Exfoliation Of Graphitic Carbon Nitride Research Articles

Comparative investigation of the characterization and photoactivity of gold-decorated graphitic carbon nitride: A study aspect of various synthesis approaches

In recent decades, photocatalysis has been broadly considered one of the potential approaches for different environmental and medicinal applications. Different synthesis methods possess different benefits and drawbacks, requiring thorough comparison to optimize the usage of precursors, equipment, and photocatalysis activity of the materials. In this study, the gold-decorated graphitic carbon nitride nanocomposites (AuCN) were successfully fabricated via different methods, including hydrothermal (HT), radiation under visible light (Ir), and chemical reduction (VC). The characterization of the prepared materials was investigated, which showed an efficient exfoliation of graphitic carbon nitride (g-C3N4 − CN) sheets and uniform embedment of gold nanoparticles (AuNPs). The AuCN sample synthesized from the chemical approach (AuCN-VC) showed the strongest signals of the AuNPs content, while the material prepared from the hydrothermal method (AuCN-HT) indicated a better CN crystalline structure. Furthermore, the photoactivity of the fabricated materials was also compared with pristine CN via the analysis of band structure, elucidating an improvement in the band gap energy to 2.25, 2.59, and 2.68 eV for the hydrothermal, irradiation, and chemical approaches, respectively. According to the photocatalysis results, AuCN-VC possessed the highest photo behavior under visible illumination with the hydrogen peroxide yield production at 271.5 mM/g.h. Meanwhile, the observation in the antibacterial activity exhibited the greatest performance regarding AuCN-HT with the recorded inhibition zone diameters of 9.3 and 8.6 mm against P. aeruginosa and S. aureus, respectively, under photo-excitation. According to the aforementioned results, the synthesized AuCN composites suggest great potential in a wide range of applications in environmental remediation and renewable production.

Exfoliated carbon nitrides for corrosion prevention in radiators: Temperature-dependent corrosion analysis

This article outlines the preparation and exfoliation of graphitic-carbon nitride (GCN) by thermal polymerization technique using urea proceeded by the hydrothermal approach for the application of corrosion resistance in radiators. The prepared sample was characterized by using various methods. X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) confirmed the purity of GCN, and Surface morphology results revealed the formation of spherical-shaped GCN. Herein, graphitic carbon nitride (GCN) was synthesized to enhance its corrosion-resistance performance on mild steel (MS) under a seawater atmosphere. The corrosion behaviour of the graphitic-carbon nitride (GCN) synthesized by the hydrothermal method was examined by conducting electrochemical corrosion tests in a 3.5% NaCl medium under three different temperatures. The excellent temperature dependant electro-catalytic activity of the prepared GCN was analysed. The hydrothermal exfoliation process highly enhances the structural, optical, and electrochemical properties like corrosion resistance and stability of the prepared GCN. This study demonstrates that hydrothermally exfoliated GCN exhibits low corrosion rates and high electrochemical corrosion resistance, which could be a potential candidate for corrosion inhibitors in radiators.

Steam exfoliation of graphitic carbon nitride as efficient route toward metal-free electrode materials for hydrogen production

This study demonstrates the potential of obtaining nanostructured materials based on g-C3N4 with a high specific surface area for use as efficient electrode materials for hydrogen production. The study uses a novel method of g-C3N4 exfoliation that increases the specific surface area of the starting material by a factor of three. Nanocrystalline g-C3N4 is obtained through the thermolysis of urea and treated with steam in a specified temperature range. The resulting series is analyzed using a range of physicochemical methods to determine the optimal temperature for steam exfoliation. Catalytic electrochemical tests are carried out in the electrolytic reforming of ethanol. It has been demonstrated that steam exfoliation can boost the rate of electrocatalytic reforming by 1.3 times while decreasing the amount of hydrogen evolution overpotential. The results of this study demonstrate the potential for the use of steam exfoliation as an effective method for obtaining high-performing electrode materials for hydrogen production.

Optimization of thermal exfoliation of graphitic carbon nitride for methylparaben photocatalytic degradation under simulated solar radiation

A full factorial 32 design was used to optimize the exfoliation treatment of g-C3N4 to enhance its photocatalytic performance for methyl paraben degradation.

Lysozyme-assisted ultrasonic exfoliation of graphitic carbon nitride into highly stable nanosheets with enhanced bactericidal capacity

Graphitic carbon nitride (g-C3N4) is a visible light-responsive photocatalytic material with important application prospects in many fields. However, the interaction between g-C3N4 monolayers makes it easy to aggregate and precipitate in aqueous solutions, and it is necessary to prepare stable g-C3N4 aqueous dispersions for their applications. Here we propose a facile, green, and low-cost method for the preparation of stable g-C3N4 dispersions by ultrasonicating g-C3N4 in lysozyme (LYZ) solution. The LYZ was adsorbed on the surface of g-C3N4 through non-covalent interactions such as electrostatic interaction, hydrogen bonding and π-cation interaction to prevent the aggregation of g-C3N4 nanolayers. The LYZ/g-C3N4 could quickly re-form a uniform aqueous dispersion solution after freeze-drying, and exhibit good stability. Further, the results of photocatalytic sterilization showed that the assisted dispersion of LYZ enhanced the bactericidal activity of g-C3N4 and exhibited promising application prospects in the field of biomedicine and water disinfection.

Exfoliation of graphitic carbon nitride and homogeneous loading of Cu2O catalyst

In order to get desired Cu2O catalyst on two-dimensional (2D) g-C3N4, bulk melamine-derived g-C3N4 with a very small specific surface area was exfoliated first and then Cu2O catalyst was loaded using solvothermal method. X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Electrochemical impedance spectroscopy (EIS), N2 adsorption/desorption and Fourier transform infrared (FT-IR) techniques as well as catalytic evaluation were performed to investigate the structure-properties relationship of the composite catalyst. The results show that the as-prepared Cu2O catalyst with the exfoliated g-C3N4 as support not only exhibits a uniform dispersion of Cu2O nanoparticles with ultrafine particle size, but also inherits a large specific surface area up to 165.3 m2/g that hasn't been reported before for transition metal oxide being supported on 2D g-C3N4 with high loading, in the meantime improved catalytic performance towards the removal of some organic pollutants is obtained.

In-situ exfoliation of graphitic carbon nitride with metal-organic framework via a sonication-assisted approach for dispersive solid-phase extraction of perfluorinated compounds in drinking water samples

Monitoring the levels of perfluorinated compounds (PFCs) in the environment is of vital importance, owing to their sustained environmental presence, extensive distribution, and associated health risks. The development of cost-effective and efficient sorbents for the establishment of sensitive analytical methods is critical for achieving trace-level detection. In this study, a graphitic carbon nitride (g-C3N4)-based sorbent is synthesized by a facile sonication-assisted method exfoliated by zeolitic imidazolate framework-67 (ZIF-67) in situ. The novel ZIF-67/g-C3N4 composites were systematically characterized by transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and N2 adsorption–desorption analysis, exhibiting good dispersity and a large surface area. Moreover, molecular dynamics simulations indicated that g-C3N4 structures can be effectively exfoliated by the introduced ZIF-67 molecules. The hybrid material was successfully utilized as a dispersive solid-phase extraction sorbent, and the extraction factors were systematically optimized by response surface methodology. Under optimal conditions, the synthesized sorbent exhibited desirable linear correlations (R2 > 0.99), a low detection limit (0.3–2 ng L−1), and good repeatability (relative standard deviation <15%, n = 6). The developed method was applied for the analysis of natural and spiked water samples. The study demonstrated that the ZIF-67/g-C3N4 composites are promising materials for pollutant adsorption from drinking water samples.

Gas exfoliation of graphitic carbon nitride to improve the photocatalytic hydrogen evolution of metal-free 2D/2D g-C3N4/graphdiyne heterojunction

Abstract Metal-free photocatalysts have received increasing attention as nonmetal elements are abundant in the earth and friendly to the environment. Graphitic carbon nitride (g-C3N4) as a typical two-dimensional (2D) metal-free photocatalysts for water splitting has attracted increasing interest due to its economic production and environmentally friend features. However, the high photocarriers recombination rate constraint its catalytic activity. Combining the single- or few-layered g-C3N4 nanosheets with other 2D functional materials to form efficient metal-free heterojunction photocatalysts is one of the effective strategies to improve the photocarriers separation. Herein, we introduce a simple and efficient method to scalable preparation few-layered g-C3N4 nanosheets using gas exfoliation of bulk g-C3N4 in liquid nitrogen. Then we introduce the g-C3N4 nanosheets into construct a 2D/2D heterojunction of g-C3N4/graphdiyne by π-π interaction, where graphdiyne (GDY) as a new 2D carbon allotrope, has excellent holes transfer nature. We find that the 2D/2D g-C3N4/GDY photocatalyst with 1% GDY is the optimum condition, with the highest H2 evolution rate of 454.28 μmol h−1. The superior photocatalytic performance may be attributed to the excellent photocarriers separation in g-C3N4 under the built-in field, where GDY can rapid transport holes from g-C3N4 to the sacrificial agents.

Sugar-assisted mechanochemical exfoliation of graphitic carbon nitride for enhanced visible-light photocatalytic performance

A simple co-grinding treatment with fructose is introduced for the efficient and scalable preparation of g-C3N4 nanoplates. The results revealed that these g-C3N4 nanoplates still preserved the basic framework of carbon nitride and even displayed superior morphological properties and electronic structures. With respect to the pristine carbon nitride, the few-layered g-C3N4 impressively demonstrated an enhanced photocatalytic activity towards hydrogen generation and the degradation of Rhodamine B (RhB) under visible light illumination, emphasizing the vital roles of the morphology and electronic structures on the photocatalytic performance. This study provided sustainable and cost-effective tactics for the delamination of g-C3N4 for efficient energy conversion.

Ultrasonic-Assisted Exfoliation of Graphitic Carbon Nitride and its Electrocatalytic Performance in Process of Ethanol Reforming

Graphitic carbon nitride was synthesized via thermolysis of urea and then ultrasonic exfoliated from colloidal solution to obtain phase pure ultrafine powder of g-C3N4. It was shown that ultrasonic-assisted exfoliation of the initial graphitic carbon nitride powder leads to an increase in its phase purity (PXRD), a change in the morphology (SEM), a decrease in the band gap from 2.93 eV to 2.85 eV (DRS) and an increase in the specific surface from 58.6 m2/g to 136.7 m2/g (BET). In addition, it was found that the exfoliated g-C3N4 is an effective catalyst for the process of electrocatalytic reforming – the hydrogen evolution from the water-alcohol solution. Based on volamperometry, it was found that the hydrogen overpotential of graphitic carbon nitride is equal to 249 mV (at 10 mA/cm2), and the Taffel slope is 112 mV/dec. The results of cyclic voltammetry of the electrode based on exfoliated g-C3N4 indicate its high stability, which allows us to consider the exfoliated graphitic carbon nitride as a promising basis of materials for electrocatalytic reforming of alcohols.

Green exfoliation of graphitic carbon nitride towards decolourization of Congo-Red under solar irradiation

Exfoliated g-C3N4 nanoparticles were synthesized by the aqueous bi-thermal methods and were evalute during different analytical tools and techniques like XRD, PL, FTIR, UV–vis-DRS, FESEM, and HRTEM etc. The exfoliated g-C3N4 obtained using this green exfoliation technique provided material with improved band gap. The results of UV-VDRS spectrophotometer together with Mott-Schottky graphs of exfoliated g-C3N4 nanoparticles corroborated this observation. The sought after characteristics like effective separation and very low rate of recombination of photo-induced electron and holes and enhanced band-gap of exfoliated g-C3N4 are expected to increase the photocatalytic performance of semiconductor. The photo catalytic ability of the exfoliated g-C3N4were evaluated from solar decolourization studies of 100 ppm aqueous solution of Congo-Red (CR).The decolourization up to 95.1% could be achieved with 1 h exposure to sun light at catalyst concentration of 1 g/L. The experiments included scavenger tests for active species identification and prediction of CR decolourization mechanism. This project demonstrates a low cost, green method for exfoliation of g-C3N4 scalable further.

Porous graphitic carbon nitride nanoplates obtained by a combined exfoliation strategy for enhanced visible light photocatalytic activity

The facile exfoliation of graphitic carbon nitride (g-C3N4) into single- or few-layered nanoplates remains a grand challenge for the fundamental studies and applications of g-C3N4. Herein, we present an efficient tactic for the facile fabrication of few-layered porous g-C3N4 nanoplates using a novel combination of thermal etching and gas-driven exfoliation of bulk g-C3N4. In comparison with the pristine g-C3N4, the few-layered porous g-C3N4 nanoplates displayed modified electronic structures and large specific surface area. Consequently, the obtained g-C3N4 nanoplates after the several exfoliation cycles showed greatly enhanced photocatalytic activities. The average hydrogen (H2) evolution rate of g-C3N4 nanoplates exceeds that of the bulk counterpart by almost 9 times and the photodegradation efficiency of rhodamine B (RhB) increased by about 6-fold under visible light irradiation. Our work provides an efficient method towards the fabrication of porous g-C3N4 nanoplates with impressive photocatalytic performance.

Exfoliation of Graphitic Carbon Nitride for Enhanced Oxidative Desulfurization: A Facile and General Strategy

A series of graphitic carbon nitride (CN) in the form of nanosheets with porous structure have been prepared through thermal treatment of bulk CN in air. Compared with the bulk counterpart, the as-generated holey CN nanosheets are larger in specific surface area. Endowed with more active sites and enhanced mass transport ability, the latter display catalytic performance substantially superior to the former, exhibiting higher H2S conversion and S selectivity in the oxidation of H2S to S. Moreover, the CN nanosheets show much better durability than traditional catalysts. It is envisaged that the strategy is a general technique that can be extended to produce porous CN nanosheets from other nitrogen-rich precursors, as well as to prepare other 2D carbon-based materials for potential applications.

Filling foaming agent into stacked layers: Rapid synthesis of graphitic carbon nitride nanosheets decorated with ultrafined MXY (X = O, S) nanoparticles for enhanced photoresponsive abilities

Exfoliation of graphitic carbon nitride (g-C3N4) into ultrathin nanosheets is usually the first step for its perspective applications. In contrast to the traditional time-consuming ultrasonication approach, a rapid and high-yield method to synthesis g-C3N4 nanosheets is desirable. In this study, we develop an efficiency and versatile strategy to exfoliate bulk g-C3N4 into 2D ultrathin nanosheets by combining foaming agent inserting with microwave digestion method. The proposed method significantly reduces the exfoliation time and can be further utilized to produce metal oxides (MOY) or metal sulfide (MSY) decorated g-C3N4 nanosheets. The as-formed ultrafined ZnO nanocrystals decorated g-C3N4 nanosheets (ZnO/g-C3N4) exhibit excellent solubility and dual-emission optical property, which can be served as fluorescence probes for metal ion sensing. The resulted CdS/g-C3N4 decorated nanosheets demonstrate efficient photocatalytic properties, having great potentials in photodegradation application. This protocol can be a general strategy for the synthesis of g-C3N4 nanosheets as well as attractive in preparing a lot of functional hybrid nanosheets for future applications in sensing probes, solar cells, photoelectrical devices and water treatment.

A new bifunctional nanostructure based on Two-Dimensional nanolayered of Co(OH)2 exfoliated graphitic carbon nitride as a high performance enzyme-less glucose sensor: Impedimetric and amperometric detection

A novel non-enzymatic glucose sensor was constructed based on the nanolayered Co(OH)2 deposited on polymeric graphitic carbon nitride (Co(OH)2-g-C3N4) via chemical bath deposition. The two-dimensional nanocomposite was used to modify a carbon paste electrode and its electrochemical performance of electrode was carefully evaluated. The electrochemical oxidation of glucose at modified electrode was studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 0.2 M KOH. It revealed a remarkable electrocatalytic behavior and noticeably synergistic effect as a result of decent exfoliation of graphitic carbon nitride in the presence of Co(OH)2. The amperometric response achieved by the modified electrode showed two calibration ranges with an excellent selectivity. A single-frequency impedance method was applied for glucose determination as an alternative to conventional EIS methods. The developed sensor represents a high sensitivity, wide concentration range (25 μM - 420.0 mM by impedimetry and 6.6–9800 μM by amperometry), and high reproducibility. The modified electrode showed a good selectivity for glucose over potentially interfering materials such as dopamine, ascorbic acid, urea, and uric acid. Finally, the Co(OH)2-g-C3N4-CPE was utilized for quantification of glucose in blood serum samples.

Graphene quantum dots-assisted exfoliation of graphitic carbon nitride to prepare metal-free zero-dimensional/two-dimensional composite photocatalysts

The high aspect-ratio morphology of two-dimensional (2D) nanostructures endues them with distinct advantages for photocatalytic or photoelectrical applications. Although various attempts have been devoted to the liquid exfoliation of graphitic carbon nitride (g-C3N4) to obtain ultrathin nanosheets (CNNSs), the high exfoliation efficiency, well preservation of in-planar structure and facile operation cannot be simultaneously realized. Furthermore, functionalization of CNNSs is highly desired to promote the capability of photoabsorption, charge separation and transfer. Herein, we one-step prepared well-dispersed graphene quantum dots (GQDs)-modified CNNSs (GQDs/CNNSs) colloids via a facile and efficient GQDs-assisted exfoliation approach in a normal ultrasonic water bath. The exfoliation procedure was optimized by tuning the dopant in GQDs, ultrasonic time and GQDs dosage. The obtained colloidal GQDs/CNNSs show a typical 2D morphology with lateral size of several 100 nm and ultrathin thickness of 1.5–1.8 nm. What is more, we can tailor the semiconductive behavior of GQDs by heteroatom doping and achieve a p–n-type P-doped GQDs-modified CNNSs colloids. This p–n GQDs/CNNSs material presents the enhanced separation efficiency of photoexcited carriers and photocatalytic activity in comparison with bulky g-C3N4 (CN) and other CNNSs materials from acid or alkali exfoliation.

Scalable and clean exfoliation of graphitic carbon nitride in NaClO solution: enriched surface active sites for enhanced photocatalytic H2 evolution

The challenge of exfoliation of bulk g-C3N4 into nanosheets was tackled using green drinking-water disinfectant NaClO in solution.

Scalable and super-stable exfoliation of graphitic carbon nitride in biomass-derived γ-valerolactone: enhanced catalytic activity for the alcoholysis and cycloaddition of epoxides with CO2

γ-Valerolactone could exfoliate bulk g-C3N4 to form a super-stable dispersion of few-layer g-C3N4 nanosheets with a high concentration of 0.8 mg mL−1, showing enhanced activity for non-photocatalytic reactions.

Investigating the Dispersion Behavior in Solvents, Biocompatibility, and Use as Support for Highly Efficient Metal Catalysts of Exfoliated Graphitic Carbon Nitride.

The liquid-phase exfoliation of graphitic carbon nitride (g-C3N4) to afford colloidal dispersions of two-dimensional flakes constitutes an attractive route to facilitate the processing and implementation of this novel material toward different technological applications, but quantitative knowledge about its dispersibility in solvents is lacking. Here, we investigate the dispersion behavior of exfoliated g-C3N4 in a wide range of solvents and evaluate the obtained results on the basis of solvent surface energy and Hildebrand/Hansen solubility parameters. Estimates of the three Hansen parameters for exfoliated g-C3N4 from the experimentally derived data yielded δD ≈ 17.8 MPa(1/2), δP ≈ 10.8 MPa(1/2), and δH ≈ 15.4 MPa(1/2). The relatively high δH value suggested that, contrary to the case of other two-dimensional materials (e.g., graphene or transition metal dichalcogenides), hydrogen-bonding plays a substantial role in the efficient interaction, and thus dispersibility, of exfoliated g-C3N4 with solvents. Such an outcome was attributed to a high density of primary and/or secondary amines in the material, the presence of which was associated with incomplete condensation of the structure. Furthermore, cell proliferation tests carried out on thin films of exfoliated g-C3N4 using murine fibroblasts suggested that this material is highly biocompatible and noncytotoxic. Finally, the exfoliated g-C3N4 flakes were used as supports in the synthesis of Pd nanoparticles, and the resulting hybrids exhibited an exceptional catalytic activity in the reduction of nitroarenes.

Spectral and Luminescent Characteristics of Products from Exfoliation of Graphitic Carbon Nitride Produced at Various Temperatures

It was shown that graphitic carbon nitride (CN) produced at 500–725 °C can be exfoliated in aqueous solutions of tetraethylammonium hydroxide with the formation of stable colloids characterized by photoluminescence (PL) in the visible region of the spectrum. It was established that increase of temperature leads to decrease of the intensity of PL until it disappears completely at T > 675 °C. In the case of exfoliated CN the intensity of PL increases sharply with increase of temperature. This may be due to decrease in the size of the colloidal particles of CN, to the dynamics of internal conversion of electronic excitation in colloidal CN, and to the removal of peroxy groups from the core of the bulk CN in the course of exfoliation.