Graphitic Carbon Nitride Research Articles

Electrocatalytic efficiency of carbon nitride supported gold nanoparticle based sensor for iodide and cysteine detection

Extensive investigations are being conducted on gold nanoparticles focusing on their applications in biosensors, laser phototherapy, targeted drug delivery and bioimaging utilizing advanced detection techniques. In this work, an electrochemical sensor was developed based on graphite carbon nitride supported gold nanoparticles. Carbon nitride supported gold nanoparticles (Au–CN) was synthesized by applying a deposition-precipitation route followed by a chemical reduction technique. The composite system was characterized by X-ray diffraction and X-ray photo electron spectroscopy methods. Electron microscopy analysis confirmed the formation of gold nanoparticles within the size range of 5–15 nm on the carbon nitride support. Carbon nitride supported gold based sensor was employed for the electrochemical detection of iodide ion and l-cysteine. The limit of detection and sensitivity of the sensor was attained 8.9 μM and 0.96 μAμM⁻1cm⁻2, respectively, for iodide ion, while 0.48 μM and 5.8 μAμM⁻1cm⁻2, respectively, was achieved for the recognition of cysteine. Furthermore, a paper-based electrochemical device was developed using the Au–CN hybrid system that exhibited promising results in detecting iodide ions, highlighting its potential for economic and portable device applications.

Double-Fluorescent Response Spiropyran-Functionalized Graphitic Carbon Nitride Solvent Decoder and Nanofiber Mat-Based Visual Colorimetric Sensor for Humidity Detection within Grain Heaps.

Spiropyran-functionalized graphitic carbon nitride (MCH@g-C3N4) in acidic conditions was prepared for the first time. MCH@g-C3N4 exhibited dual-wavelength fluorescence emission with two distant bands and distinct solvatochromic behavior owing to the different molecular structures of spiropyran. A three-dimensional organic solvent decoder was fabricated for solvent identification based on the emission wavelength and fluorescence quantum yield of MCH@g-C3N4 in different polar solvents. The ratiometric fluorescence sensing of the water content in organic solvent was realized using water to induce the structural change of spiropyran. A solid-phase MCH@g-C3N4/polyvinylpyrrolidone (PVP) nanofiber mat-based sensor was prepared via cospinning MCH@g-C3N4 with hydrophilic PVP. A fluorescent humidity sensor was fabricated using a commercial syringe equipped with a stainless-steel needle (catcher) to obtain the air inside the grain heap, which enabled the accurate location of the sampling spot. The space between the syringe and piston was used as an enclosed sensing space. Thus, a simple, accurate, and intuitive visual colorimetric method for the internal humidity of a grain heap was realized by analyzing the recorded images.

Construction of Cu2Y2O5/g-C3N4 Novel Composite for the Sensitive and Selective Trace-Level Electrochemical Detection of Sulfamethazine in Food and Water Samples.

The most frequently used sulfonamide is sulfamethazine (SMZ) because it is often found in foods made from livestock, which is hazardous for individuals. Here, we have developed an easy, quick, selective, and sensitive analytical technique to efficiently detect SMZ. Recently, transition metal oxides have attracted many researchers for their excellent performance as a promising sensor for SMZ analysis because of their superior redox activity, electrocatalytic activity, electroactive sites, and electron transfer properties. Further, Cu-based oxides have a resilient electrical conductivity; however, to boost it to an extreme extent, a composite including two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets needs to be constructed and ready as a composite (denoted as g-C3N4/Cu2Y2O5). Moreover, several techniques, including X-ray diffraction analysis, scanning electron microscopy analysis, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy were employed to analyze the composites. The electrochemical measurements have revealed that the constructed g-C3N4/Cu2Y2O5 composites exhibit great electrochemical activity. Nevertheless, the sensor achieved outstanding repeatability and reproducibility alongside a low limit of detection (LOD) of 0.23 µM, a long linear range of 2 to 276 µM, and an electrode sensitivity of 8.86 µA µM-1 cm-2. Finally, the proposed GCE/g-C3N4/Cu2Y2O5 electrode proved highly effective for detection of SMZ in food samples, with acceptable recoveries. The GCE/g-C3N4/Cu2Y2O5 electrode has been successfully applied to SMZ detection in food and water samples.

Uniform nanorhombic α-Fe2O3 on g-C3N4 nanosheet: 2D/2D lattice matched S-scheme heterojunction towards efficient styrene oxidation and H2 evolution

The design and modification of heterojunction photocatalysts to enhance efficient interfacial charge transfer and superior photocatalytic performance are fundamental objectives in the field of solar-light-driven energy conversion and production. This study presents a novel S-scheme heterojunction which features lattice-matched morphological hetero-nanostructures, composing of two-dimensional (2D) graphitic carbon nitride (CN) loaded with uniformly distributed and size-consistent 2D nano-rhombohedral α-Fe2O3 (Fe2O3 NR/CN). The directional charge transfer in the lattice-matched S-scheme heterojunction was confirmed using a combination of in situ irradiated X-ray photoelectron spectroscopy, metal deposition experiments, electron paramagnetic resonance, and density functional theory calculations. The optimized heterojunction demonstrates exceptional photocatalytic activity, achieving a hydrogen generation rate that surpasses those of g-C3N4 and α-Fe2O3 alone by factors of 2.1 and 7, respectively. Additionally, this heterojunction exhibits an excellent styrene conversion rate of 94.1 % and a styrene epoxidation selectivity of 95.3 % under light irradiation at 80 °C using tert-butyl hydroperoxide (TBHP) as the oxidant. The incorporation of uniformly distributed nano-rhombohedral α-Fe2O3 particles with g-C3N4 successfully constructs an unobstructed interfacial pathway to form the lattice-matched S-scheme heterojunction, enabling efficient separation of photogenerated carriers. This unique structure provides a valuable reference for dual-functional photocatalytic reactions.

Scalable fabrication of high surface area g-C3N4 nanotubes for efficient photocatalytic hydrogen production

In this research, we present a novel facile, scalable, and template-free technique of synthesizing graphitic carbon nitride (g-C3N4) nanotubes for generating hydrogen through photocatalysis. The hybrid technique involves a two-fold mixing of the precursor materials melamine (M) and cyanuric acid (CA), involving ball milling followed by solution mixing. By varying the M:CA molar ratios, different compositions of g-C3N4 nanotubes were fabricated. The study focused on examining the surface characteristics and the photocatalytic hydrogen evolution performance of these nanotubes. Nanotubes with high specific surface area of 206 m2 g−1 for M:CA molar ratio of 1:3 and 178 m2 g−1 for M:CA molar ratio of 1:5 were produced, with H2 evolution rates of 543 μmol h−1 g−1 and 740 μmol h−1 g−1 respectively, which were an increase of 4 and 5-fold, respectively, in comparison to the pristine sample. The enhanced efficiency of hydrogen production through photocatalysis by nanotubes, when contrasted with pristine material, can be ascribed to their high crystallinity, superior specific surface areas, decreased recombination rates of electron-hole pairs generated during light exposure, and improved dynamics of charge carriers. This hybrid technique provides a new pathway for cost-effective fabrication of g-C3N4 nanotubes with substantial surface areas and high yield photocatalysts on an industrial scale, without the use of templates and hydrothermal processes for efficient hydrogen generation.

Strategy of constructing D-A structure and accurate active sites over graphitic carbon nitride nanowires for high efficient photocatalytic nitrogen fixation

Constructing photocatalysts for the stable and efficient production of NH3 is of excellent research significance and challenging. In this paper, the electron acceptor 5-amino-1,10-phenanthroline (AP) is introduced into the electron-donor graphitic carbon nitride (CN) framework by a simple heated copolymerization method to construct a donor–acceptor (D-A) structure. Subsequently, the phenanthroline unit is coordinated with transition metal Fe3+ ions to obtain the photocatalyst Fe(III)-0.5-AP-CN with better nitrogen fixation performance, and the average NH3 yield can reach 825.3 μmol g−1 h−1. Comprehensive experimental results and theoretical calculations show that the presence of the D-A structure can induce intramolecular charge transfer, effectively separating photogenerated electrons and holes. The Fe active sites can improve the chemisorption energy for N2, enhance the N-Fe bonding, and better activate the N2 molecule. Therefore, the synergistic effect between the construction of the D-A structure and the stably dispersed Fe active sites can enable CN to achieve high-performance N2 reduction to produce NH3.

Hydrothermal synthesis of BCQD@g-C3N4 nanocomposites supporting environmental sustainability: Organic dye removal and bacterial inactivation

Various studies are being carried out on the removal of organic dyes and the production of antibacterial agents. In this study, boron-doped carbon quantum dot (BCQD) was synthesized by hydrothermal method, and BCQD@g-C3N4 nanocomposite structure was synthesized using graphitic carbon nitride (g-C3N4) as the support material. The photocatalytic activity of the synthesized nanocomposite against MO, RhB dyes, and Escherichia coli (E. coli) bacteria was investigated. The surface, morphology, molecular, and crystal properties of BCQD@g-C3N4 were investigated using characterization methods such as Transmission electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Fluorescence (FL) spectrophotometer, and X-ray diffraction (XRD). As a result of TEM analysis, it was determined that the average particle size of BCQD was 5.1 ± 1.14 nm and showed a homogeneous distribution on 2D g-C3N4. In the XRD spectrum for BCQDs, the diffraction peak corresponding to the (002) amorphous carbon phase was observed at 21.65° In the PL spectrum of B-CQD@g-C3N4s, the emission value was observed at 458 nm. In the study conducted by taking advantage of the photocatalytic feature of BCQD@g-C3N4 nanocomposite, Rhodamine B (RhB) and Methyl orange (MO) were degraded by 65.58 % and 73.56 %, respectively, at the end of 120 min. Additionally, BCQD@g-C3N4 photocatalyst completely inhibited the growth of E. coli bacteria, which are frequently encountered in wastewater, at 90 minutes under sunlight. Escherichia coli (E. coli), which is frequently encountered in wastewater, BCQD@g-C3N4 completely prevented bacterial growth in the 90th minute under sunlight.

The coexistence of highly dispersed Pt2+ and Pt0 co-catalysts on chemically oxidized g–C3N4 via metal-support interaction: The effect of reduction time on Pt species and hydrogen evolution of Pt/g-C3N4 photocatalysts

Platinum (Pt) cocatalyst greatly enhances the photoactivity of the graphitic carbon nitride (g-C3N4) photocatalyst for photocatalytic H2 evolution where the Pt properties are critical to determine the photocatalytic activity. In this study, highly dispersed Pt was successfully loaded onto chemically oxidized g–C3N4 (OCN) via a hydrogen reduction process over different reduction time. OCN photocatalysts containing highly dispersed Pt2+/Pt0 exhibited outstanding charge separation efficiency and photocatalytic performance. Symmetrical –CO groups on the OCN surface specifically interacted with atomic Pt2+, and the Pt2+ atoms were stably reduced to Pt0 atoms along with the generation of –OH groups over time. The coexistence of Pt0 and Pt2+ promoted superior photocatalytic performance because the photoinduced charge transfer was facilitated by the Pt0 atoms, which was evidenced by the DFT calculation and the EIS, PL, and photocurrent response results. Consequently, after the 24 h reduction, the highly stable and active Pt2+/Pt0 atoms were effectively distributed over OCN, resulting in the highest HER activity at 4091.3 µmol g−1 h−1.

In Situ Synthesis and Characterization of Graphitic Carbon Nitride/Metakaolin Composite Photocatalysts Using a Commercial Kaolin

Kaolin-based graphitic carbon nitride (g-CNx) composite photocatalysts were synthesized from a urea precursor using a commercial kaolin. Structural characterization by X-ray diffraction and infrared spectroscopy (FTIR) verified the successful thermal polycondensation of g-CNx along the thermal dehydroxylation of kaolinite to metakaolin at 550 °C. The g-CNx content of the composites were estimated by thermogravimetry and CHN analysis, ranging from ca. 87 m/m% to ca. 2 m/m% of dry mass. The addition of kaolin during the composite synthesis was found to have a significant effect: the yield of in situ formed g-CNx drastically decreased (from ca. 4.9 m/m% to 3.8–0.1 m/m%) with increasing kaolin content. CHN and FTIR indicated the presence of nitrogen-rich g-CNx, having a specific surface area of 50 m2/g, which synergistically increased after composite synthesis to 67–82 m2/g. Estimated optical band gaps indicated the affinity to absorb in the visible light spectrum (λ < 413 nm). Photocatalytic activity upon both UV and artificial sunlight irradiation was observed by hydroxyl radical evolution, however, without the synergistic effect expected from the favorable porosity.

Merging semi-crystallization and multispecies iodine intercalation at photo-redox interfaces for dual high-value synthesis

The artificial photocatalytic synthesis based on graphitic carbon nitride (g-C3N4) for H2O2 production is evolving rapidly. However, the simultaneous production of high-value products at electron and hole sites remains a great challenge. Here, we use transformable potassium iodide to obtain semi-crystalline g-C3N4 integrated with the I-/I3- redox shuttle mediators for efficient generation of H2O2 and benzaldehyde. The system demonstrates a prominent catalytic efficiency, with a benzaldehyde yield of 0.78 mol g−1 h−1 and an H2O2 yield of 62.52 mmol g−1 h−1. Such a constructed system can achieve an impressive 96.25% catalytic selectivity for 2e- oxygen reduction, surpassing previously reported systems. The mechanism study reveals that the strong crystal electric field from iodized salt enhances photo-generated charge carrier separation. The I-/I3- redox mediators significantly boost charge migration and continuous electron and proton supply for dual-channel catalytic synthesis. This groundbreaking work in photocatalytic co-production opens neoteric avenues for high-value synthesis.

Enhancing self-induced polarization of PVDF-based triboelectric film by P-doped g-C3N4 for ultrasensitive triboelectric pressure sensors

Progress in wearable energy devices has reached the point of popularity over a few decades, as reflected by the rise of numerous sensors and storage devices driven by the urgent need for Internet of Things (IoT) applications. Triboelectric sensor (TES), on the basis of triboelectric nanogenerators (TENGs), exhibits high sensitivity and stability for pressure detection. Maximizing the sensitivity of the TES hinges upon the triboelectric layer selection capable of harnessing triboelectrification and electrostatic induction. Among them, PVDF has gained attention owing to its exceptional flexibility and tribo-negativity. However, the multiphase of pristine PVDF poses challenges, limiting its potential for TES with higher sensitivity. Tackling this issue, herein, we introduced phosphorus-doped graphitic carbon nitride (PCN) into the PVDF films to achieve self-induced polarization to enhance the sensitivity of the triboelectric pressure sensor. Through a controlled annealing temperature, phosphorus atoms are incorporated into the g-C3N4 (CN) matrix, enhancing the electronegativity of PVDF/PCN composite film while inducing a polarized β crystal phase in PVDF, thereby enabling greater attraction of positive charges. Consequently, the triboelectric output with PVDF/PCN composite film exhibited a significant improvement compared to the pristine PVDF film, achieving over a 100 V increment and the ability to power more than 100 LEDs. Furthermore, for the pressure-sensing applications, the TES with flexible PVDF/PCN triboelectric film exhibits a pressure sensitivity of 1.48 V/kPa, which shows a threefold increase in sensitivity compared to the pristine PVDF film (0.51 V/kPa), suggesting their great potential in self-powered wearable pressure sensors.

Sol-gel synthesis of Tb-doped lithium-nickel ferrite anchored onto g-C3N4 sheets for efficient photocatalytic degradation of organic dyes

Due to the advancement of industrialization, water pollution has become an alarming global issue. Many organic dyes, such as crystal violet and rhodamine B, present in industrial wastewater are causing severe health problems. Both of these dyes are carcinogenic. For their degradation, ferrites are synthesized in this research. Ferrites have high absorbing potential in visible regions and fast movement of charge carrier species. Therefore, the ferrites are potentially used in photocatalysis to purify contaminated water. Graphitic carbon nitride shows enhanced separation of charges, which lowers the rate of recombination of charge carrier species. Lithium nickel ferrite, lithium nickel ferrite doped with terbium, and its composite with graphitic carbon nitride (g-C3N4) are synthesized by sol-gel and ultra-sonication methods, respectively. The prepared samples are analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM), Electrochemical impedance spectroscopy (EIS), and Mott-Schottky analysis. The bandgap of LiNiFe2O4 and LiNiTbFe2O4 was 2.35 eV, and 1.87 eV, respectively. LiNiTbFe2O4@g-C3N4 degraded 86 % crystal violet and 83 % rhodamine B in 120 min. The LiNiTbFe2O4@g-C3N4 composite showed the maximum degradation and can be potentially used in wastewater treatment.

A Novel Acetylcholinesterase‐Based Electrochemical Biosensor Using g‐C3N4@MoS2 Nanohybrid for the Detection of Trichlorfon

ABSTRACTOrganophosphorus pesticides are commonly employed in agricultural fields due to their potent insecticidal properties and short environmental persistence. However, organophosphorus pesticides enter the human body through the food chain, surface, and groundwater, leading to irreversible damage to the nervous system. Therefore, monitoring the presence of organophosphorus pesticides in food is necessary to ensure human safety. Herein, an ultra‐sensitive electrochemical biosensor has been prepared by using graphitic carbon nitride decorated molybdenum sulfide (g‐C3N4@MoS2) as a catalyst for the detection of organophosphorus pesticides, trichlorfon. The synergistic effect of g‐C3N4@MoS2 boosts the electron transfer across the electrode surface, further contributing to the immobilization of acetylcholinesterase (AChE) enzyme using glutaraldehyde as a crosslinking agent. At optimum conditions, the developed biosensor (AChE/g‐C3N4@MoS2/ITO) demonstrated a broad linear range (5–100 nM) with a low detection limit (LOD) of 2.1 nM obtained using the equation 3σ/S where σ is the standard deviation and S is the sensitivity of the bioelectrode. In addition, the AChE/g‐C3N4@MoS2/ITO biosensor exhibited good stability and reproducibility, with satisfactory results for real sample analysis of trichlorfon detection.

Photodegradation of Polycyclic Aromatic Hydrocarbons Under Visible Light Using Modified g-C3N4 as Photocatalyst, Spectroscopic Studies

In this work, visible light was used for the photodegradation of polycyclic aromatic hydrocarbons (PAHs) using graphitic carbon nitride (g-C3N4) and it was modified as a photocatalyst. Modification of g-C3N4 was performed using SDS, MIL-101, and TiO2. The UV–Vis spectroscopy, XRD, and FTIR spectrometry were applied for characterization. The photodegradation of pyrene and anthracene was investigated using the photocatalyst. Results indicated that the modified photocatalytic has better photocatalytic properties than that unmodified due to the more surface area and better optical properties of the former. Results also revealed that the photodegradation efficiency significantly improved by using g-C3N4@TiO2 so that it degrades about 95% of the pyrene molecules within 12 h. While g-C3N4@ SDS and g-C3N4@ MIL-101 are degraded very low (below 10%) under the same circumstances. The LED lamp (8 W) was used as a source of radiation. Photodegradation of anthracene was also investigated; results revealed that the anthracene is degraded more quickly than the pyrene, so that after 6 h about 98% of anthracene is decomposed. The mechanism of photodegradation was discussed.

Antibacterial and Anticorrosive Hydrogel Coating Based on Complementary Functions of Sodium Alginate and g-C3N4.

Graphitic carbon nitride (g-C3N4, CN) has emerged as a promising photocatalytic material due to its inherent stability, antibacterial properties, and eco-friendliness. However, its tendency to aggregate and limited dispersion hinder its efficacy in practical antibacterial applications. To address these limitations, this study focuses on developing a composite hydrogel coating, in which sodium alginate (SA) molecules interact electrostatically and through hydrogen bonding to anchor CN, thereby significantly improving its dispersion. The optimal CN loading of 35% results in a hydrogel with a tensile strength of 120 MPa and an antibacterial rate of 99.87% within 6 h. The enhanced mechanical properties are attributed to hydrogen bonding between the -NH2 groups of CN and the -OH groups of SA, while the -OH groups of SA facilitate the attraction of photogenerated holes from CN, promoting carrier transfer and separation, thereby strengthening the antibacterial action. Moreover, the hydrogel coating exhibits excellent antibacterial and corrosion resistance capabilities against Pseudomonas aeruginosa on 316L stainless steel (316L SS), laying the foundation for advanced antimicrobial and anticorrosion hydrogel systems.

Graphitic carbon nitride nanosheet supported silica nanochannel film for enhanced electrochemiluminescence sensing of 2,4,6-trichlorophenol and prochloraz.

The development of simple, rapid, and sensitive methods for detecting pesticide in environmental and food samples holds significant importance. Electrochemiluminescence (ECL) sensing platforms with high resistance to interference and contamination, and reduced consumption of ECL emitters, are highly desirable for such applications. In this work, we present an ECL sensing platform based on a graphitic carbon nitride nanosheets (CNNS) supported vertically ordered mesoporous silica film (VMSF) modified glassy carbon electrode (GCE) for the highly sensitive detection of the environmental pollutant 2,4,6-trichlorophenol (TCP) and the broad-spectrum insecticide prochloraz. Two-dimensional (2D) CNNS were synthesized by exfoliating bulk graphitic carbon nitride (g-C3N4) using concentrated sulfuric acid, serving as a novel conductive and adhesive layer for the growth of a stable VMSF on GCE via an electrochemical assistance self-assembly (EASA) method to prepare VMSF/CNNS/GCE. The electrostatic enrichment capability of VMSF nanochannels for the positively charged ECL emitter tris(2,2'-bipyridyl)ruthenium(ii) (Ru(bpy)3 2+) realized stable and significantly enhanced ECL signals at a low concentration of Ru(bpy)3 2+ (10 μM). Based on the quenching effect of TCP on the ECL signal of Ru(bpy)3 2+, highly sensitive ECL detection of TCP was achieved by the VMSF/CNNS/GCE with a linear range from 10 nM to 0.7 mM and a low detection limit (DL) of 2.2 nM. As the metabolic end product of prochloraz is TCP, indirect ECL detection of prochloraz was also accomplished by measuring the produced TCP. Combined with anti-fouling and anti-interference abilities, as well as signal amplification of VMSF, the developed VMSF/CNNS/GCE sensor enabled the sensitive ECL detection of TCP in pond water and prochloraz in orange peel extract.

Synthesis of phthalocyanine/C3N4 structures and investigation of photocatalytic activities in the oxidation reaction of 4-nitrophenol

Photocatalytic oxidation is an advanced oxidation technique widely preferred for the removal of pollutants in wastewater. In this work, paramagnetic metallo-phthalocyanines EB2 and EB3 (Co(II)phthalocyanine and Cu(II)phthalocyanine) have been synthesized and characterized. They were interfaced with C3N4 (graphitic carbon nitride) to prepare metallophthalocyanines/C3N4 structures (EB2-C3N4 and EB3-C3N4) using ultrasonic methods. New structures were identified with FT-IR, SEM and TGA. The photocatalytic performances of EB2-C3N4 and EB3-C3N4 for reaction with p-nitrophenol (p-NP) were established. The product selectivity for industrially important benzaldehyde was 85.1% for EB2-C3N4 and 80.6% for EB3-C3N4. EB2-C3N4 showed good potential for p-NP photocatalyic oxidation with high turn-over number (TON) and turn-over frequency (TOF) (390 and 1565) over 15 min. Upon excitation of EB2-C3N4 and EB3-C3N4 with light, 4-nitrophenol was easily reduced to hydroquinone, prompted by electron transfer from C3N4 to phthalocyanine and from phthalocyanine to 4-nitrophenol. Computational investigations were used to determine the energies of the highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO) of EB2, EB3 and C3N4.

Enhanced Piezocatalytic Performance through Self-Assembly Synthesis of Carbon-Rich Graphitic Carbon Nitride

Enhanced Piezocatalytic Performance through Self-Assembly Synthesis of Carbon-Rich Graphitic Carbon Nitride

New insights into the mechanism for Fe coordination promoting photocatalytic reduction of Cr(VI) by graphitic carbon nitride: The boosted transformation of Cr(V) to Cr(III)

Fe coordination is effective to promote photocatalytic Cr(VI) reduction by graphitic carbon nitride (g-C3N4) from wastewater; however, the role of Fe coordination in the Cr intermediate transformation is still unknown. Herein, a Cr intermediate, Cr(V), is detected by electron paramagnetic resonance and its generation and consumption kinetics are constructed for studying the visible-light photocatalytic processes of g-C3N4 and Fe anchored g-C3N4. The inclusion of Fe increased the photocatalytic Cr(VI) removal from 26.8 % to 51.3–85.6 %. The results reveal that Fe coordination of trivalent state can greatly enhance photocatalytic Cr(VI) reduction performance mainly through promoting interfacial electron transfer from g-C3N4 to Cr(V). Compared with pure g-C3N4, increasing Fe(III)/Fe(II) ratio of coordinated Fe species results in 8–11 times of enhancement of photocatalytic Cr(VI) reduction performance, 1–2 times of enhancement of photocatalytic Cr(V) generation, and 8–9 times of enhancement of photocatalytic Cr(V) consumption. This suggests the rate-limiting step for Cr(VI) reduction by g-C3N4-based photocatalysts is the transformation process of Cr(V) to Cr(III) and also illustrates the important role of the coordinated Fe(III) species in the photocatalytic transformation of Cr intermediates. This study deepens the understanding of Fe-coordination-promoted photocatalytic Cr(VI) reduction process and sheds light on developing high-performance g-C3N4-based photocatalysts for Cr(VI) removal from wastewater.

Activation of peroxydisulfate by endogenous nitrogen-doped carbon for efficient degradation of sulfamethoxazole

An endogenous nitrogen-doped carbon (ENC) was synthesized to activate peroxydisulfate (PDS) for Sulfamethoxazole (SMX) removal using graphitic carbon nitride as the raw material. The characterization of the surface properties of ENC demonstrated that ENC is rich in functional groups and mesoporous structure, coupled with a very large specific surface area (1034.6 m²·g−1). The ENC/PDS system demonstrated up to 98.5% degradation capability of SMX within 30 min and maintained over 80% in a complex aqueous environment. Further investigation of the intrinsic mechanism of SMX decomposition by ENC/PDS confirmed the dominant roles of surface-bound radicals and mediated electron transfer, with surface-bound SO₄·⁻ and a transient active complex (PDS/ENC*) identified as the key reactive species. This study significantly broadens the scope of nitrogen-doped carbon materials in environmental treatment by conducting an extensive investigation of the ENC/PDS/SMX system.