RGO-Promoted All-Solid-State g-C3N4/BiVO4 Z-Scheme Heterostructure with Enhanced Photocatalytic Activity toward the Degradation of Antibiotics

Z-Scheme BiVO4/g-C3N4 Photocatalyst-With or Without an Electron Mediator?

The hybrid system BiVO4/g-C3N4 is a prospective photocatalyst because of the favorable mutual alignment of the energy bands of both semiconductors. However, the path of the photocatalytic process is still unclear because of contradictory information in the literature on whether the mechanism of charge carrier separation at the BiVO4/g-C3N4 interface is band-to-band or Z-scheme. In this work, we clarified this issue by comparative photocatalytic studies with the use of systems without a mediator and with different kinds of mediators including Au nanoparticles, fullerene derivatives, and the Fe3+/Fe2+ redox couple. Additionally, the charge transfer dynamics at the BiVO4/g-C3N4 and BiVO4/mediator/g-C3N4 interfaces were investigated by time-resolved photoluminescence (TRPL) measurements, while the influence of the mediator on the surface recombination of the charge carriers was verified by intensity-modulated photocurrent spectroscopy (IMPS). We proved that the charge carrier separation at the BiVO4/g-C3N4 interface occurs according to the mechanism typical for a heterojunction of type II, while the incorporation of the mediator between BiVO4 and g-C3N4 leads to the Z-scheme mechanism. Moreover, a very strong synergetic effect on caffeine (CAF) degradation rate was found for the system BiVO4/Au/g-C3N4 in the presence of Fe3+ ions in the CAF solution.

Light-driven photocatalysis as an effective tool for degradation of antibiotics

Antibiotic contamination has become a severe issue and a dangerous concern to the environment because of large release of antibiotic effluent into terrestrial and aquatic ecosystems. To try and solve these issues, a plethora of research on antibiotic withdrawal has been carried out. Recently photocatalysis has received tremendous attention due to its ability to remove antibiotics from aqueous solutions in a cost-effective and environmentally friendly manner with few drawbacks compared to traditional photocatalysts. Considerable attention has been focused on developing advanced visible light-driven photocatalysts in order to address these problems. This review provides an overview of recent developments in the field of photocatalytic degradation of antibiotics, including the doping of metals and non-metals into ultraviolet light-driven photocatalysts, the formation of new semiconductor photocatalysts, the advancement of heterojunction photocatalysts, and the building of surface plasmon resonance-enhanced photocatalytic systems.

Selective efficient photocatalytic degradation of antibiotics and direct Z-type migration pathway for hierarchical core-shell TiO2/g-C3N4 composites

Constructing superior Z-type photocatalytic heterojunction is beneficial to effectively enlarge interface contact, improve the photo-generated carrier separation rate, and retain the high redox ability. In this work, we designed a hierarchical core-shell g-C3N4/TiO2 structure to build Z-type heterojunction via combining simple template method and pyrolysis process. A close-knit Z-type heterojunction was constructed using TiO2 as a thick core and g-C3N4 as an ultra-thin shell. The effects of lamp source, wavelength, tetracycline (TC) concentration, and photocatalyst dose on the degradation performance on TC of g-C3N4/TiO2 were inspected. 0.1TiO2/g-C3N4 photocatalyst had the best degradation rate and highest removal rate within 30 min, and its degradation rate was about 49, 23, and 5 times than pure g-C3N4, TiO2, and commercial TiO2/g-C3N4 in respect. Moreover, compared with degradation ability under Xenon lamp, LED irradiation for g-C3N4/TiO2 composites showed a remarkable selective degradation. The fast and efficient Z-type transfer pathway of 0.1 g-C3N4/TiO2 was realized by forming an optimized interface and abundant surface active sites ascribed to the combined action of thick TiO2 core and ultra-thin g-C3N4 shell. In addition, the degradation intermediates were analyzed by LC-MS and suggested pathways of degradation. The work could provide novel design concept to obtain reliable Z-type photocatalysts with hierarchical core-shell structure applied in degradation of antibiotic wastewater.

Carbon quantum dots (CQDs) mediated Z-scheme g-C3N4-CQDs/BiVO4 heterojunction with enhanced visible light photocatalytic degradation of Paraben

The construction of a novel Z-scheme system which possesses superior charge separation and high redox ability is highly desirable for efficient photocatalytic degradation of organic pollutants. Herein, a carbon quantum dots (CQDs) modified g-C₃N₄ (GCN) and BiVO₄ (BVO) composite (GCN-CQDs/BVO) was fabricated via an initial loading of CQDs on GCN, and a subsequent combination with BVO during its hydrothermal synthesis. Physical characterization (e.g. TEM, XRD, XPS) verified the intimate heterojunction structure of the composite, while CQDs improved its light absorption. The band structures of GCN and BVO were evaluated, displaying the feasibility for Z-scheme formation. In comparison with GCN, BVO, and GCN/BVO, GCN-CQDs/BVO generated the highest photocurrent and lowest charge transfer resistance, inferring the prominently improved charge separation. Under visible light irradiation, GCN-CQDs/BVO exhibited the significantly enhanced activity in degrading the typical Paraben pollutant--benzyl paraben (BzP), achieving the removal of 85.7% in 150 min. The effects of various parameters were explored, demonstrating that neutral pH was optimal, while coexisting ions (CO₃^2-, SO₄^2-, NO₃^-, K⁺, Ca²⁺, Mg²⁺) and humic acid impacted the degradation negatively. Meanwhile, trapping experiments and electron paramagnetic resonance (EPR) technique revealed that superoxide radicals (•O₂^-) and hydroxyl radical (•OH) were primarily responsible for BzP degradation by GCN-CQDs/BVO. In particular, with the assistance of CQDs, the generation of •O₂^- and •OH was notably augmented. Based on these results, a Z-scheme photocatalytic mechanism was proposed for GCN-CQDs/BVO, where CQDs acted as electron mediators to combine the holes from GCN and electrons from BVO, resulting in significantly improved charge separation and maximized redox ability. Moreover, the toxicity of BzP was remarkably reduced during the photocatalytic process, emphasizing its great potential in abating the risk of Paraben pollutants.

Boosting photocatalytic performances of lamellar BiVO4by constructing S-scheme heterojunctions with AgBr for efficient charge transfer

Successful construction of heterojunction can improve the utilization efficiency of solar light by broadening the absorption range, facilitating charge-carrier separation, promoting carrier transportation and influencing surface-interface reaction. Herein, visible-light-driven AgBr was deposited on the surface of lamellar BiVO₄which was prepared by a facile hydrothermal process to improve charge carrier separation, and subsequent photocatalytic effectiveness. The catalyst with an optimal AgBr/BiVO₄ratio exhibited a superbly enhanced photocatalytic decolorization ability (about 6.85 times higher than that of pure BiVO₄) and high stability after four cycles. The unique photocatalytic mechanism of S-scheme carrier migration was investigated on the bases of radical trapping tests and photo/electrochemical characterizations. Results showed that the enhanced migration strategy and intimately interfacial collaboration guaranteed the effective charge carriers separation/transfer, leading to magnificent photocatalytic performance as well as excellent stability.

Fabrication of novel BiVO4/Bi2O3heterostructure with superior visible light induced photocatalytic properties

Heterostructure BiVO₄/Bi₂O₃nanocomposites with enhanced visible light activity are effectively synthesized through an easiest and single step hydrothermal route, using bismuth subnitrate and ammonium meta-vanadate as main raw materials in existence of citric acid. The phase and surface structure, topography and optical properties of synthesized composites are characterized by XRD, SEM, EDX, FTIR, UV-Visible and PL spectroscopy. It was found that 5%BiVO₄/Bi₂O₃(BOBV-5) nanocomposite exhibit excellent photocatalytic performance for rhodamine B dye degradation and tetracyclic under irradiation of visible light as compared to single component i.e. BiVO₄. The increased photocatalytic activity should be ascribed for making p-n heterojunction among p-type Bi₂O₃and n-type BiVO₄. This p-n heterojunction successfully reduce the recombination of photogenerated charge carriers. Furthermore, the BOBV-5 novel photocatalyst shows good stability in constructive five cycles and photocatalytic activity is best for conquering photo corrosion of a photocatalysts. To explain charge migration route, whole photocatalytic mechanism was described in terms of energy band structures. Furthermore, the present work is helpful effort for design of new visible light photocatalytic materials with heterojunction structures.

Direct Z-scheme mediated SmVO4/UiO-66-NH2 heterojunction nanocomposite for the degradation of antibiotic tetracycline hydrochloride molecules under sunlight

The use of tetracycline hydrochloride (TCH) for veterinary, human therapy, and agriculture has risen in the past few decades, making it to become one of the most exploited antibiotics. However, TCH residue in the environment is causing issues related to the evolution of antibiotic-resistant bacteria. To address such a problem, photodegradation offers a potential solution to decompose these pollutants in wastewater and thereby mitigates negative environmental impacts. In this context, the research focuses on the use of the rare-earth metal oxide samarium orthovanadate (SmVO₄) with nanorod structure, coupled with UiO-66-NH₂ for the photocatalytic degradation. Their photocatalytic activity to degrade antibiotic TCH molecules is explored under simulated solar light irradiation. The integration of UiO-66-NH₂ with SmVO₄ enhanced the light absorption, recombination resistance, carrier lifetime (from 0.382 to 0.411 ns) and specific surface area (from 67.17 to 246 m²/g) of the composite system as confirmed from multiple analyses. The obtained results further indicated that SmVO₄/UiO-66-NH₂ nanocomposites could form a direct Z-scheme based heterojunction. Such mechanism of charge transfer leads to the effective degradation of TCH molecules up to 50% in 90 min under solar light, while it is degraded only 30% in the case of bare-SmVO₄ nanorods. In this work, the incorporation of UiO-66-NH₂ positively influences photoelectrochemical properties and improves the overall photoredox properties of SmVO₄ for the degradation of complex compounds like antibiotic TCH molecules. Therefore, UiO-66-NH₂ can be proposed as an effective material to sensitize the rare-earth based photocatalytic material.

Synchronous removal of tetracycline and copper (II) over Z‑scheme BiVO4/rGO/g-C3N4 photocatalyst under visible-light irradiation

The combined pollution of heavy metals and organic pollutants in water body has become one of vital environmental issues. Herein, a series of BiVO₄/rGO/g-C₃N₄ nanocomposites were synthesized for concurrent removals of organic pollutant and heavy metal. Results showed that using the optimized photocatalyst BiVO₄/rGO/g-C₃N₄-28, tetracycline (TC) removal of 87.3% and copper (Cu (II)) removal of 90.6% were achieved under visible-light irradiation within 3 h, respectively; much higher than those using BiVO₄ and g-C₃N₄. More importantly, synergistic effect of TC and Cu (II) removals occurred on the surface of BiVO₄/rGO/g-C₃N₄ in the TC-Cu (II) coexistence condition. Additionally, the ·OH and ·O₂- were the most important active species for TC oxidation, while photogenerated electrons were the most responsible for Cu (II) reduction. Results of various characterizations and electron spin resonance test demonstrated that BiVO₄/rGO/g-C₃N₄ was a Z-scheme photocatalyst. Based on the identified intermediates, possible degradation pathways and mechanisms for photocatalytic degradation of TC were proposed. This study advances the development and mechanism of photocatalysts for collaborative removal of pollutants.

Enhanced photocatalytic degradation of paraben preservative over designed g-C3N4/BiVO4 S-scheme system and toxicity assessment

Paraben preservatives have been listed as emerging pollutants due to their ubiquity in various environmental matrices, especially the water bodies. How to efficiently and practically eliminate these paraben pollutants is therefore of great importance. Herein, a designed S-scheme heterojunction photocatalyst, consisting of graphitic carbon nitride (g-C₃N₄) and monoclinic bismuth vanadate (BiVO₄), was fabricated by a facile hydrothermal synthesis and employed to treat benzyl-paraben (BzP). TEM and XPS analysis testified the intimate interaction between g-C₃N₄ and BiVO₄, and the consequently smoothed interfacial charge transfer rendered the feasible recombination of the photoexcited electrons (from BiVO₄) and holes (from g-C₃N₄). The as-established S-scheme system enabled the left g-C₃N₄ electrons and BiVO₄ holes to maintain the high redox abilities and accelerated the charge separation concurrently. In particular, the g-C₃N₄/BiVO₄ composite generated much higher photocurrent response as compared with pure g-C₃N₄ and BiVO₄, highlighting the improved separation of photoinduced charges. Therefore, under visible light and natural solar light irradiation, the g-C₃N₄/BiVO₄ composite showed the significantly enhanced photocatalytic degradation of BzP, which was further optimized with 5 wt% g-C₃N₄ in the composite. According to the Mott-Schottky plots and identified active species, the mechanism of the g-C₃N₄/BiVO₄ S-scheme heterojunction system was illustrated. In addition, during the photocatalytic degradation process, the acute toxicity of the reaction solutions on zebrafish embryos was notably reduced. In conclusion, the demonstrated strategy to enhance the photocatalytic performance by designing S-scheme heterostructure may provide more insights into the development of high-efficiency photocatalyst towards the solar energy utilization and environmental treatment. Furthermore, photocatalytic degradation had been proved to be an efficient method for eliminating the ecological risk of paraben pollutants, warranting more attention in future work.

Theoretical and experimental studies of high efficient all-solid Z-scheme TiO2-TiC/g-C3N4 for photocatalytic CO2 reduction via dry reforming of methane

All-solid Z-scheme heterojunction TiO2-TiC/g-C3N4 was proposed and synthesized successfully by a facile calcination method and used for photocatalytic CO2 reduction in the presence of CH4. Under sub-atmospheric pressure and room...

Construction of a Z-scheme g-C3N4/NBGO/BiVO4 heterostructure with visible-light driven photocatalytic degradation of tetracycline: efficiency, reaction pathway and mechanism

In this study, an aminated graphene-like biochar (NGBO) was used as a solid-state electron mediator at a g-C3N4/BiVO4 interface to construct a hybrid Z-scheme system (g-C3N4/NBGO/BiVO4) for the photocatalytic degradation of tetracycline (TC) from aqueous solutions.

Facile preparation of bismuth vanadate-sheet/carbon nitride rod-like interface photocatalyst for efficient degradation of model organic pollutant under direct sunlight irradiation

The photocatalytic performance of a semiconducting catalytic system is strongly influenced by charge-carrier separation rate, charge transport properties, surface area, utilization of light energy, and interface bonding. Herein, a series of bismuth vanadate (BiVO₄) samples were prepared via hydrothermal method by changing the volume ratios of ethelene glycol and ethanol as a solvent mixture for bismuth precursors. Further, the optimized BiVO₄ sheets with hierarchical morphology were used to construct an interface with rod-like g-C₃N₄ materials, which was confirmed by HRSEM and HRTEM. Due to the formation of an effective interface bonding between BiVO₄/g-C₃N₄, the photoinduced charge carrier's recombination rate was suppressed as confirmed by the PL analysis. The prepared BiVO₄/g-C₃N₄ sample were used to assess the photodegradation efficiency of Rhodamine B (RhB) under direct sunlight irradiation and the photocatalysts degraded ~92.8% of RhB within 2 h. The TOC measurements revealed a 66.4% mineralization efficiency for RhB. In addition, the radical trapping experiments demonstrated that superoxide and hydroxyl radicals are the main reactive species for the degradation. Based on the experimental evidences, a plausible charge transfer mechanism has been proposed. The enhanced photocatalytic activity has been mainly attributed to the inhibition of the recombination rate, enhanced charge carrier transfer efficiency, and high rate of production of reactive species.

Carbon nanotubes as electronic mediators combined with Bi2MoO6and g-C3N4to form Z-scheme heterojunctions to enhance visible light photocatalysis

In this paper, Z-scheme Bi₂MoO₆/CNTs/g-C₃N₄composite photocatalysts were prepared through a simple hydrothermal method. The analysis was performed by XRD, FT-IR, SEM, EDS, TEM, HRTEM, XPS, BET, UV-Vis diffuse reflectance and PL spectrums. Various analyses show that CNTs not only act as excellent charge transfer bridges, but also enable a formation of the Z-scheme of charge transfer mechanism between Bi₂MoO₆and g-C₃N₄. This process not only effectively isolates electrons and holes, but also prolongs electron-hole pair lifetimes, resulting in a substantial improvement in the photocatalytic performance of the composite photocatalyst. Best photocatalytic degradation performance was shown by Bi₂MoO₆/CNTs/g-C₃N₄composite photocatalyst under simulated sunlight, while the composite photocatalyst still maintained extremely high degradation performance in cycling tests.

A review of bismuth-based photocatalysts for antibiotic degradation: Insight into the photocatalytic degradation performance, pathways and relevant mechanisms

The intensive production and utilization of antibiotics worldwide has inevitably led to releases of very large amounts of these medicines into the environment, and numerous strategies have recently been developed to eliminate antibiotic pollution. Therefore, bismuth-based photocatalysts have attracted much attention due to their high adsorption of visible light and low production cost. This review summarizes the performance, degradation pathways and relevant mechanisms of typical antibiotics during bismuth-based photocatalytic degradation. First, the band gap and redox ability of the bismuth-based catalysts and modified materials (such as morphology, structure mediation, heterojunction construction and element doping) were compared and evaluated. Second, the performance and potential mechanisms of bismuth oxides, bismuth sulfides, bismuth oxyhalides and bismuth-based metal oxides for antibiotic removal were investigated. Third, we analysed the effect of co-existing interfering substances in a real water matrix on the photocatalytic ability, as well as the coupling processes for degradation enhancement. In the last section, current difficulties and future perspectives on photocatalytic degradation for antibiotic elimination by bismuth-based catalysts are summarized. Generally, modified bismuth-based compounds showed better performance than single-component photocatalysts during photocatalytic degradation for most antibiotics, in which h⁺ played a predominant role among all the related reactive oxygen species. Moreover, the crystal structures and morphologies of bismuth-based catalysts seriously affected their practical efficiencies.

Visible light driven reduced graphene oxide supported ZnMgAl LTH/ZnO/g-C3N4 nanohybrid photocatalyst with notable two-dimension formation for enhanced photocatalytic activity towards organic dye degradation

In this study, 2D/2D/2D heterostructured r-GO/LTH/ZnO/g-C₃N₄ nanohybrid were synthesized through hydrothermal method. The strong electrostatic interaction between the negatively charged g-C₃N₄ and r-GO nanosheets with positively charged layered triple hydroxide (LTH) nanosheets are effectively influences the successful formation of heterojunction. The LTH nanosheets are well spread on the g-C₃N₄ nanosheets combined with r-GO. In particular, the as prepared heterojunction shows a better photocatalytic degradation activity compared to pristine samples and the significant enhancement in the photocatalytic performance is mainly accredited to the large interfacial charge transition of photogenerated charge carriers under the visible light irradiation. Although the 2D/2D/2D heterojunction effectively hinders the charge carrier recombination resulting high photocatalytic activity with good stability. In addition, the r-GO supported LTH/ZnO/g-C₃N₄ heterojunction shows high photo-stability after sequential experimental runs with no obvious change in the dye degradation process. Consequently, the role of active species was investigated over the r-GO/LTH/ZnO/g-C₃N₄ heterojunction with the help of different scavengers.

Insights into the Mechanism of the Bi/BiVO4 Composites for Improved Photocatalytic Activity

The increasing concentration of residual ciprofloxacin (CIP) can cause potential harm to the environment. Photocatalysis has been regarded as an effective method for the degradation of CIP. Bi/BiVO4 with excellent photocatalytic performance was synthesized partial reduction with NaBH4. The structure, morphology, composition, and optical performance of BiVO4 and Bi/BiVO4 were characterized by a variety of techniques. The results showed that the Bi/BiVO4 exhibits high photocatalytic activity in the degradation of CIP. Comparison of BiVO4 and Bi/BiVO4 has lower photoluminescence intensity and higher photocurrent responses intensity. The introduction of Bi made Bi/BiVO4 have a higher charge separation efficiency and generate more active free radicals. In addition, the radical trapping experiments revealed that superoxide free radicals and holes were the main active free radicals during the degradation of CIP. The pathway of CIP degradation was investigated through high performance liquid chromatography-mass spectrometry, and a possible degradation mechanism was proposed.

A biochar-promoted V2O5/g-C3N4 Z-Scheme heterostructure for enhanced simulated solar light-driven photocatalytic activity

A ternary biochar/vanadium pentoxide/graphite like carbon nitride (BC/V₂O₅/g-C₃N₄ denoted BC/VO/CN) composite was prepared by a simple hydrothermal method and its photocatalytic performance was investigated under simulated solar irradiation. The BC/VO/CN was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and photoluminescence spectroscopy. Within the BC/VO/CN composites VO nanoparticles were highly crystalline and intertwined with the lamellas of CN, resulting in the formation of well-defined Z-type heterostructures. The photocatalytic activity was evaluated using Rhodamine B as a model pollutant. Under simulated solar (230–780 nm) irradiation the as-prepared BC/VO/CN hybrid materials demonstrated highly improved photocatalytic activity compared to CN, VO and VO/CN. The cause of the solar enhancement could be ascribed to the formation of Z-type heterojunctions between VO and CN, which promoted faster electron–hole separation and more efficient charge transfer. BC, as an electron transfer medium, accelerated the transfer of photogenerated charge carriers and inhibited their recombination.

A Z-scheme heterojunction is formed between g-C₃N₄ and V₂O₅. As electron transfer, BC makes the photogenerated carriers separate quickly and effectively.

Azobenzene-modified Ag/Ag2O/CN photocatalysts with photoresponsive performance for controllable photodegradation of tetracyclines

In this work, an Azo@Ag/Ag₂O/CN composite photocatalyst with light-responsive performance was successfully prepared by precipitation and emulsion polymerization. Azo@Ag/Ag₂O/CN exhibits cis-trans isomerism under different light exposures.

Fe3O4-Loaded g-C3N4/C-Layered Composite as a Ternary Photocatalyst for Tetracycline Degradation

A ternary photocatalyst, Fe₃O₄-loaded g-C₃N₄/C-layered composite (g-C₃N₄/C/Fe₃O₄) was fabricated by a facile sonication and in situ precipitation technique. Carbon nanosheets were prepared using the remaining non-metallic components of waste printed circuit boards as carbon sources. In this hybrid structure, g-C₃N₄ was immobilized on the surfaces of carbon nanosheets to form a layered composite, and 10-15 nm Fe₃O₄ nanoparticles are uniformly deposited on the surface of the composite material. The photocatalytic performance of the catalyst was studied by degrading tetracycline (TC) under simulated sunlight. The results showed that the photoactivity of the g-C₃N₄/C/Fe₃O₄ composite to TC was significantly enhanced, and the degradation rate was 10.07 times higher than that of pure g-C₃N₄, which was attributed to Fe₃O₄ nanoparticles and carbon nanosheets. Carbon sheets with good conductivity are an excellent electron transporter, which promotes the separation of photogenerated carriers and the Fe₃O₄ nanoparticles can utilize electrons effectively as a center of oxidation-reduction. Moreover, a possible photocatalytic mechanism for the excellent photocatalytic performance was proposed.

Microwave-assisted synthesis of 3D Bi2MoO6 microspheres with oxygen vacancies for enhanced visible-light photocatalytic activity

Oxygen vacancies (OVs) defects in metal oxide-based photocatalysts play a crucial role in improving the charge carrier separation efficiencies to enhance the photocatalytic performances. In this work, OVs were introduced in 3D Bi₂MoO₆ microspheres through a facile and fast microwave-assisted method via the modulation of tetramethylethylenediamine (TMEDA). EPR, Raman and XPS results demonstrated that large amounts of oxygen vacancies were formed on the surface of BMO microspheres. The photocatalytic properties of the samples were studied by degradation of tetracycline (TC) under visible light. The optimal Bi₂MoO₆ with OVs exhibited optimum photocatalytic activity, and the degradation rate was 7.0 times higher than that of pristine Bi₂MoO₆. This enhancement can be attributed to the 3D structure furnishing more surface active sites and suitable OVs defects favoring the electron-hole separation. Moreover, the defective Bi₂MoO₆ microspheres exhibit high stability because the photocatalytic activity remains almost unchanged after 5 cycles, making them favorable for practical applications. Finally, a possible visible light photocatalysis mechanism for the degradation of TC was tentatively proposed.

Novel g-C3N4/Fe-ZnO/RGO nanocomposites with boosting visible light photocatalytic activity for MB, Cr (VI), and outstanding catalytic activity toward para-nitrophenol reduction

A novel g-C₃N₄/Fe-ZnO/RGO nanocomposite has been synthesized using the facile solvothermal method to boost the catalytic efficiency of ZnO. The structure and morphology of nanocomposites were examined by a wide range of characterization methods. The obtained g-C₃N₄/Fe-ZnO/RGO nanocomposite (Z-scheme heterostructure) exhibits improved photocatalytic activity toward the photodegradation of MB, Cr (VI) under visible-light irradiation and 4-nitrophenol reduction. The enhancement in activity of nanocomposite is ascribed to a unique heterostructure system, which facilitates excellent transport and separation of the photogenerated charge carrier, resulting in prolonged lifetime leading to continuous generation of reactive species. Moreover, the synergistic effect on the interface of ZnO and g-C₃N₄ and the introduction of reduced graphene oxide (RGO) serve as a booster for charge separation at the Z-scheme, which ultimately speeds up the degradation of pollutants. The present study provides a novel and facile approach for establishing an efficient nanocomposite for environmental remediation.

Facile Fabrication of C-TiO2 Nanocomposites with Enhanced Photocatalytic Activity for Degradation of Tetracycline

Visible-lightdriven C-TiO₂ nanocomposites were prepared via a simple calcination and acid etching process. The C-TiO₂ nanocomposites were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and high-resolution TEM. The results showed that TiO₂ nanoparticles were combined with a porous carbon layer through surface C-O groups, which facilitates the strong interface interaction. The interface combination of nano-TiO₂ and carbon material increases the specific surface area of nano-TiO₂, widens the range of light response, and improves the efficiency of light-induced electron migration. The visible-light photocatalytic activity of the prepared photocatalyst was evaluated by the decomposition of tetracycline aqueous solution. Compared with that of pure TiO₂, the photocatalytic activity of C-TiO₂ nanocomposites was significantly improved. Furthermore, a possible photocatalytic mechanism was also tentatively proposed. This work can promote the development of active photocatalysts under solar light for the photodegradation of environmental pollutants.

A review of graphene-based nanomaterials for removal of antibiotics from aqueous environments

Antibiotics as emerging pharmaceutical pollutants have seriously not only threatened human life and animal health security, but also caused environmental pollution. It has drawn enormous attention and research interests in the study of antibiotics removal from aqueous environments. Graphene, an interesting one-atom-thick, 2D single-layer carbon sheet with sp² hybridized carbon atoms, has become an important agent for removal of antibiotic, owing to its unique physiochemical properties. Recently, a variety of graphene-based nanomaterials (GNMs) are reported to efficiently remove antibiotics from aqueous solutions by different technologies. In this review, we summarize different structure and properties of GNMs for the removal of antibiotics by adsorption. Meanwhile, advanced oxidation processes (AOPs), such as photocatalysis, Fenton process, ozonation, sulfate radical and combined AOPs by the aid of GNMs are summarized. Finally, the opportunities and challenges on the future scope of GNMs for removal of antibiotics from aqueous environments are proposed.

Facile photo-ultrasonic assisted reduction for preparation of rGO/Ag2CO3 nanocomposites with enhanced photocatalytic oxidation activity for tetracycline

Various antibiotics in the aquatic systems have threat the aquatic ecosystem balance and the human health. In this study, a degradation treatment method for tetracycline (TC), one of the commonly used antibiotics, was explored by using novel photocatalysts of rGO/Ag₂CO₃ under simulated sunlight, because conventional treatment methods are not efficient on the removal of TC. rGO/Ag₂CO₃ nanocomposites were synthesized via a facile photo-ultrasonic assisted reduction method. More than 90% of TC was removed by 1% (weight_rGO/weight_composites) rGO/Ag₂CO₃ within 60 min at pH = 4, which was about 1.3 times higher than that of pure Ag₂CO₃. The cycling experiments indicated that 1% rGO/Ag₂CO₃ was highly stable and could be reused for at least 5 cycles without significant deactivation to its photocatalytic activity. In addition, the effects of pH, temperature, and dosage amount of 1% rGO/Ag₂CO₃ on photocatalytic degradation were investigated. Meanwhile, the effect of ultrasonic on the degradation of TC was also investigated. This study can provide a new method for the preparation of smaller nanosized materials and photocatalysts with high activity and stability for its environmental or other applications.

Band gap engineering of BiOI via oxygen vacancies induced by graphene for improved photocatalysis

A reduced graphene oxide–bismuth iodide oxide (rGO–BiOI) composite was prepared by a thermal reduction method.

pH-Dependent photocatalytic performance of modified bismuth vanadate by bismuth ferrite

The photoelectrochemical performance of bismuth vanadate (BVO) improved by a thin layer of bismuth ferrite (BFO).