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Expanding the optical absorption range of photocatalysts is still a key endeavor in graphitic carbon nitride (g-C3N4) studies. Here, we report on a novel thiophene group extending the optical property, which is assigned to n-π* electronic transitions involving the two lone pairs on sulfur (TLPS). The as-prepared samples, denoted as CN-ThAx (where x indicates the amount of ThA added, mg), showed an additional absorption above 500 nm as compared to pristine g-C3N4. Further, the thiophene group enhanced charge carrier separation to suppress e−/h+ pair recombination. The experimental results suggest that the thiophene group can obstruct the polymerization of melem to generate a large plane, thus exposing the lone electron pairs on the sulfur. The photocatalytic activity was evaluated in the decomposition of bisphenol A and H2 evolution. Compared with g-C3N4, the optimized CN-ThA30 sample led to a 6.6- and 2-fold enhancement of the degradation and H2 generation rates, respectively. The CN-ThA30 sample allowed for synchronous H2 production and BPA decomposition.

Intimate understanding of the synthesis-structure–activity relationships is an accessible pathway to overcome the intrinsic challenges of carbon nitride (g-C3N4) photocatalysts. This work looks in the effects of humidity of the synthesis process to the morphology, chemical structure, band structure as well as the photocatalytic activity of g-C3N4 materials. Four g-C3N4 samples were prepared by heating melem in four gas environments: dry Ar, dry Air, moist Ar and moist Air. The photocatalytic activity measurements revealed that the samples synthesized in moist inert and oxidic gases environments displayed 20 and 10 times the photocatalytic H2 evolution activity of the samples synthesized in dry inert and oxidic gases environments, respectively. The reasons for this remarkable variety in photocatalytic activities had been through investigated. After all, the terminations of the carbon vacancies were identified as the dominant factor in enhancing H2 evolution performance. The work here thus demonstrating an example of defect engineering.

A sustainable bio-based future necessitates the utilization of all components of biomass including lignin, which is the second most abundant biopolymer and a source of renewable aromatics. While its use for low value fuel and power production is well established, deriving further value from it via various conversion and upgrading schemes can help enable economically and environmentally sustainable and profitable biorefineries and provide opportunities to implement the principles of Green Chemistry to minimize negative environmental impacts. As lignin is converted to phenolic monomers, dimers, and oligomers via various conversion methods, electrocatalytic upgrading of these lignin-derived intermediates offers a sustainable way to integrate renewable energy sources such as wind and solar with biomass conversion methods to make valuable products. Using this strategy, abundant low-value lignin intermediates can be used to capture excess renewable electricity in the form of chemical bonds. Furthermore, this process allows for fine tuning of selectivity via the control of electrical potential and avoids elevated temperatures and pressures, further reducing energy inputs. Herein, we present a review of recent electrochemical studies of lignin-derived model compounds. Both oxidative and reductive methods for electrocatalytic upgrading of lignin-relevant monomers are discussed as well as electrocatalytic cleavage of lignin dimers representing specific linkages. Towards framing this technology's future implementation, we also provide a perspective on the main challenges and opportunities in this growing field.

Novel LED-light-active N-doped BiOIO3 was synthesized successfully by calcination treatment of the mixture of BiOIO3 and urea. It gave a fairly easy way to coordinate the control of bandgap engineering. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed the incorporation of nitrogen into the BiOIO3. In UV–vis diffuse reflection spectroscopy (UV–vis), photocurrent-time measurement (PT) and electrochemical impedance spectroscopy (EIS), the N-doped BiOIO3 exhibits enhanced visible-light absorption and improved photocurrent response compared to pure-BiOIO3. The photocatalytic activity of the samples was evaluated via photodegradation of rhodamine B (RhB), bisphenol A (BPA), tetracycline (TC) and ciprofloxacin (CIP) under LED light irradiation. The N-doped BiOIO3 showed higher photocatalytic activity than pure BiOIO3.

A one-step calcination method was designed to synthesize Fe-doped surface-alkalinized graphitic carbon nitride (g-C3N4). Results of transmission electronmicroscope (TEM) and elemental mapping, X-ray photoelectron spectroscopy (XPS) indicated that the Fe species might exist between layers in g-C3N4. From the photoluminescence (PL) and transient photocurrent response results, doping trace amounts of Fe could accelerate the separation of photo-generated carriers, and further increase the generation of active species. Among various photocatalysts, the composite (0.05 wt% Fe) exerts maximum photocatalytic performance in the degradation of tetracycline (TC) under visible-light irradiation. A very low Fe species content of 0.05% resulted in a 3 fold higher reaction rate than that of bulk g-C3N4. In addition, the as-synthesized materials exhibited efficient and stable visible light driven photodegradation activity in degradation of TC, which could be used as a candidate for application eliminating antibiotics in the environment.

This research was designed to synthesize a magnetic in situ Fenton-like photocatalyst using simple methods. The sheet materials of BaFe12O19, with inherent magnetic properties, decorated with Ag3PO4 and in situ catalytic conversion of H2O2 generated on the surface of Ag3PO4 could produce more reactive oxygen species (ROS) for degradation of organic pollutants via a photo-Fenton process. ESR, trapping experiments of different scavengers and H2O2 detection proved that the ROS of oxidation of bisphenol A is mainly produced by the Fenton-like reaction. This work has effectively improved the degradation activity of Ag3PO4. Simultaneously, the BaFe12O19/Ag3PO4 composite can be easily separated from the reaction system via applying an external magnetic field, and shows promising applications for the photo-oxidative degradation of environmental contaminants.

g-C3N4/BiOI composites with different ratios were prepared by in-situ generation route at room temperature and applied in antibacterial investigation. Detailed information of the composites was characterized by XRD, TEM, HRTEM, SEM, EDS, BET, XPS, FT–IR, UV–Vis, photocurrent and EIS. The obtained g-C3N4/BiOI composites presented excellent antibacterial performance toward Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under LED track light, with the complete inactivation of bacterial within 30 min. The decomposition of bacterial cells was observed by SEM. The bacterial mechanism was investigated by trapping experiments: holes (h+), superoxide anion free radical (O2−) and hydrogen peroxide (H2O2) were identified as active species for bacterial inactivation, and h+ had a main effect in the antibacterial process. The enhanced photocatalytic activities were assigned to an efficient separation and transition of electrons (e−) and h+ in photocatalytic antibacterial process. This work indicated the g-C3N4/BiOI composites are promising photocatalytic antibacterial materials for water disinfection.

A high-performance photocatalyst should be superior not only in light absorption and charge transfer but also surface catalytic reaction. Here we report a green and simple strategy for evenly decorating Ag3PO4 particles using magnetic NiFe2O4 nanoparticles (NPs). The NiFe2O4 NPs could act as a magnetic support material for recycling the photocatalysts, as well as in situ catalytically decompose the H2O2 produced on the surface of Ag3PO4 into O2 − and OH radicals via a photo-Fenton process. The catalytic decomposition of H2O2 could produce strong oxidative capacity O2 − and OH radicals for the organic pollutants degradation and reduce host semiconductor holes ( h + ( A g 3 P O 4 ) ) consumption by these produced H2O2. Thus, the photocatalytic activities of Ag3PO4@NiFe2O4 composites were greatly enhanced. Taking the photocatalytic degradation of Methyl orange (MO), hardly decomposed colorless phenol compounds bisphenol A (BPA) and killing Escherichia coli (E. coli) as mode photocatalytic reactions, this system exhibited superior photocatalytic performances than that of pristine Ag3PO4. Electron spin resonance (ESR) spectroscopy and sacrificial-reagent incorporated photocatalytic characterizations indicated that the in situ eliminating/active decomposition of H2O2 produced by Ag3PO4 was the main reason for the enhanced photocatalytic activities.

Novel 3D flower-like Ag2S/SnS2 composites were fabricated by a hydrothermal and ion exchange method. Uniform Ag2S quantum dots were homogeneously interspersed on 3D flower-like SnS2. The samples were characterized through X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) analysis. As expected, the as-prepared Ag2S quantum dot modified 3D flower-like SnS2 composites exhibited enhanced photoelectrochemical (PEC) performance and photocatalytic activities. The photocurrent density of 3% 3D flower-like Ag2S/SnS2 at 2.0 V (vs. Ag/AgCl) (0.65 mA cm−2) was about 3.25 times higher than that (0.2 mA cm−2) of 3D flower-like SnS2. The photocatalytic activity of 3D flower-like Ag2S/SnS2 composites was assessed through the degradation of methyl orange and the photocatalytic H2 evolution performance under visible light irradiation. The coupling of SnS2 and Ag2S quantum dots could notably promote the photocatalytic activity. The experimental results indicated that 3% 3D flower-like Ag2S/SnS2 composites showed the best photocatalytic performance for the degradation of methyl orange. These composites also exhibited a high H2 evolution rate of 574.7 μmol h−1 g−1 under visible light irradiation, approximately 5.57 times higher than that of pure 3D flower-like SnS2. Based on the calculation, radical trapping tests and ESR, a plausible mechanism for increased photoactivity was proposed. This work provides experimental insight into the design of low-cost photocatalysts for highly efficient photodegradation and photocatalytic H2-production.

In this work, a novel Ag 3 PO 4 @CoFe 2 O 4 composite photocatalyst was synthesized via a phosphate salts alkalinity adjustment strategy. Structure, morphology, and chemical component analysis indicated that the magnetic CoFe 2 O 4 nanoparticles (NPs) were evenly decorated on the surface of Ag 3 PO 4 particles, forming a sesame ball like structure. This unique structure ensures that the Ag 3 PO 4 @CoFe 2 O 4 composites could be totally separated by the magnet field. Photocatalytic water disinfection and organic pollutants degradation were employed to evaluate the photocatalytic performance of the as-prepared magnetic photocatalysts. The results showed that the optimum 3% Ag 3 PO 4 @CoFe 2 O 4 composite could completely inactivate 1*10 7 cfu/mL of Escherichia coli within 40 min, much faster than the pristine Ag 3 PO 4 . Meanwhile, the 3% Ag 3 PO 4 @CoFe 2 O 4 composite also showed a dramatic enhancement of photocatalytic activities for the organic pollutants degradation. The reactive oxygen species yield measurements, O 2 control photocurrents experiments, O 2 -TPD tests and photoluminescence spectra analysis indicate that the surface modification of CoFe 2 O 4 NPs could facilitate the O 2 adsorption and O O bond activation/cleavage/oxide removal and accelerate the two-electron oxygen reduction reaction for H 2 O 2 generation on the surface of Ag 3 PO 4 , and thus more ROSs were generated. In addition, due to the acceleration of electrons consumption, more holes will be left for the organic pollutants oxidation, and the photocatalytic activities as well as stability of Ag 3 PO 4 therefore have been greatly improved.

A novel visible-light driven ZnFe 2 O 4 /Ag/Ag 3 VO 4 photocatalyst was successfully fabricated through a two-step hydrothermal method. The structure, morphology and composition of the samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photo-electron spectroscopy (XPS). The as-prepared ZnFe 2 O 4 /Ag/Ag 3 VO 4 composites possessed an excellent performance in the photocatalytic degradation of methyl orange and tetracycline under visible-light irradiation. The results of electrochemical impedance spectroscopy (EIS) indicated that the ZnFe 2 O 4 /Ag/Ag 3 VO 4 composite could facilitate the separation of photo-generated carriers, as well as accelerated charge transfer. The 5% ZnFe 2 O 4 /Ag/Ag 3 VO 4 composite exhibited the upmost photocatalytic activity, the degradation constant of 5% ZnFe 2 O 4 /Ag/Ag 3 VO 4 is as high as 1.49 times to that of Ag/Ag 3 VO 4 . Also, according to the trapping experiments, it’s found that the superoxide radicals ( O 2 − ) and hole (h + ) were the predominant reactive species in this system. The ZnFe 2 O 4 /Ag/Ag 3 VO 4 photocatalyst is promising for designing as an environmental purification material in treatment of antibiotic pollutant.

Dark orange montmorillonite/g-C3N4 composites were prepared through a conventional calcination route. The obtained samples were analyzed by XRD, TEM, TG, XPS, FT-IR, DRS, Photocurrent-time and PL measurements. The photocatalytic performance of montmorillonite/g-C3N4 composites was assessed by the methylene blue (MB) degradation. Compared to pure g-C3N4, the obtained photocatalysts displayed outstanding photocatalytic activity. The improved photocatalytic activity was ascribed to the improved absorbance in the visible light range and favorable adsorptive capacity to MB dye. The electron spin resonance (ESR) analysis and trapping experiment showed that •O2− and h+ played a major role in the decomposition of MB. In addition, it was found that montmorillonite/g-C3N4 (0.5) composite had a new property, which showed that it can be applied as a sensor in the photoelectrochemical detection of trace amount of Cu2+.

In order to construct a magnetic recyclable photocatalyst with superior photocatalytic performance and stability, Ag/AgBr photocatalysts modified by magnetic CoFe2O4 nanoparticles (NPs) were synthesized via deposition–precipitation followed by a solvothermal process. Such a synthesis strategy allows the even dispersion of CoFe2O4 NPs on the surface of Ag/AgBr. Besides, a Z-scheme photocatalyst with metallic Ag as a solid-state electron mediator was formed, which exhibits excellent photocatalytic activity and stability for photocatalytic degradation of hardly decomposed colorless phenol compounds, namely, endocrine disrupting chemical bisphenol A (BPA) and 4-chlorophenol (4-CP), in an aqueous solution. The results showed that the Ag/AgBr@CoFe2O4 composites not only exhibited enhanced photocatalytic performance but also improved stabilities. More importantly, the photocatalysts could be recycled easily by an external magnetic field. The antibacterial activity of the Ag/AgBr@CoFe2O4 composites have been investigated by eliminating Escherichia coli (E. coli) in water under visible light irradiation, and the results revealed that the Ag/AgBr@CoFe2O4 composites possessed good photocatalytic antibacterial activity. At last, the enhanced photocatalytic mechanisms were discussed by investigating the main reactive species in the photocatalytic process, which revealed that the photo-generated holes (h+) and O2˙− were the main reactive species.

Recently, nano/micro-scale Fe-based ferrites with high electrochemical performances have attracted extensive attention. However, almost all the mixed Fe-based oxide research paid close attention to the crystalline phase, despite the low-crystalline or amorphous phase possessing excellent electrochemical performance. Herein, a low-crystalline mesoporous cobalt ferrite and carbon composite (L-CoFe2O4/C) material with high surface area and superior electrical conductivity was prepared via a simple citric acid assisted sol–gel approach and calcination process. The L-CoFe2O4/C electrode exhibits an unprecedented specific capacitance (600 F g−1 at 1 A g−1), which precedes some of the reported mixed Fe-based ferrite electrodes and their crystalline counterparts. The excellent electrochemical performance can mainly be attributed to the sufficient diffusion and reaction of electrolyte ions, more surface defects (e.g. oxygen vacancies) for redox reactions, and the predominant electro-conductivity of the composite during the charging/discharging process. Moreover, an L-CoFe2O4/C-based asymmetric supercapacitor exhibited high energy density and power density, and outperformed most of the reported mixed Fe-based symmetric and asymmetric supercapacitors. These findings promote new opportunities for low-crystalline Fe-based metal oxides as high performance energy storage devices.

Two methods were studied for selectively measuring the on-chip absorbance of trace sulfate analytes in droplets on a digital microfluidics (DMF) platform. In one method, the direction of measurement was perpendicular to the flat upper and lower surfaces of the DMF platform (vertical), and in the second method, the measurement direction was parallel to the DMF platform surfaces (horizontal). The channel height or the vertical light path length was 0.24 mm, and the droplet diameter was 1 mm. The DMF system employed a silicone oil transport medium whereby a thin, non-uniform oil layer formed between the droplet and the upper/lower plates which was unstable, resulting in randomly formed local oil lenses. The mobile oil lenses caused vertical absorbance measurement errors and uncertainties. The effects of the oil lenses were verified by simulation. Horizontal absorbance measurements were taken with embedded optical fibers (0.2 mm in diameter) aligned over the bottom chip surface in contact with the sides of the droplet, resulting in a horizontal light path length approximately three times that of the vertical light path. Because no oil lenses could form on the droplet’s sides, the stability of repeated horizontal measurements outperformed repeated vertical measurements made on the same droplet and on multiple droplets actuated into the measurement positions. Comparisons were based on measurement standard deviations and limits of detection (LOD). The following LODs and measurement standard deviations were achieved for horizontal measurements of multiple sulfate concentrations in 1.5 µl droplets: 7 ppm for sulfate (0.3–2.7%) and an R2 value of 0.957 from a least square data fit. Measurements on a commercial plate reader gave comparable results (200 µl liquid in each well, LOD equals 11 ppm, CV equals to 0.2–4%), even though the absorbance path was larger (0.7 mm). This LOD value means that the chip could detect 10.5 ng of sulfate. LOD values on vertical measurements were also similar, but large measurement errors from numerous outlier points yielded an R2 value of 0.735 and large average measurement standard deviations (36%).

Light absorption and carrier transfer, are two sequential and complementary steps related to photocatalysis performance, whereas the collective integration of these two aspects into graphitic carbon nitride (g-C3N4) photocatalyst through polycondensation optimization have seldom been achieved. Herein, we report on tailoring the crystalline structure of g-C3N4 by avoiding the formation of incompletely reacted N-rich intermediates and selective breaking the hydrogen bonds between the layers of g-C3N4 simultaneously. The obtained layer plane ordered porous carbon nitride (LOP-CN) material shows efficient photocatalytic H2 generation performance. The highest H2 evolution rate achieved is 53.8 μmol under λ ≥ 400 nm light irradiation, which is 7.4 times higher than that of g-C3N4 prepared by convention thermal polycondensation. The substantially boosted photocatalytic activity is mainly ascribed to the efficient charge separation on long-range atomic order layer plane and the extended visible light harvesting ability. This work highlights the importance of crystalline structure tailoring in improving charge separation and light absorption of g-C3N4 photocatalyst for boosting its photocatalytic H2 evolution activity.

For this study, ionic liquid-modified carbon nitride (hm-CN) was one-step synthesized by 1-butyl-3-methylimidazolium cyanamide and carbon nitride (g-C3N4). After the addition of ionic liquids, the structural change of hm-CN increases the separation of photogenerated electron holes and improves the photocatalytic performance. The colorless pollutant bisphenol A (BPA) is degraded as the target pollutant under the visible light irradiation. The catalytic performance of g-C3N4 modified by ionic liquid is better than pure g-C3N4. The best performance is 30hm-CN, which degrades 95% of the pollutants in 3 hours. Its degradation performance is 4.5 times that of pure g-C3N4 and the degradation performance is still excellent after three cycles. According to electron spin resonance (ESR) and trapping experiments, h+ and •O2− play a key role in the photocatalytic degradation process. In addition, we conducted a series of condition experiments to perform degradation under different catalyst concentrations, different ions and different pH to fully understand the impact of external interference on the catalyst. At the same time, the sample also has good activity in degrading other pollutants (Rhodamine B, Methylene blue, Tetracycline, Ciprofloxacin). This study simply designed a method to synthesize ionic liquid modified g-C3N4 for improving photocatalytic performance, and provided a new idea for the research of carbon nitride modification at the same time.

Visible-light-driven magnetic CoFe2O4/Ag/Ag3VO4 photocatalysts with different weight ratios of CoFe2O4 were successfully synthesized by a hydrothermal method. The as-prepared samples have been characterized by X-ray diffraction (XRD), infrared (IR), scanning electron microscopy with an energy-dispersive X-ray spectroscope (SEM-EDS), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Ultraviolet–visible absorption spectroscopy (UV–vis) and vibrating sample magnetometer (VSM). The photocatalytic experiments indicate that the CoFe2O4/Ag/Ag3VO4 composites possess enhanced visible-light-driven photocatalytic activity towards the degradation of methyl orange (MO), tetracycline (TC) and killing Escherichia coli (E. coli). Electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) spectra analysis indicate that the introduction of CoFe2O4 could efficiently promote the separation efficiency of photogenerated charge carriers in Ag/Ag3VO4. It is obvious that the composites show better photocatalytic activity than the pure Ag/Ag3VO4 and CoFe2O4. In particular, the 5% CoFe2O4/Ag/Ag3VO4 sample shows the highest photocatalytic activity and the degradation constant of 5% CoFe2O4/Ag/Ag3VO4 is as high as 3.4 times to that of Ag/Ag3VO4. The trapping experiments show that O2− and h+ are the major reactive species for the CoFe2O4/Ag/Ag3VO4 photocatalytic system. In addition, the as-prepared CoFe2O4/Ag/Ag3VO4 composite can be quickly separated from the solution by an extra magnetic field after the photocatalytic reaction. The cyclic test and the XRD patterns before and after cyclic test show that the CoFe2O4/Ag/Ag3VO4 hybrid materials have the stable degradation ability and crystal structure during the photodegradation process. Furthermore, it shows highly efficient visible light photocatalytic antibacterial activity. In all, the CoFe2O4/Ag/Ag3VO4 photocatalyst, as the magnetic photocatalyst and antibacterial, is promising for the further practical application of photocatalysis in wastewater treatment.

A novel ternary composite photocatalyst (g-C3N4/BiOI/BiOBr) was prepared via a facile solvothermal method. The samples were characterized by powder X-ray diffraction, transmission electron microscopy, UV-visible diffuse reflection spectrometry, X-ray photoelectron spectrometry and photoluminescence measurements. Under irradiation with visible light, the g-C3N4/BiOI/BiOBr photocatalyst showed a higher photocatalytic activity than pure g-C3N4 and BiOI/BiOBr for the degradation of methylene blue. Among the hybrid photocatalysts, 3% g-C3N4/BiOI/BiOBr showed the highest photocatalytic activity for the degradation of MB. These results suggest that the heterostructure combination of g-C3N4, BiOI and BiOBr provides a synergistic effect through an efficient charge transfer process.

Core–shell magnetic Ag/AgCl@Fe2O3 photocatalysts were synthesized using a two-step method. The introduced Fe2O3 can be effectively dispersed on the surface of the Ag/AgCl. The Fe2O3 on the surface can act as a shell to prevent the inactivation of the inner Ag/AgCl by bisphenol A (BPA). The composites were investigated by XRD, SEM-EDS, XPS, UV-vis, VSM, and so on, which confirmed that the core–shell magnetic Ag/AgCl@Fe2O3 was successfully obtained. The EIS and PL results suggest that the composite has better electron–hole separation ability, which is beneficial for enhancing the photoactivity. The degradation of the BPA solution results show that the 5% Ag/AgCl@Fe2O3 has the highest photoactivity, the degradation rate of which is as high as about 13 times that of pure Ag/AgCl. Besides, the composites still have much better degradation ability than the pure Ag/AgCl in each cycle experiment. The photocatalytic antibacterial experiment showed that the composite could completely kill the pathogenic microorganism E. coli under visible light irradiation at 30 min. The results suggest that the core–shell magnetic Ag/AgCl@Fe2O3 can be used as an effective magnetic recyclable photocatalyst in eliminating the colorless pollutant bisphenol A and microbial contamination. Furthermore, a possible reaction mechanism was proposed based on the trapping experiments and the ESR results.

Introducing a built-in electric field (BIEF) has been considered a promising strategy to separate photoinduced electron/hole pairs and to boost the photocatalytic performance of semiconductor photocatalysts. In this work, an amorphous carbon component was formed in-situ and modified on the surface of graphitic carbon nitride (g-C3N4) by copolymerization via a simple green method, in which the amorphous carbon could adjust the band structure and form a BIEF. A variety of measurements, such as X-ray photoelectron spectroscopy (XPS), Mott-Schottky plots and density functional theory calculations, revealed that the BIEF could adjust the intrinsic electronic state and promote photoinduced electron delocalization for the effective separation of carriers in the region, thereby boosting photoelectron transport and improving the reaction kinetics. As a result, the highly photocatalytic activity of CN-PhA30 was demonstrated by degrading bisphenol A (BPA), and the efficiency reached 100 % after 80 minutes of irradiation—a rate that was more than 13 times that of pure g-C3N4. It is worth mentioning that CN-PhA30 also exhibited higher photocatalytic activities for H2 generation and antibiotic degradation. The results showed that the enhanced photocatalytic performance could be attributed to the directional transfer of electrons due to the BIEF formed by amorphous carbon on the surface of g-C3N4.

Antibiotics in natural waters have posed serious threats to our ecosystem due to its potent biological toxicity. In the present work, a visible-light-driven PANI/Bi4O5Br2 composite photocatalyst was fabricated and used for the degradation of ciprofloxacin (CIP) and tetracycline (TC) antibiotics under visible light (λ ＞ 420 nm). The PANI/Bi4O5Br2 composite presented a significantly improved ability of CIP and TC photodegradation, which is about 2.2 times and 1.6 times to that of Bi4O5Br2, respectively. The promoted photocatalytic activity results from the interface interaction between PANI and Bi4O5Br2, which contributes to the electron-hole separation. The degradation process of CIP was monitored by mass spectrometry, and a possible degradation pathway was proposed based on the analysis of the product. A microbiological antibacterial experiment was designed, proving that the degraded products of CIP and TC have lower toxicity. Furthermore, long wavelength light irradiated (λ ＞ 550 nm) experiment indicated that the introduction of PANI helps to extend the light absorption region and use the long wavelength light more efficiently, thereby promoting the photocatalytic ability. The optimal composite applied for TC degradation was 0.1% PANI/Bi4O5Br2. Its reaction rate constant was 2.8 times to that of Bi4O5Br2 (λ ＞ 550 nm). Eventually, a possible photocatalytic mechanism over PANI/Bi4O5Br2 composite was proposed.

ZnFe2O4/AgI composites were first prepared successfully with a hydrothermal method, and ZnFe2O4 nanoparticles were uniformly decorated on the surface of AgI particles. The photocatalytic activities of the obtained ZnFe2O4/AgI composites were investigated by the degradation of organic pollutants and the inactivation of bacteria under visible light irradiation. The results showed that the introduction of ZnFe2O4 greatly enhanced the light harvesting ability and improved the separation efficiency of the photogenerated charge carriers, which contributed to the enhanced generation of reactive species and thus promoted the photocatalytic performance. The 5% ZnFe2O4/AgI composite exhibited the optimal photocatalytic disinfection of E. coli (100% removal efficiency in 80 min) as well as the photocatalytic degradation of rhodamine B (RhB) (98.5% removal rate in 40 min). Furthermore, four consecutive cycles also demonstrated the stable photocatalytic activity of the as-prepared ZnFe2O4/AgI composites. In addition, H2O2 was identified as the predominant active species in the photocatalytic inactivation of bacteria. This study indicated that ZnFe2O4/AgI composites are a promising candidate for the treatment of wastewater.

A magnetic photocatalytic CoFe2O4/g-C3N4 composite was successfully synthesized by a simple calcination method. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared (IR) spectra, UV–Vis diffuse reflection spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS) were applied to characterize the as-prepared samples. The magnetic properties of CoFe2O4 and CoFe2O4/g-C3N4 composites were measured by using a vibrating sample magnetometer (VSM) at room temperature. Photocatalytic property of the CoFe2O4/g-C3N4 composite was assessed by degrading methylene blue (MB) in aqueous medium under visible light irradiation. The results showed that the composite of 41.4% CoFe2O4/g-C3N4 exhibited the highest photocatalytic activity. It could activate H2O2 to degrade MB up to 97.3% in 3 h under the visible light irradiation. This enhancement could be attributed to the synergistic effect between CoFe2O4 and g-C3N4, which could enhance their activity of activating H2O2 to degrade MB under visible light. The CoFe2O4/g-C3N4 composites also have a strong magnetic ability. After the photocatalytic reaction, it can be quickly separated from the water by an extra magnetic field. Moreover, a possible photocatalytic mechanism was proposed.

Nano-size g-C3N4 derivatives were fabricated by a simple dissolve-regrowth method in HNO3 solution followed by a calcination process. X-ray diffraction (XRD), Z-potential, elemental analysis and IR are used to investigate the structure, composition and the properties of the samples. Scanning electron microscopy (SEM) shows the average size of the nano-size g-C3N4 derivatives increases with increasing calcination temperature. Methyl orange (MO) dye was used as the target pollutant to investigate the photoactivity of the samples. The pure g-C3N4 can only degrade about 1.1% MO, while the g-C3N4 derivatives calcined at 300 °C can decompose about 31.9% of MO in 4 h. Besides, when a small amount of methylene blue (MB) solution was introduced, the g-C3N4–HNO3-300 can decompose about 75.8% in 4 h. The photoactivity of g-C3N4 was greatly enhanced after the modification process (especially with the assistance of MB). Additionally, this work supplied a simple method to modify materials with enhanced photoactivity. Finally, the possible reactive species and the possible mechanism were proposed based on Electron spin resonance (ESR) and XPS results.

A core–shell structured magnetic Ag/AgBr@Fe2O3 composite was synthesized through a facile solvothermal method. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible absorption spectroscopy (UV-vis) were applied to characterize the structures and properties of the as-prepared samples. The results indicate that Fe2O3 was coated on the surface of Ag/AgBr and heterostructures were formed. Electrochemistry analysis and photoluminescence (PL) spectra analysis indicate that the introduction of Fe2O3 could improve electron and hole separation efficiency. The photocatalytic activity of the Ag/AgBr@Fe2O3 composites was evaluated by using organic dye methyl orange (MO), endocrine disrupting chemical bisphenol A (BPA) and Escherichia coli (E. coli) as the target pollutants. The as-prepared Ag/AgBr@Fe2O3 composites exhibited much higher photocatalytic activities than pure Ag/AgBr, which was attributed to the effective charge separation of the Ag/AgBr@Fe2O3 composite. In addition, the as-prepared Ag/AgBr@Fe2O3 composite has magnetic properties, therefore after the photocatalytic reaction, it can be quickly separated from solution by an extra magnetic field. Trapping experiments and ESR analysis indicate that the h+ and ˙O2− are the main active species for the photocatalytic degradation. A possible Z-scheme pathway photocatalytic mechanism was proposed.

Novel plasmonic photocatalysts, Ag/AgCl/CoFe2O4, were prepared via a two-step synthesis method. The obtained Ag/AgCl/CoFe2O4 composites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible absorption spectroscopy (UV-vis). The magnetic properties of the samples were studied by vibrating sample magnetometer (VSM) analysis. Methyl orange (MO), bisphenol A (BPA) and ciprofloxacin (CIP) were used as target pollutants to investigate the degradation capability of Ag/AgCl/CoFe2O4. Results showed that the composite can degrade both colored and colorless pollutants, while Ag/AgCl/CoFe2O4 (3 : 1) composite showed the highest photoactivity in the degradation of MO. It can degrade about 93.38% MO in 1.5 h. The reactive species scavenger results indicated that hydroxyl radicals (˙OH) were not the main photooxidant, while holes (h+) and superoxide anion radicals (˙O2−) played key roles in MO decoloration. Furthermore, the degraded solution of BPA was analyzed using high performance liquid chromatography (HPLC). The results showed that BPA was decomposed gradually. The composite was magnetically separated and investigated using three successive recycle experiments under visible light. The results exhibited that the photoactivity of Ag/AgCl/CoFe2O4 is stable. Besides, Ag/AgCl/CoFe2O4 also exhibited good antibacterial activity against Escherichia coli (E. coli). The method used to prepare the composite can be expanded and applied to synthesize other magnetically separable photocatalysts.

A two-step method was developed to prepare magnetic separable Fe2O3/g-C3N4 photocatalysts. The samples were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible absorption spectroscopy (UV-vis), photoluminescence (PL) spectroscopy and X-ray photoelectron spectroscopy (XPS). The magnetic capability of the samples was investigated by vibrating sample magnetometer (VSM) analysis. The crystal phase and the magnetic property of the Fe2O3 can be tuned by changing the calcination temperature. The Fe2O3/g-C3N4 photocatalyst showed enhanced photoactivity in degrading the rhodamine B (RhB) dye. Among the samples, the 10% Fe2O3/g-C3N4 showed the highest photocatalytic activity. It can degrade about 96.7% RhB in 4 h. The photocurrent results confirm that the combination of the two materials is beneficial for the separation of electron–hole pairs. The electron spin resonance (ESR) results indicates that ˙O2− and ˙OH are the main active species in the degradation process.

The Ag/AgCl/g-C 3 N 4 composites were prepared by in situ oxidation process. During the process, the prefabricated Ag nanoparticles well dispersed on the surface of g-C 3 N 4 employed as a template and oxidized by FeCl 3 to form the Ag/AgCl core–shell structure. The resultant samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (IR) spectroscopy and UV–vis diffuse-reflection spectra (DRS). As a kind of visible-light-driven plasmonic photocatalysts, the Ag/AgCl/g-C 3 N 4 with the Ag/AgCl amount of 2.7 at% achieved the best photocatalytic activity for the methyl orange (MO) dye degradation. The photocatalytic degradation rate was 6.77 and 6.27 times as that of the g-C 3 N 4 and Ag/g-C 3 N 4 composites. The results indicated that the cooperative or synergistic effects between Ag/AgCl and g-C 3 N 4 was existed which facilitated the separation of photo-induced electron–hole pairs and enhanced the photoactivity. Based on the results, a possible visible-light photocatalytic degradation mechanism was also discussed.