Insight into the adsorption and photocatalytic properties of in-situ synthesized g-C3N4/SnS2 nanocomposite

In this paper, a novel g-C₃N₄/2 wt% SnS₂ nanocomposite was successfully synthesized using an in-situ growth of SnS₂ on g-C₃N₄. X-ray diffraction (XRD), atomic force microscopy (AFM), Brunauer-Emmett-Teller (BET) method, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectrometer were used to characterize the photocatalysts. Exploring adsorption behavior, as an importatnt stage during photocatalytic reactions, is of great importance. Hence, both adsorption and photocatalytic performance of the synthesized photocatalysts have been investigated in detail. The adsorption isotherm fittings exhibited that Freundlich and Langmuir-Freundlich models can be applied to the methylene blue (MB) adsorption on the photocatalysts, indicating surface heterogeneity should be considered. A pseudo-second-order model was fitted to explore the adsorption kinetics. According to the observed redshift in the Fourier transform infrared spectroscopy (FTIR) result of g-C₃N₄/SnS₂ nanocomposite, π-π interaction was dominant during MB adsorption. Also, a slight redshift and significant PL intensity reduction in g-C₃N₄/SnS₂ nanocomposite led to 96% photocatalytic efficiency after 180 min under visible light radiation. The kinetics of photodegradation over g-C₃N₄/SnS₂ was about 9 and 3 times higher than those of g-C₃N₄ and SnS₂ photocatalysts, respectively. The superoxide and hydroxyl radicals were the main reactive species in the photocatalytic degradation with a Z-scheme charge transfer mechanism. The g-C₃N₄/SnS₂ nanocomposite was found to be remarkably stable after three consecutive cycles of MB degradation.     

Novel spindle-shaped nanoporous TiO2 coupled graphitic g-C3N4 nanosheets with enhanced visible-light photocatalytic activity

Highly efficient visible-light-driven heterojunction photocatalysts, spindle-shaped nanoporous TiO₂ coupled with graphitic g-C₃N₄ nanosheets have been synthesized by a facile one-step solvothermal method. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption analysis and UV–vis diffuse reflectance spectrometry (DRS), proving a successful modification of TiO₂ with g-C₃N₄. The results showed spindle-shaped nanoporous TiO₂ microspheres with a uniform diameter of about 200 nm dispersed uniformly on the surface of graphitic g-C₃N₄ nanosheets. The g-C₃N₄/TiO₂ hybrid materials exhibited higher photocatalytic activity than either pure g-C₃N₄ or nanoporous TiO₂ towards degradation of typical rhodamine B (RhB), methyl blue (MB) and methyl orange (MO) dyes under visible light (>420 nm), which can be largely ascribed to the increased light absorption, larger BET surface area and higher efficient separation of photogenerated electron–hole pairs due to the formation of heterostructure. In addition, the possible transferred and separated behavior of electron–hole pairs and photocatalytic mechanisms on basis of the experimental results are also proposed in detail.     

Facile synthesis of WO3 nanorods/g-C3N4 composites with enhanced photocatalytic activity

In this paper, WO₃ nanorods (NRs)/g-C₃N₄ composite photocatalysts were constructed by assembling WO₃ NRs with sheet-like g-C₃N₄. The as-synthesized photocatalysts were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy and photoluminescence. The photocatalytic activity of the photocatalysts was evaluated by degradation of Rhodamine B (RhB) under simulated sunlight irradiation. Compared to pristine WO₃ NRs and g-C₃N₄, WO₃ NRs/g-C₃N₄ composites exhibit greatly enhanced photocatalytic activities. The enhanced performance of WO₃ NRs/g-C₃N₄ composite photocatalysts was mainly ascribed to the synergistic effect between WO₃ NRs and g-C₃N₄, which improved the photogenerated carrier separation. A possible degradation mechanism of RhB over the WO₃ NRs/g-C₃N₄ composite photocatalysts was proposed.     

Facile one-step synthesis of pellet-press-assisted saddle-curl-edge-like g-C3N4 nanosheets for improved visible-light photocatalytic activity

Graphitic carbon nitride (g-C₃N₄) has attracted increasing interest as a visible-light-active photocatalyst. In this study, saddle-curl-edge-like g-C₃N₄ nanosheets were prepared using a pellet presser (referred to as g-CN P nanosheets). Urea was used as the precursor for the preparation of g-C₃N₄. Thermal polymerization of urea in a pellet form significantly affected the properties of g-C₃N₄. Systematic investigations were performed, and the results for the modified g-C₃N₄ nanosheets are presented herein. These results were compared with those for pristine g-C₃N₄ to identify the factors that affected the fundamental properties. X-ray diffraction analysis and high-resolution transmission electron microscopy revealed a crystallinity improvement in the g-CN P nanosheets. Fourier-transform infrared spectroscopy provided clear information regarding the fundamental modes of g-C₃N₄, and X-ray photoelectron spectroscopy (XPS) peak-fitting investigations revealed the variations of C and N in detail. The light-harvesting property and separation efficiency of the photogenerated charge carriers were examined via optical absorption and photoluminescence studies. The valence band edge and conduction band edge potentials were calculated using XPS, and the results indicated a significant reduction in the bandgap for the g-CN P nanosheets. The Brunauer–Emmett–Teller surface area increased for the g-CN P nanosheets. The photocatalytic degradation performance of the g-CN P nanosheets was tested by applying a potential and using the classical dye Rhodamine B (RhB). The RhB dye solution was almost completely degraded within 28 min. The rate constant of the g-CN P nanosheets was increased by a factor of 3.8 compared with the pristine g-C₃N₄ nanosheets. The high crystallinity, enhanced light absorption, reduced bandgap, and increased surface area of the saddle-curl-edge-like morphology boosted the photocatalytic performance of the g-CN P nanosheets.     

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

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

One-Step Synthesis of g-C3N4 Nanosheets with Enhanced Photocatalytic Performance for Organic Pollutants Degradation Under Visible Light Irradiation

Graphitic carbon nitride (g-C₃N₄) has received much interest as a visible-light-driven photocatalyst for degrading pollutants such as organic dyes and antibiotics. However, g-C₃N₄ bulk activity could not meet expectations due to its rapid recombination of photogenerated electron–hole pairs and low specific surface area. In our study, melamine was thermally treated one-step in the presence of NH₄Cl to produce g-C₃N₄ nanosheets. The characterizations of surface morphology and optical properties of all g-C₃N₄ samples were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrum (XPS), transmission electron microscopy (TEM), and UV–visible diffuse reflectance spectroscopy. Compared to bulk g-C₃N₄, g-C₃N₄ nanosheets demonstrated excellent photocatalytic activities, with approximately 98% RhB removal after 210 min of visible light irradiation. Furthermore, the effect of catalyst dosage, pH, and RhB concentration on the removal percentage dye of g-C₃N₄ nanosheets was also investigated. h⁺ and ^?O₂^? species were demonstrated as the key reactive species for the RhB. Besides, ECN exposed a tetracycline degradation efficiency of 80.5% under visible-light irradiation for 210 min, which is higher than BCN (60.8%). The improved photocatalytic activity of g-C₃N₄ nanosheets is due to the restriction of the recombination of photogenerated electrons/hole pairs, as provided by photoluminescence spectra and Nyquist plot. As a result, our research may offer an effective approach to fabricating g-C₃N₄ nanosheets with high photocatalytic activity and high stability for environmental decontamination.

     

Investigation of g-C3N4/ZnAl2O4 and ZnO/ZnAl2O4 nanocomposites: From synthesis to photocatalytic activity of pollutant dye model

The fabrication of nanocomposite photocatalytsts with excellent photocatalytic activity is an important step in the improved degradation of organic dyes. A series of nanocomposite photocatalysts was synthesized with g-C₃N₄ and ZnO loading contents of 10, 20 and 30%. The nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS). The optical band gaps of g-C₃N₄, ZnO and ZnAl₂O₄ were about 2.79, 3.21 and 3.55 eV, respectively. Methylene blue (MB) was degraded over the prepared photocatalysts under UV irradiation. Photocatalytic activity was about 9.1 and 9.6 times higher, respectively, on 20%g-C₃N₄/ZnAl₂O₄ and 20%ZnO/ZnAl₂O₄ nanocomposite photocatalysts than on pure ZnAl₂O₄ spinel powders. Recycling experiments showed that 20%g-C₃N₄/ZnAl₂O₄ and 20%ZnO/ZnAl₂O₄ nanocomposite photocatalysts exhibited good stability after five cycles of use.     

BiOCl and TiO2 deposited on exfoliated ZnCr-LDH to enhance visible-light photocatalytic decolorization of Rhodamine B

A series of novel TiO₂-BiOCl-ZnCr-Ex composites for use as photocatalysts were synthesized via a facile solvothermal process using an exfoliated ZnCr-LDH (ZnCr-Ex) and depositing BiOCl and TiO₂ sequentially on the surface of ZnCr-Ex. The composites were characterized by XRD, TEM, SEM-EDS and UV–vis diffuse reflectance spectroscopy. In these composites, the BiOCl nanosheets were deposited first on the surfaces of ZnCr-Ex and then the TiO₂ nanoparticles were dispersed on the surface of BiOCl-ZnCr-Ex material as were seen from SEM and TEM analyses. The photocatalytic degradation of Rhodamine B (RhB) indicated that the TiO₂-BiOCl-ZnCr-Ex composite showed much higher visible-light photocatalytic activity for degradation of RhB than TiO₂ alone, BiOCl alone or the BiOCl-ZnCr-Ex by itself. The possible mechanisms of photocatalytic activity were discussed. Moreover, the present composite photocatalysts exhibited satisfactory re-usability for at least three cycles. Because of the facile synthesis process, higher photocatalytic activity under visible light irradiation and satisfactory re-usability of these composites, they can be touted as potential catalysts for degradation of organic pollutants in wastewater treatment.     

Mesoporous BiVO4/2D-g-C3N4 heterostructures for superior visible light-driven photocatalytic reduction of Hg(II) ions

In this contribution, a Z-scheme mesoporous BiVO₄/g-C₃N₄ nanocomposite heterojunction with a considerable surface area and high crystallinity was synthesized by a simple soft and hard template-assisted approach. This material demonstrates superior visible light-driven photocatalysis for the photoreduction of Hg(II) ions. TEM and XRD results show that the mesoporous BiVO₄ NPs, with a monoclinic phase and an ellipsoid-like shape, are highly dispersed onto the porous 2D surfaces of g-C₃N₄ nanosheets with a particle size of 5–10 nm. The obtained BiVO₄/g-C₃N₄ nanocomposites with a p-n heterojunction show significantly enhanced Hg(II) photoreduction efficiency compared to the mesoporous BiVO₄ NPs and pristine g-C₃N₄. Among all synthesized photocatalysts, the 1.2% BiVO₄/g-C₃N₄ nanocomposite indicated the highest photoreduction of Hg(II) performance, reaching ~ 100% within 60 min; this result is 3.9 and 4.5 –fold larger than that of the BiVO₄ NPs and pristine g-C₃N₄. The Hg(II) photoreduction rates highly increase to 208.90, 314.95, 411.23 and 418.68 μmol g⁻¹min⁻¹ for the mesoporous 0.4, 0.8, 1.2 and 1.6% BiVO₄/g-C₃N₄ nanocomposites, respectively. The reduction rate of the mesoporous 1.2% BiVO₄/g-C₃N₄ nanocomposite demonstrated a 5.2 and 3.8 times larger increase than that of the pristine g-C₃N₄ nanosheets and pure BiVO₄ NPs. The superior Hg(II) photoreduction efficiency was ascribed to decreased carrier recombination and the improved utilization of visible light by constructing BiVO₄/g-C₃N₄ nanocomposites with a p-n junction. Transient photocurrent measurement and photoluminescence spectra were employed to confirm the possible Hg(II) photoreduction mechanism over these BiVO₄/g-C₃N₄ photocatalysts. This research provides an accessible route for the nanoengineered design of mesoporous BiVO₄/g-C₃N₄ heterostructures that demonstrated unique photocatalytic performance.     

Synthesis of MoS2/g-C3N4 as a solar light-responsive photocatalyst for organic degradation

A novel molybdenum disulfide (MoS₂) and graphitic carbon nitride (g-C₃N₄) composite photocatalyst was synthesized using a low temperature hydrothermal method. MoS₂ nanoparticles formed on g-C₃N₄ nanosheets greatly enhanced the photocatalytic activity of g-C₃N₄. The photocatalyst was tested for the degradation of methyl orange (MO) under simulated solar light. Composite 3.0 wt.% MoS₂/g-C₃N₄ showed the highest photocatalytic activity for MO decomposition. MoS₂ nanoparticles can increase the interfacial charge transfer and thus prevent the recombination of photo-generated electron–hole pairs. The novel MoS₂/g-C₃N₄ composite is therefore shown as a promising catalyst for photocatalytic degradation of organic pollutants using solar energy.     

Construction of highly efficient 0D/2D Bi2MoO6/g-C3N4 heterojunctions for visible-light-driven photodegradation of 1-naphthol

Photocatalytic degradation is an ecologically benign method of reducing organic contaminants in wastewater. To remove the pollutant 1-naphthol, highly efficient 0D/2D Bi₂MoO₆/g-C₃N₄ heterojunctions were successfully assembled by a one-step hydrothermal method, where zero-dimension (0D) Bi₂MoO₆ nanoparticles were firmly bonded to two-dimension (2D) g-C₃N₄ nanosheets. 0D/2D Bi₂MoO₆/g-C₃N₄ exhibited exceptional degradation efficiency for 1-naphthol with a removal rate of 81.5% after 60 min of visible light irradiation. The enhanced photocatalytic ability was attributed to the matched band structures and tightly connected heterojunctions, which effectively prevented the recombination of photogenerated carriers. Besides, the photodegradation mechanism was revealed by investigating the catalysts' crystal phase, morphology, physicochemical and optical properties. This work introduces a novel method for one-step preparation of 0D/2D photocatalysts and advances the utilization of photodegradation for organic pollutants.     

Preparation of heterostructure g-C3N4/ZnO nanorods for high photocatalytic activity on different pollutants (MB,RhB, Cr(VI) and eosin)

The g-C₃N₄/ZnO nanorods were prepared by simple hydrothermal, grinding and calcination methods. The characterization of g-C₃N₄/ZnO nanorods was done by different analytical techniques such as SEM, TEM, XRD, XPS, FT-IR and UV–Vis. g-C₃N₄/ZnO nanorods with heterostructures have been successfully synthesized without changing the structure between the monomers, which broadens the visible light response range and improves several major pollutants in water degradation rate. Photocatalytic studies were done for the degradation of MB, RhB, Cr(VI) and eosin which are almost fully degraded. The experimental results show that the photocatalytic performance of the nanorods is much better than others. The g-C₃N₄/ZnO photocatalyst has excellent stability and repeated cycle performance. Basing on the results of comprehensive free radical trapping test and ESR tests, it is proposed that the main active substance of the catalyst for degrading dyes is ·0₂^-, and ·OH played significant roles in the degradation process. A good photocatalytic mechanism has been proven.     

Direct microwave synthesis of graphitic C3N4 with improved visible-light photocatalytic activity

The graphitic carbon nitride (g-C₃N₄) was rapidly synthesized via direct high-energy microwave heating approach. During the preparation process, only low-cost melamine and artificial graphite powders were used, without any metal catalysts or inert protective gas. The microstructure was investigated by using X-ray diffraction (XRD), Flourier transformed infrared (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). The spectra of XRD and HRTEM indicated that the obtained g-C₃N₄ had a high crystallinity. The optical spectra covering Photoluminescence (PL) and Ultraviolet-visible (UV–vis) were also measured at room temperature. PL peak and UV–vis absorption edge of the g-C₃N₄ were shown at 455 nm and 469 nm, respectively, indicating visible-light photocatalytic property. Finally, the photocatalytic activity of g-C₃N₄ was investigated and evaluated as photocatalyst for the photo-degradation of Rhodamine B (RhB) and Methyl Orange (MO) in aqueous solution under visible-light (λ>420 nm) irradiation, respectively. Results indicated that the g-C₃N₄ sample displayed an excellent performance of removing of RhB and MO due to the improved crystallinity and large surface area of 126 m²/g. After the visible-light photocatalytic reaction for 40 min, the decolorization ratios of RhB and MO reached up to 100% and 94.2%, respectively.     

Rational design of MoS2/g-C3N4/ZnIn2S4 hierarchical heterostructures with efficient charge transfer for significantly enhanced photocatalytic H2 production

The rational design of hierarchical heterojunction photocatalysts with efficient spatial charge separation remains an intense challenge in hydrogen generation from photocatalytic water splitting. Herein, a noble-metal-free MoS₂/g-C₃N₄/ZnIn₂S₄ ternary heterostructure with a hierarchical flower-like architecture was developed by in situ growth of 3D flower-like ZnIn₂S₄ nanospheres on 2D MoS₂ and 2D g-C₃N₄ nanosheets. Benefiting from the favorable 2D-2D-3D hierarchical heterojunction structure, the resultant MoS₂/g-C₃N₄/ZnIn₂S₄ nanocomposite loaded with 3 wt% g-C₃N₄ and 1.5 wt% MoS₂ displayed the optimal hydrogen evolution activity (6291 μmol g^?1 h^?1), which was a 6.96-fold and 2.54-fold enhancement compared to bare ZnIn₂S₄ and binary g-C₃N₄/ZnIn₂S₄, respectively. Structural characterizations reveal that the significantly boosted photoactivity is closely associated with the multichannel charge transfer among ZnIn₂S₄, MoS₂, and g-C₃N₄ components with suitable band-edge alignments in the composites, where the photogenerated electrons migrate from g-C₃N₄ to ZnIn₂S₄ and MoS₂ through the intimate heterojunction interfaces, thus enabling efficient electron-hole separation and high photoactivity for hydrogen evolution. In addition, the introduction of MoS₂ nanosheets highly benefits the improved light-harvesting capacity and the reduced H₂-evolution overpotential, further promoting the photocatalytic H₂-evolution performance. Moreover, the MoS₂/g-C₃N₄/ZnIn₂S₄ ternary heterostructure possesses prominent stability during the photoreaction process owing to the migration of photoinduced holes from ZnIn₂S₄ to g-C₃N₄, which is deemed to be central to practical applications in solar hydrogen production.     

Preparation and photocatalytic activity of g-C3N4/TiO2 heterojunctions under solar light illumination

The solar light sensitive g-C₃N₄/TiO₂ heterojunction photocatalysts containing 20, 50, 80, and 90 wt% graphitic carbon nitride (g-C₃N₄) were prepared by growing Titania (TiO₂) nanoparticles on the surfaces of g-C₃N₄ particles via one step hydrothermal process. The hydrothermal reactions were allowed to take place at 110 °C at autogenous pressure for 1 h. Raman spectroscopy analyses confirmed that an interface developed between the surfaces of TiO₂ and g-C₃N₄ nanoparticles. The photocatalyst containing 80 wt% g-C₃N₄ was subsequently heat treated 1 h at temperatures between 350 and 500 °C to improve the photocatalytic efficiency. Structural and optical properties of the prepared g-C₃N₄/TiO₂ heterojunction nanocomposites were compared with those of the pristine TiO₂ and pristine g-C₃N₄ powders. Photocatalytic activity of all the nanocomposites and the pristine TiO₂ and g-C₃N₄ powders were assessed by the Methylene Blue (MB) degradation test under solar light illumination. g-C₃N₄/TiO₂ heterojunction photocatalysts exhibited better photocatalytic activity for the degradation of MB than both pristine TiO₂ and g-C₃N₄. The photocatalytic efficiency of the g-C₃N₄/TiO₂ heterojunction photocatalyst heat treated at 400 °C for 1 h is 1.45 times better than that of the pristine TiO₂ powder, 2.20 times better than that of the pristine g-C₃N₄ powder, and 1.24 times better than that of the commercially available TiO₂ powder (Degussa P25). The improvement in photocatalytic efficiency was related to i) the generation of reactive oxidation species induced by photogenerated electrons, ii) the reduced recombination rate for electron-hole pairs, and iii) large specific surface area.     

Synthesis and photocatalytic activity of g-C3N4/ZnO composite microspheres under visible light exposure

In this paper, a novel g-C₃N₄/ZnO composite microspheres (CZCM) with enhanced photocatalytic activity under visible light exposure were successfully prepared by a self-assembly method followed by calcination in the air. A hierarchical structure in which ZnO microspheres were closely covered with g-C₃N₄ nanosheets was constructed. The microstructure and photocatalytic activities of the CZCM were characterized. The photocatalytic property of CZCM was evaluated by degrading solution Methyl Orange (MO) and Tetracycline (TC). The effects of varied contents of g-C₃N₄ on the photocatalytic capability of CZCM were systematically investigated and the results show that the optimized CZ-15% sample exhibit much higher photocatalytic degradation efficiency than that of bare g-C₃N₄ or ZnO under identical conditions. The analysis of Photoluminescence (PL) and photocurrent (PC) independently conformed that the photo-induced electron-hole (e^?-h⁺) pairs in the CZCM were effectively generated and responsible for the observed photocatalysis. The enhanced adsorption of visible-light and the effective charge separation on the surface of CZCM enabled significant improvement of photocatalytic performance. According to the experimental results and relative energy band levels of the two semiconductors, a possible photocatalysis mechanism for the reaction process is proposed.     

Amino group-rich porous g-C3N4 nanosheet photocatalyst: Facile oxalic acid-induced synthesis and improved H2-evolution activity

The reasonable modulation of tri-s-triazine structure units of g-C₃N₄ is an effective method to optimize its intrinsic electronic and optical properties, thus boosting its photocatalytic hydrogen-evolution activity. Herein, amino groups are successfully introduced into the tri-s-triazine structure units of g-C₃N₄ nanosheets to improve their H₂-evolution activity via a facile oxalic acid-induced supramolecular assembly strategy. In this case, the resulting amino group-rich porous g-C₃N₄ nanosheets display a loose and fluffy structure with a large specific surface area (70.41 m² g^?1) and pore volume (0.50 cm³? g^??1), and enhanced visible-light absorption (450–800 nm). Photocatalytic tests reveal that the amino group-rich porous g-C₃N₄ nanosheets (AP-CN1.0 nanosheets) exhibit a significantly elevated photocatalytic H₂-production activity (130.7 μmol h^?1, AQE = 5.58%), which is much greater than that of bulk g-C₃N₄ by a factor of 4.9 times. The enhanced hydrogen-generation performance of amino group-rich porous g-C₃N₄ nanosheets can be mainly attributed to the introduction of more amino groups, which can reinforce the visible-light absorption and work as the interfacial hydrogen-generation active centers to boost the photocatalytic hydrogen production. The present facile and effective regulation of tri-s-triazine structure units may provide an ideal route for the exploitation of novel and highly efficient g-C₃N₄ photocatalysts.     

One-pot-solid preparation of novel three-dimensional FexS1-x/g-C3N4 heterostructures for efficient photocatalytic mixed-pollutants removal

In order to overcome the problem of low photocatalytic rate of g-C₃N₄, the 3D Fe_xS_1-x/g-C₃N₄ heterojunction was prepared via a simple one-pot solid method. The X-Ray Diffraction (XRD) and scanning electron microscope (SEM) results demonstrated that the Fe_xS_1-x/g-C₃N₄ heterojunction was established and a g-C₃N₄ nanosheet was tightly bound to Fe_xS_1-x. Compared with g-C₃N₄ samples, Fe_xS_1-x coupling resulted in substantial enhancement of visible light absorption, moreover, the bandwidth of heterojunction was also expanded. In addition to effectively degrading RhB and reducing Cr(VI), the redox performance of Fe_xS_1-x/g-C₃N₄ was also increased in the Cr(VI)/RhB mixed system. Based on a variety of experimental results, the enhanced synergistic photocatalytic activity of the 3D Fe_xS_1-x/g-C₃N₄ heterojunction was attributed to enhancement of the separation of e^- and h⁺ in FeS_2, which resulted from the effective conversion of FeS into FeS₂ under UV-light irradiation. The type II heterojunction structure that was produced via one-pot solid fabrication also inhibited the recombination of electron/hole pairs. Fe_xS_1-x doping and heterojunction building improve the photocatalysis capacity of g-C₃N₄ and broaden the visible-light response of pure g-C₃N₄.     

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

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

Synthesis of dynamic g-C3N4/Fe@ZnO nanocomposites for environmental remediation applications

An effective g-C₃N₄/Fe@ZnO heterostructured photocatalyst was synthesized by a simple chemical co-precipitation method and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and ultraviolet–visible spectroscopy. Transmission electron microscopy revealed that 7-8 nm-sized 1%Fe@ZnO nanoparticles were evenly distributed on g-C₃N₄ nanosheets to form a hybrid composite. The photocatalytic effectiveness of the composites was assessed against methylene blue dye, and it was found that the 50%g-C₃N₄/Fe@ZnO photocatalyst was more efficient in harvesting solar energy to degrade dye than the ZnO, 1%Fe@ZnO, g-C₃N₄, g-C₃N₄/ZnO and (10, 25, 40, 60 & 75 wt%) g-C₃N₄/Fe@ZnO samples. The antibacterial competency of the samples was also explored against Gram-positive (Bacillus subtilis, Staphylococcus aureus and Streptococcus salivarius) and Gram-negative (Escherichia coli) bacteria through the well diffusion method. The 50%g-C₃N₄/Fe@ZnO nanocomposite exhibited a superior antibacterial action compared to that of the rest of the samples. The exceptionally improved photocatalytic and antimicrobial efficiency of the 50%g-C₃N₄/Fe@ZnO composite was primarily accredited to the synergic outcome of the interface established between Fe@ZnO nanoparticles and g-C₃N₄ nanosheets.