4 amount on photocatalytic activity was investigated. Among the four different compositions—9 wt%, 12 wt%, 15 wt%, and 18 wt% of Ag2WO4 in the composite (i.e., Ag2WO4/Sb2WO6), the composite with a 15 wt% composition of Ag2WO4 illustrated superior performance. In the case of the composite with 15-wt% of Ag2WO4, the photocatalytic degradation of RhB exhibits kapp value of 3.3 × 10−2 min-1 which is 5.4 times greater than kapp values of pristine Sb2WO6 (6.1 × 10-3 min-1). In the radical scavenger tests, ·OH and h+ were identified as the main reactive species—for which a possible photocatalytic mechanism is sketched to display the charge transfer and partition in Ag2WO4/Sb2WO6. Lastly, the composite catalyst revealed an excellent photostability with 86 % retention of photocatalytic efficiency after four catalytic cycles.

Facile construction of novel Bi2WO6/Ta3N5 Z-scheme heterojunction nanofibers for efficient degradation of harmful pharmaceutical pollutants

Pharmaceutical wastewater has become a severe, tremendous threaten to ecological environment and human health. Semiconductor photocatalysts have emerged as potential candidates for degrading pharmaceutical pollutants. Construction of highly efficient, stable and recyclable Z-scheme photocatalysts that are superior to individual constituents or widely studied heterojunction photocatalysts is very fascinating yet challenging. Herein, we report an efficient, stable and recyclable visible-light-driven (VLD) Bi2WO6/Ta3N5 Z-scheme heterojunction with compact interface contact fabricated via an electrospinning–calcination–solvothermal route, in which abundant Bi2WO6 nanosheets are in-situ, compactly and vertically grown on the surface of the Ta3N5 nanofibers. These as-fabricated Z-scheme Bi2WO6/Ta3N5 heterojunctions display dramatically enhanced VLD catalytic activity compared to pristine Bi2WO6, Ta3N5, or the mixture of Bi2WO6 and Ta3N5. Particularly, Bi2WO6/Ta3N5 (1.0Bi–Ta) presents the highest photocatalytic property for the removal of tetracycline hydrochloride (TC) and ciprofloxacin (CIP), achieving approximately 86.7% and 81.1% degradation efficiency, respectively. The extraordinary photocatalytic property is ascribed to the Z-scheme hetero-structure with unique core–shell architecture that realizes compactly interfacial contact between the components for efficient separation of photo-excited carriers, strong visible-light absorption, as well as possesses the strong oxidation ability of photo-excited hole, and the high reduction capacity of photo-excited electron. The trapping experiments combined with electron spin resonance (ESR) analyses verify the prevailing role of photo-induced holes (h+), superoxide radicals (O2−), and hydroxyl radicals (OH) in the Bi2WO6/Ta3N5 photocatalytic system. Notably, the direct contact between Bi2WO6/Ta3N5 and contaminants is experimentally demonstrated to be significant for the efficient degradation of pollutants. Moreover, Bi2WO6/Ta3N5 is endowed with easily recyclable characteristics and excellent durability. Therefore, this research illustrates that Bi2WO6/Ta3N5 may hold a great prospect for the treatment of harmful pharmaceutical pollutants.

Fabrication of hollow-catalytic microspheres (HCMs) with double-sided materials and their application on wastewater treatment

The hollow catalytic microspheres (HCMs) with double-sided structures were fabricated, in which the external and internal sides are TiO2–Ag and MgO–ZnO respectively. For a hollow catalytic microsphere (HCM), the visible-light-driven (VLD) photocatalysts (TiO2–Ag) can receive light, while the non-light-driven catalysts (MgO–ZnO) are in shadow. The characterizations demonstrated that metal oxides were loaded on the biochar microspheres and the hollow microspheres were fabricated. Moreover, the adsorption and photocatalytic behaviors of HCMs for methylene blue (MB) were explored. The results indicate that the removal rate of MB (100 mL, 25 mg/L) and chemical oxygen demand (COD) by HCMs (0.04 g) were 96.9% and 92.9% under Xe-lamp light (150 W, 8 h) irradiation, respectively. Besides, the HCMs exhibited high catalytic efficiency and stable photocatalytic capability after being utilized for five times. The possible degradation pathway of MB by HCMs was proposed.

Facile fabrication of In2O3/S-doped g-C3N4 heterojunction hybrids for enhanced visible-light photocatalytic hydrogen evolution

Graphitic carbon nitride (g-C3N4) is an attractive photocatalyst owing to its non-metallicity, suitable band gap and high physicochemical stability. Nevertheless, the photocatalytic performance of pure g-C3N4 is limited by the fast recombination of photoinduced charge carriers. In this study, we overcame this problem by constructing g-C3N4-based composites to accelerate the electron-hole separation. The photocatalytic activity of In2O3/S-doped g-C3N4 (In2O3/SCN) in visible-light-driven (VLD) hydrogen evolution was remarkably improved, which was ascribed to the inhibited charge carrier recombination.

High-efficient precious-metal-free g-C3N4-Fe3O4/β-FeOOH photocatalyst based on double-heterojunction for visible-light-driven hydrogen evolution

The two-dimensional (2D) g-C3N4 has a wide application prospect in photocatalysis field due to its larger surface reactions, wider absorption of light and faster charge separation. However, the lack of active site of reduction leads to its poor hydrogen evolution reaction (HER) activity. In this work, the intermediate β-FeOOH was synthesized as a high-efficiency precious metal free co-catalyst in hydrogen production. Then, the g-C3N4-Fe3O4/β-FeOOH (CNFF-x,y, x = 1, 2 and 3, y denotes the reaction time (h)) photocatalyst based on p-n and Z-scheme heterojunction was constructed via a subsequent solvothermal process. The chemical composition, microtopography, crystallography, photochemical and electrochemical properties of the CNFF-x,y were analyzed by XRD, FI-IR, TEM, XPS and so on. The visible-light-driven (VLD) catalytic performance of CNFF-x,y heterojunction was evaluated by the hydrogen evolution reaction (HER). Results showed that CNFF-2,10 photocatalyst based on p-n (g-C3N4-Fe3O4) and Z-scheme (Fe3O4/β-FeOOH) heterojunction presented the highest VLD catalytic HER activity (33.25 μmol g−1 h−1) at the absence of Pt co-catalyst after illumination for 6 h. It indicated that the effective introduction of Fe3O4/β-FeOOH nanoparticles (NPs) into g-C3N4 to construct double-heterojunction (g-C3N4-Fe3O4/β-FeOOH) could greatly broaden the light response property and inhibit the recombination of photo-induced carriers, exhibiting enhanced HER activity. Meanwhile, this double-heterojunction photocatalyst presented robust photostability and reproducibility even been used several times. The findings of an intermediate β-FeOOH were put forward in this study will provide some new ideas for the research of HER.

High photoresponse and fast carrier mobility: Two‐dimensional rGO‐AgBr/Ag composite based on Z‐scheme heterointerface with plasma for hydrogen evolution

With the improvement of people's living standard, energy shortage is increasingly severe. Photocatalysis technology is one of the most effective means to solve this problem. Generally, poor visible-light response and fast combination of photo-induced carriers are the main limiting factors to traditional photocatalysts. Aiming at this problem, in this paper, AgBr was used as the photosensitizer to immobilize on the surface of reduced graphene oxide (rGO) for the complexation of Ag+ ions and carboxyl groups of precursor graphene oxide (GO), then the two-dimensional rGO-AgBr/Ag composites (2D rGAA-α, α = 1, 2 and 3) were synthesized by solvothermal method. The structures, morphologies, chemical bonding states and photoelectrochemical properties of the samples were analyzed to study the samples, and the corresponding visible-light-driven (VLD) catalytic performances were studied by hydrogen evolution reaction (HER). Compared with pure rGO, the light absorption of rGAA-α was almost extended to full spectral range for the Z-scheme heterointerface (rGO-AgBr) construction, and the separation of photo-induced carriers can be promoted effectively. The HER results showed that the average hydrogen evolution rate ( ) of rGAA-α was significantly increased, and the rGAA-2 catalyst presented the highest (72.71 μmol h-1g-1). After six recycling experiments, the very faint activity decrease and unobvious structure change suggested the high photostability. Accordingly, the enhanced catalytic activity of rGAA-α catalysts was attributed to the formation of Z-scheme heterointerface and generation of Ag plasmas, so this study will provide a simple, effective and promising method for hydrogen energy development.

Fabrication of dual Z-scheme photocatalyst via coupling of BiOBr/Ag/AgCl heterojunction with P and S co-doped g-C3N4 for efficient phenol degradation

Advances in noble metal mediated Z-scheme photocatalytic system have ushered in a climax on environmental remediation. Herein, graphitic carbon nitride (GCN) and phosphorus sulphur co-doped graphitic carbon nitride (PSCN) were synthesized via calcination process. GCN, PSCN and Z-scheme visible light driven (VLD) ternary BiOBr/PSCN/Ag/AgCl nanophotocatalyst were characterized by X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–visible diffuse reflectance spectra (UV–vis DRS). BiOBr/PSCN/Ag/AgCl nanocomposite exhibited superior visible light driven photocatalytic ability as compared to pristine PSCN, AgCl and BiOBr towards degradation of phenol. The results explicated promising photocatalytic activity along with space separation of photocarriers caused via formation of BiOBr/PSCN/Ag/AgCl Z-scheme heterojunction. The visible light absorption efficacy of BiOBr/PSCN/Ag/AgCl photocatalyst was confirmed by photoluminescence (PL) spectra. Finally, recycling experiments were explored for the mechanistic detailing of phenol photodegradation employing BiOBr/PSCN/Ag/AgCl photocatalyst. After seven successive cycles photodegradation efficacy of photocatalyst was reduced to 90% from 98%. Proposed mechanism of BiOBr/PSCN/Ag/AgCl nanophotocatalyst for degradation of phenol was discussed. OH and O2− radicals were main reactive species responsible for photocatalytic phenol degradation.

In situ construction of WO3 nanoparticles decorated Bi2MoO6 microspheres for boosting photocatalytic degradation of refractory pollutants

Visible-light-driven (VLD) heterojunction photocatalysts for refractory contaminant degradation have aroused huge interest because of their outstanding photocatalytic performance. From the aspect of practical application, it is important to develop a highly efficient, durable, eco-friendly and inexpensive VLD photocatalyst. Herein, we report a novel VLD WO3/Bi2MoO6 heterojunction photocatalyst with remarkable photocatalytic activity, which was fabricated via an electrospinning–calcination–solvothermal route. The phase, composition, morphologies, and optical properties of WO3/Bi2MoO6 heterojunctions were comprehensively characterized. The photocatalytic performance of WO3/Bi2MoO6 heterojunctions was assessed by the removal of rhodamine (RhB) and tetracycline hydrochloride (TC) under visible light (VL). WO3/Bi2MoO6 heterojunctions displayed superior photocatalytic activities compared to Bi2MoO6, WO3, or the mechanical mixture of WO3 and Bi2MoO6. In particular, the heterojunction material (0.4WB, theoretical molar ratio of WO3/Bi2MoO6 is 0.4/1.0) exhibited the best degradation efficiency (100%) and mineralization rate (52.3%) in 90 min, both of which exceeded the observed rates for Bi2MoO6 by 5.3 and 6.4 times, respectively. Moreover, 0.4WB showed a good durability in eight runs. The optimized photocatalytic property of WO3/Bi2MoO6 can be attributed to enhanced VL absorption and reduced recombination efficiency of carriers owing to the synergistic effects between Bi2MoO6 and WO3. The necessity of direct contact between WO3/Bi2MoO6 and contaminants was experimentally verified. The study on photocatalytic mechanism demonstrates that superoxide free radicals (O2−) and photo-generated hole (h+) are dominantly responsible for the pollutant degradation, as demonstrated by the trapping experiments and electron spin resonance (ESR) analysis. Therefore, the WO3/Bi2MoO6 heterojunction holds huge potential to be utilized as a durable and highly active photocatalyst for wastewater treatment.

Facile construction of flower-like bismuth oxybromide/bismuth oxide formate p-n heterojunctions with significantly enhanced photocatalytic performance under visible light

Visible-light harvesting ability and charge separation efficiency are two pivotal factors for the design and construction of photocatalysts with an efficient ability for degrading toxic pollutants. Herein, visible-light-driven (VLD) BiOBr/BiOCOOH p-n heterojunction photocatalysts were prepared via an in-situ anion-exchange route. Through controlling the addition of KBr, we synthesized a series of BiOBr/BiOCOOH p-n heterojunctions with a different BiOBr loading. During the process, BiOBr production and homogeneous deposition on BiOCOOH with close interfacial interactions were realized by employing BiOCOOH microspheres as the self-sacrificing template. Compared to bare BiOBr and BiOCOOH, such p-n heterojunctions displayed dramatically strengthened performance in decomposing the industrial dye (rhodamine B, RhB) and antibiotic (tetracycline chloride, TC) under the irradiation of visible light. Among them, BiOBr/BiOCOOH p-n heterojunction with a BiOBr/BiOCOOH theoretical molar ratio of 0.6/0.4 (0.6Br-Bi) achieved the highest performance. Moreover, 0.6Br-Bi showed a good durability, indicating BiOBr/BiOCOOH p-n heterojunction possessed an excellently stable photocatalytic activity. Such an efficient and stable photocatalytic performance was mainly due to the formation of p-n heterojunctions which can profoundly improve the visible-light absorption and significantly depress the recombination of charge carriers. Trapping experiments and ESR tests verified that superoxide free radicals (O2−) and photogenerated hole (h+) played a significant role in RhB degradation. This research affords a promising p-n heterojunction catalyst for wastewater treatment.

Photo-removal of 2,2′4,4′-tetrabromodiphenyl ether in liquid medium by reduced graphene oxide bridged artificial Z-scheme system of Ag@Ag3PO4/g-C3N4

2,2′,4,4′-Tetrabrominateddiphenyl ether (BDE-47), as one of polybrominated diphenyl ethers (PBDEs), has been proven to be global contaminant owing to widespread utilization as flame retardant. Herein, a novel visible-light-driven (VLD) artificial indirect Z-scheme system of Ag@Ag3PO4/g-C3N4/rGO is finely designed for BDE-47 removal assisted with abundant solar energy. The novel hybrid composite exhibits an enhanced reductive debromination activity with removal efficiency of 93.4% under visible light irradiation (λ > 420 nm) for 120 min, which is 173.65 times higher than pristine g-C3N4 catalyst. A series of experiments in terms of the environmental effects of initial concentration, pH, solvent and light source are performed to optimize the photocatalytic performance. The presence of rGO as an excellent storing and shuttling medium, can further facilitate the charge carrier separation in the indirect Z-scheme system for the enhanced photo-reduction debromination performance. The accumulated electrons on the solid catalyst can attack the ortho-Br of BDE-47 to formation of BDE-28, and then so on. The protons (H+) can be reduced to atomic hydrogen (H°), which can greatly weaken para-Br of BDE-47 to generation of BDE-17. Furthermore, the remaining holes can react with CH3OH to generate CH2OH radical, and then further directly produce electron for debromination process. A possible debromination pathway for BDE-47 was proposed. This work provides a green and promising strategy utilizing solar energy to remove BDE-47 in the liquid medium by virtue of VLD composite.

Photocatalytic removal of diclofenac by Ti doped BiOI microspheres under visible light irradiation: Kinetics, mechanism, and pathways

BiOI microspheres doped with different amounts of Ti were fabricated and used to remove diclofenac (DCF) from water under visible light irradiation. The fabricated photocatalysts were well characterized. Ti doped BiOI microspheres were found to exhibit higher photocatalytic activity towards DCF under visible light compared with BiOI. Ti doping broadened the band gap of BiOI, which leads to a more negative conduction band edge and a higher reducing activity of photo-generated electrons, thus facilitates ·O2− production during photocatalysis. Among all the fabricated Ti doped BiOI microspheres, TB450 exhibited the highest DCF photocatalytic removal efficiency. Specifically, 99.2% of DCF (C0 = 10 mg L−1) was removed by TB450 (250 mg L−1) at pH 5 within 90 min under visible light irradiation. Scavenger experiments indicated that active species including h+, ·O2− and H2O2 played important roles in the photocatalytic process. The degradation pathway of DCF was elucidated by theoretical density functional theory (DFT) and by-products identification through liquid chromatograph mass spectrometer (LC-MS) analysis. DCF degradation pathway mainly included hydroxylation and the cleavage of CN bond. DFT calculation can well interpret the degradation mechanism and the sites of DCF molecule with high radical-attack Fukui index (f0) exhibit high reactivity. Acidic condition was found to facilitate the DCF photocatalytic removal. Due to strong photo-stability, Ti doped BiOI microspheres contained good visible-light-driven (VLD) photocatalytic removal efficiency for DCF in the fourth consecutive reused cycle. Ti doped BiOI microspheres can be employed as a cost-effective and high-efficient material to efficiently degrade emerging contaminants (e.g., pharmaceutical) from wastewaters under visible light conditions.

Heterojunctions of β-AgVO3/BiVO4 composites for enhanced visible-light-driven photocatalytic antibacterial activity

β-AgVO3/BiVO4 composite visible light driven (VLD) photocatalytic antibacterial materials with a heterojunction structure were synthesized through a simple one-pot hydrothermal approach. The synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectra, and UV–visible diffuse reflectance spectra techniques, respectively. β-AgVO3/BiVO4 composite materials exhibit enhanced photocatalytic antibacterial activities against typical marine fouling bacteria (Pseudomonas aeruginosa) under visible light irradiation, which can be attributed to the involving of β-AgVO3 to form a heterojunction structure. The heterojunction greatly increases the separation extent and the lifetime of the photogenerated charges in the composite material. The 20% β-AgVO3/BiVO4 sample has the best VLD photocatalytic antibacterial performance. Under 30 min visible light irradiation, its antibacterial rate can reach 99.99%. The superoxide radical (⋅O2−) and holes (h+) are main active species in the VLD photocatalytic antibacterial process on the basis of the radical trapping experiment results. Furthermore, a high photocatalytic antibacterial activity can be kept after 5 cycles, suggesting high stability of β-AgVO3/BiVO4. Materials obtained in the present work can be potentially applied in practical antibacterial fields.

Facile Synthesis of Bi2MoO6 Microspheres Decorated by CdS Nanoparticles with Efficient Photocatalytic Removal of Levfloxacin Antibiotic

Developing high-efficiency and stable visible-light-driven (VLD) photocatalysts for removal of toxic antibiotics is still a huge challenge at present. Herein, a novel CdS/Bi2MoO6 heterojunction with CdS nanoparticles decorated Bi2MoO6 microspheres has been obtained by a simple solvothermal-precipitation-calcination method. 1.0CdS/Bi2MoO6 has stronger light absorption ability and highest photocatalytic activity with levofloxacin (LEV) degradation efficiency improving 6.2 or 12.6 times compared to pristine CdS or Bi2MoO6. CdS/Bi2MoO6 is very stable during cycling tests, and no appreciable activity decline and microstructural changes are observed. Results signify that the introduction of CdS could enhance the light absorption ability and dramatically boost the separation of charge carriers, leading to the excellent photocatalytic performance of the heterojunction. This work demonstrates that flower-like CdS/ Bi2MoO6 is an excellent photocatalyst for the efficient removal of the LEV antibiotic.

Fabrication of visible-light-driven silver iodide modified iodine-deficient bismuth oxyiodides Z-scheme heterojunctions with enhanced photocatalytic activity for Escherichia coli inactivation and tetracycline degradation

At present, various organic pollutants and pathogenic microorganisms presented in wastewater have severely threatened aquatic ecosystem and human health. Meanwhile, semiconductor photocatalysis technology for water purification has attracted increasingly significant attention. Herein, we successfully constructed a series of novel visible-light-driven (VLD) Bi4O5I2/AgI hybrid photocatalysts with different AgI amounts. Compared with pristine AgI and Bi4O5I2, Bi4O5I2/AgI with the optimal AgI contents exhibited remarkably enhanced photocatalytic performance in probe experiment for Escherichia coli (E. coli) disinfection and tetracycline (TC) degradation. The efficiency for TC degradation and E. coli inactivation reached 82% and 100% in 30 min, respectively. The enhanced electron-hole separation efficiency was responsible for improved photocatalytic activity. In addition, the destruction process of the chemical structure of TC molecules was further investigated by three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs). The activity and crystal phase of the catalysts did not change significantly after four cycles, demonstrating their excellent recyclability and stability of catalysts. The Ag+ ion leaking experiments, radical trapping experiments and ESR tests demonstrated that OH, O2− and h+ were the main active species in photocatalytic disinfection processes. Furthermore, the photocatalytic mechanism of Bi4O5I2/AgI nanomaterials was discussed in detail in conjunction with the energy band structure, and a reasonable Z-scheme interfacial charge transfer mechanism was proposed. This work is expected to provide an efficient water disinfection method.