Novel magnetically separable g-C3N4/AgBr/Fe3O4 nanocomposites as visible-light-driven photocatalysts with highly enhanced activities

In this study, we report novel magnetically separable g-C₃N₄/AgBr/Fe₃O₄ nanocomposites as visible-light-driven photocatalysts. The preparation method was simple, large-scale, and low-temperature and did not require any additives or post preparation treatments. The nanocomposites were characterized using X-ray diffraction, transmission electron microscopy, energy dispersive analysis of X-rays, UV–vis diffuse reflectance spectroscopy, Fourier transform-infrared spectroscopy, thermogravimetric analysis, and vibrating sample magnetometry techniques. Photocatalytic activity of the nanocomposites was investigated by degradation of rhodamine B under visible-light irradiation. The nanocomposite with 4:1 weight ratio of g-C₃N₄/AgBr to Fe₃O₄ exhibited superior activity in the degradation reaction. Activity of this nanocomposite was about 5.3 and 5-fold higher than those of g-C₃N₄, and g-C₃N₄/Fe₃O₄, respectively. Moreover, we investigated the influence of refluxing time, calcination temperature, and scavengers of reactive species on the degradation activity. Finally, the photocatalyst was magnetically separated, with high efficiency, from the treated solution after five successive cycles.     

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.     

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.     

Enhanced visible-light photocatalytic properties of g-C3N4 by coupling with ZnAl2O4

A series of g-C₃N₄/ZnAl₂O₄ composites were prepared using a conventional calcination method and the heterostructures were systematically characterized. It was found that the combination of g-C₃N₄ with ZnAl₂O₄ significantly improve their photocatalytic activities. The optimum photocatalyst of composite is at 5% (wt%) of ZnAl₂O₄, whose degradation efficiency for methyl orange (MO) was 96% within 120 min under visible-light irradiation. The formation of heterojunction between g-C₃N₄ and ZnAl₂O₄ can facilitate efficient charge separation of photogenerated electron-hole pairs, which were confirmed by electrochemical impedance spectroscopy (EIS). As a result, the photocatalytic properties of composites were enhanced.     

Novel visible light-induced g-C3N4–Sb2S3/Sb4O5Cl2 composite photocatalysts for efficient degradation of methyl orange

A series of g-C₃N₄–Sb₂S₃/Sb₄O₅Cl₂ (SCL-CX) composite photocatalysts were successfully prepared via a hydrothermal method. The as-prepared materials were characterized by TM3000, powder X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and UV–vis diffuse reflectance spectra (UV–vis DRS). The obtained photocatalyst showed higher photocatalytic activity than pure g-C₃N₄, Sb₄O₅Cl₂ and Sb₂S₃/Sb₄O₅Cl₂ (SCL). The optimum photocatalytic of the composite with the mass of 170 mg g-C₃N₄ and a degradation efficiency up to 95% for methyl orange (MO) under visible light was achieved within 60 min. The enhanced photocatalytic performance could be attributed to the stronger absorption in the visible region and the more efficient electron–hole separation.     

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.     

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.

     

Constructing 0D/2D Z-Scheme Heterojunction of CdS/g-C3N4 with Enhanced Photocatalytic Activity for H2 Evolution

0D/2D Pt-C₃N₄/CdS heterojunction photocatalyst were fabricated with CdS quantum dots interspersed on g-C₃N₄ nanosheets via successive ionic layer absorption process. The obtained Pt-C₃N₄/CdS Z-scheme heterojunction with Pt cocatalyst deposited on g-C₃N₄ nanosheets exhibited H₂ production rate of 35.3 mmol g^?1 h^?1, which is 3.1 times higher than that of Pt-CdS/C₃N₄. The enhanced photocatalytic activity are attributed to the Z-scheme charge carrier transfer mechanism with stronger redox ability. The photocatalytic mechanism of the CdS/g-C₃N₄ composite is investigated and demonstrated in this work. It may provide unique insights to design 0D/2D Z-scheme heterojunction photocatalyst systems using a facile method for highly efficient H₂ production.

Graphic Abstract

Schematic illustration of charge transfer modulated by the metal cocatalyst selective deposition on heterojunction-type II (a) and direct Z-Scheme mechanisms (b) over the C₃N₄/CdS heterostructure composites under visible light irradiation.

     

Hydrothermal synthesis and visible-light photocatalytic activity of porous peanut-like BiVO4 and BiVO4/Fe3O4 submicron structures

Porous peanut-like BiVO₄ and BiVO₄/Fe₃O₄ submicron structures were synthesized by a template-free hydrothermal process at 160 °C for 24 h. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM) and UV–vis spectroscopy. The photocatalytic activity of BiVO₄ and BiVO₄/Fe₃O₄ submicron structures were evaluated for the degradation of Rhodamine B (RhB) and methylene blue (MB) under visible light irradiation with and without the assistance of H₂O₂. According to the experimental results obtained, porous peanut-like BiVO₄/Fe₃O₄ composite photocatalyst shows higher photocatalytic activity in the H₂O₂-assisted system under visible light irradiation compared to BiVO₄. Recycling test on the BiVO₄/Fe₃O₄ composite photocatalyst for the degradation of RhB under visible light irradiation indicates that the composite photocatalyst is stable in the H₂O₂-assisted system in five cycles. Therefore, this composite photocatalyst will be beneficial for efficient degradation of organic pollutants present in water and air under solar light.     

Visible light-activated degradation of microcystin-LR by ultrathin g-C3N4 nanosheets-based heterojunction photocatalyst

Microcystins (MCs) is a harmful toxin generated by blue-green algae in water, which has seriously threatened the ecological safety of water and human body. It is urgent to develop new catalysts and techniques for the degradation of MCs. A feasible electrostatic self-assembly method was carried out to synthesize BiVO₄/g-C₃N₄ heterojunction photocatalyst with highly efficient photocatalytic ability, where BiVO₄ nanoplates with exposed {010} facets anchored to the g-C₃N₄ ultrathin nanosheets. The morphology and microstructure of the heterojunction photocatalysts were identified by XRD, SEM, TEM, XPS, and BET. The g-C₃N₄ nanosheets have huge surface area over 200 m²/g and abundant mesoporous ranging from 2-20 nm, which provides tremendous contact area for BiVO₄ nanoplates. Meanwhile, the introduction of BiVO₄ led to red-shift of the absorption spectrum of photocatalyst, which was characterized by UV-vis diffuse reflection spectroscopy (DRS). Compared with pure BiVO₄ and g-C₃N₄, the BiVO₄/g-C₃N₄ heterojunction shows a drastically enhanced photocatalytic activity in degradation of microcystin-LR (MC-LR) in water. The MC-LR could be removed within 15 minutes under the optimal ratio of BiVO₄/g-C₃N₄. The outstanding performance of the photocatalyst is attributed to synergetic effect of interface Z-scheme heterojunction and high active facets {010} of BiVO₄ nanoplates, which provides an efficient transfer pathway to separate photoinduced carriers meanwhile endows the photocatalysts with strong redox ability.     

A facile and novel construction of attapulgite/Cu2O/Cu/g-C3N4 with enhanced photocatalytic activity for antibiotic degradation

A high-performance photocatalyst, attapulgite/Cu₂O/Cu/g-C₃N₄ (ATP/Cu₂O/Cu/g-C₃N₄), was constructed via a one-pot redox strategy under anoxic calcination. The as-prepared composites were characterized by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂ adsorption-desorption isotherms (BET), photoluminescence emission (PL), and electrochemical impedance spectra (EIS). Results indicate that ultra-fine CuO nanoparticles on the surface of rod-like attapulgite are in-situ reduced by NH₃ gas to generate Cu and minority Cu₂O during the pyrocondensation of melamine. Meanwhile, the generated g-C₃N₄ membrane is uniformly encapsulated on the surface of attapulgite/Cu₂O/Cu to assemble Z-scheme Cu₂O/Cu/g-C₃N₄ heterostructure. ATP/Cu₂O/Cu/g-C₃N₄ shows improved visible light response ability and hole-electron suppression compared with ATP/g-C₃N₄. The photocatalytic performance and mechanism of the obtained photocatalyst for antibiotic degradation were evaluated by UV–Vis spectrometer and liquid chromatograph. ATP/Cu₂O/Cu/g-C₃N₄ can exhibit favorable photocatalytic activity and reusability for chloramphenicol. In addition, h⁺ and·OH radicals are the main active sites in the photocatalytic process, and Cu species play a vital role in separation and retarding recombination of electron-hole pairs.     

Intensifying the photocatalytic degradation of methylene blue by the formation of BiFeO3/Fe3O4 nanointerfaces

A novel highly efficient photocatalyst composite BiFeO₃/Fe₃O₄ has been synthesized by mechanosynthesis and applied to the degradation of Methylene Blue under visible light. Structural, optical and photocatalytic properties of the proposed photocatalyst composites are carefully investigated. The nanointerfaces, associated to ferrous Fe²⁺ ions of the Fe₃O₄ nanoparticles, improve the photocatalytic efficiency when compared with pure BiFeO₃ or Fe₃O₄. The time required to the complete degradation of Methylene Blue solution is 40 min for the sample with 20% of Fe₃O₄ which is more than 7 times faster than the time required using BiFeO₃ alone. Moreover, with the addition of H₂O₂ a complete degradation is achieved just after 10 min, which is faster than any other photocatalytic reaction reported for BiFeO₃-based materials. This enhancement is assumed to be related to an electron drain process due to the difference between energy levels of the conduction bands of BiFeO₃ and Fe₃O₄ combined with the direct Fenton-like process associated with the Fe²⁺ ions of the composites.     

Performance of magnetically recoverable core–shell Fe3O4@Ag3PO4/AgCl for photocatalytic removal of methylene blue under simulated solar light

A novel magnetically recoverable core–shell Fe₃O₄@Ag₃PO₄/AgCl photocatalyst exhibiting rapid magnetic separation, stability and high photocatalytic activity under simulated solar light has been developed. Briefly, Ag₃PO₄ is immobilized on Fe₃O₄ nanoparticles and then an AgCl shell is formed by in situ ion exchange. The complete degradation of the methylene blue (MB) over the Fe₃O₄@Ag₃PO₄/AgCl photocatalyst only took about 60 min, much faster than WO₃–Pd photocatalyst. Fe₃O₄@Ag₃PO₄/AgCl nanocomposites can be easily recovered by a magnet, and reused at least five times without any appreciable reduction in photocatalytic efficiency.     

Facial synthesis of a novel Ag4V2O7/g-C3N4 heterostructure with highly efficient photoactivity

A novel Ag₄V₂O₇/g-C₃N₄ heterostructure was synthesized by a facial etching method in ammonia solution using Ag₂VO₂PO₄/g-C₃N₄ as a self-sacrifice precursor. With the concentration of ammonia solution increasing from 0.05 to 0.2 M, phase transformation took place, described as: Ag₂VO₂PO₄/g-C₃N₄ → Ag₂VO₂PO₄/Ag₄V₂O₇/g-C₃N₄ → Ag₄V₂O₇/g-C₃N₄. Compared with pristine Ag₂VO₂PO₄/g-C₃N₄, the etched samples of Ag₄V₂O₇/g-C₃N₄ and Ag₂VO₂PO₄/Ag₄V₂O₇/g-C₃N₄ exhibited dramatically improved activity for the degradation of methylene blue (MB), methyl orange (MO) and imidacloprid under visible light irradiation. When etched with 0.15 M ammonia solution, an Ag₄V₂O₇/g-C₃N₄ heterostructure was obtained that exhibited the highest photoactivity. This photocatalyst was nearly 9.1, 3.0, and 24.3 times more efficient than pristine Ag₂VO₂PO₄/g-C₃N₄ for degradation of MB, MO and imidacloprid, respectively. The excellent photocatalytic performance can be ascribed to the as-obtained well-defined Ag₄V₂O₇/g-C₃N₄ heterojunction, which improves the separation and transfer efficiency and prolongs the lifetime of photoinduced charges. In addition, the stability and dominant radicals were investigated.     

Ti3C2@TiO2/g-C3N4 heterojunction photocatalyst with improved charge transfer for enhancing visible-light NO selective removal

Control of Nitrogen dioxide (NO₂) byproducts is of great importance for the photocatalytic NO removal and environmental remedy. However, individual semiconductor photocatalysts generally show limited capabilities for selective NO removal due to severe charge recombination and inadequate redox potentials. Herein, the cotton-like g-C₃N₄ was modified with Ti₃C₂@TiO₂ to construct a heterojunction photocatalyst Ti₃C₂@TiO₂/g-C₃N₄, which showed outperformed photocatalytic NO removal and MB degradation abilities compared to the individual photocatalysts under visible light irradiation. The UV–vis absorption spectra and photoluminescence (PL) spectra confirmed that Ti₃C₂@TiO₂/g-C₃N₄ photocatalyst was endowed with superior light utilization and separation/transfer ability of charge carriers due to the presence of n-n heterojunction and Schottky barrier. Furthermore, the g-C₃N₄, Ti₃C₂, and TiO₂ were closely contacted showing a high specific surface area, which promoted the charge transfer and the exposure of more active sites, further inducing the formation of more active species. Therefore, the designed photocatalyst delivered a high removal rate of NO and a suppressed discharge of NO₂. Notably, the photocatalyst Ti₃C₂@TiO₂/g-C₃N₄ also presented superior NO removal ability during the cycling experiment, indicating their outstanding stability and recyclability. Besides, the effects of active species were monitored using a trapping experiment to propose probable photocatalytic mechanism. This study could shed a new light to the design of photocatalyst for air purification in the future.     

Preparation of g-C3N4/MoS2 Composite Material and Its Visible Light Catalytic Performance

The g-C₃N₄ nanosheet was prepared by calcination method, the MoS₂ nanosheet was prepared by hydrothermal method. The g-C₃N₄/MoS₂ composites were prepared by ultrasonic composite in anhydrous ethanol. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible spectroscopy, and photoluminescence techniques were used to characterize the materials. The photocatalytic degradation of Rhodamine B (Rh B) by g-C₃N₄/MoS₂ composites with different mass ratios was investigated under visible light. The results show that a small amount of MoS₂ combined with g-C₃N₄ can significantly improve photocatalytic activity. The g-C₃N₄/MoS₂ composite with a mass ratio of 1:8 has the highest photocatalytic activity, and the degradation rate of Rh B increases from 50 to 99.6%. The main reason is that MoS₂ and g-C₃N₄ have a matching band structure. The separation rate of photogenerated electron–hole pairs is enhanced. So the g-C₃N₄/MoS₂ composite can improve the photocatalytic activity. Through the active material capture experiment, it is found that the main active material in the photocatalytic reaction process is holes, followed by superoxide radicals.

     

Porous-C<Subscript>3</Subscript>N<Subscript>4</Subscript> with High Ability for Selective Adsorption and Photodegradation of Dyes Under Visible-Light

Porous-C₃N₄ with high photocatalytic activity of anionic dyes was successfully synthesized by a SiO₂-template method. Its photocatalytic selectivity could easily be switched to cationic dye via a simple post-treatment in NaOH solution. Through careful investigation of influencing parameters (the photocatalytic performances, the structure and surface characteristics of the catalysts), the selective degradation of various dyes is closely related to the adsorption selectivity of the porous g-C₃N₄ catalysts, which originated from the different surface charge. This study provides a new insight into developing metal-free g-C₃N₄ photocatalyst with high efficiency and selectivity in environmental purification.     

Novel g-C3N4 nanosheets/CDs/BiOCl photocatalysts with exceptional activity under visible light

We fabricated novel ternary nanocomposites through integration of C-dots (carbon dots), BiOCl, and nanosheets of graphitic carbon nitride (g-C₃N₄ nanosheets) by a cost-effective route. The fabricated photocatalysts were subsequently characterized by XRD, EDX, TEM, HRTEM, XPS, FT-IR, UV-vis DRS, TGA, BET, and PL methods to gain their structure, purity, morphology, optical, textural, and thermal properties. In addition, the degradation intermediates were identified by gas chromatography-mass spectroscopy (GC-MS). Photocatalytic performance of the synthesized samples was studied by photodegradations of three cationic (RhB, MB, and fuchsine), one anionic (MO) dyes, one colorless (phenol) pollutant and removal of an inorganic pollutant (Cr(VI)) under visible light. It was revealed that the ternary nanocomposite with loading 20% of BiOCl illustrated superlative performances in the selected photocatalytic reactions compared with the corresponding bare and binary photocatalysts. Visible-light photocatalytic activity of the g-C₃N₄ nanosheets/CDs/BiOCl (20%) nanocomposite was 42.6, 27.8, 24.8, 20.2, and 15.9 times higher than the pure g-C₃N₄ for removal of RhB, MB, MO, fuchsine, and phenol, respectively. Likewise, the ternary photocatalyst showed enhanced activity of 15.3 times relative to the g-C₃N₄ in photoreduction of Cr(VI). Moreover, the ternary nanocomposite exhibited excellent chemical stability and recyclability after five cycles. Finally, the mechanism for improved photocatalytic performance was discussed based on the band potential positions.     

Ionic liquid-assisted preparation of g-C3N4/RGO co-intercalated CuBi2O4 hierarchical nanoflower and enhancement of the photocatalytic activity

A new p-n type CBO/CN/RGO ternary heterojunction photocatalyst combining three-dimensional multi-stage rosette CuBi₂O₄ and two-dimensional g-C₃N₄ and RGO flakes was successfully prepared by ionic liquid-assisted hydrothermal method. The successful construction of p-n heterojunctions of CBO/CN/RGO composites was verified by means of UV–vis diffuse reflection, Mott Schottky curves and TEM, and construction the heterojunctions significantly improved that of the transfer and transport speed of photogenerated carriers. The photocatalytic degradation of MO by CBO/CN/RGO-6% reached 91.83% within 150 min, while the kinetic constants of degradation k were 9.7 and 7.9 times greater than those of single-phase CBO and g-C₃N₄, respectively. Three cycles of experiments demonstrated that the degradation efficiency of CBO/CN/RGO-6% composites remained above 88% for RhB, which fully proved that the CBO/CN/RGO-6% composites possessed good chemical stability. Based on its excellent photocatalytic performance and good stability, CBO/CN/RGO-6% is expected to be the preferred material for environmental wastewater treatment.     

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.