Graphitic Carbon Nitride Composites Research Articles

Degradation of Methyl Red (MR) dye via fabricated Y2O3–MgO/g-C3N4 nanostructures: Modification of band gap and photocatalysis under visible light

In this study, graphitic carbon nitride (g-C3N4) composites with metal oxide nanoparticles (Y2O3, MgO) and their combination (CN, YCN, MCN and YMCN) were synthesized by an ultrasonic technique and were then characterized by different tools such as UV–Vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS). From the XRD diffractograms of the YMCN ternary composite, the g-C3N4, cubic MgO and Y2O3 structural phases were identified. The morphology of the as prepared nanostructure from the SEM analysis revealed the dispersion of the metal oxides nanoparticles with the graphitic sheets and the presence of the corresponding elements were confirmed by the EDX and XPS data. The FT–IR bands confirmed the bonding of the metal oxides to the nitride host as indicated by the characteristic modes. A reduction of the band gap energies was confirmed by the UV–Vis to indicate its visible light possible photoactivity. Accordingly, its visible light driven photocatalytic performance was assessed for methyl red degradation. The degradation competence was highest for the ternary composite YMCN due to the coupling of the semiconductors which increases the absorption and the charge carriers’ separation as well. The kinetics of degradation was best described by pseudo-first-order, and the most active species were the holes and the hydroxyl radicals. Thus, the YMCN nanocomposite is a visible light-active photocatalyst which can be engaged in the degradation of organic pollutants.

One pot synthesis of multi-functional B doped g-C3N4-praseodymium oxide nanocomposites for colorimetric detection of Hg2+ ion and solar photocatalytic removal of toxic water pollutants

A novel praseodymium oxide-boron co-doped graphitic carbon nitride composite was synthesized via one-step solid-state thermal condensation of urea, orthoboric acid and praseodymium nitrate precursors. The prepared composites were characterized by various methods. All the prepared composites demonstrated multi-functional activities towards peroxidase-mimetic based colorimetric detection of Hg2+ ions and superior photocatalytic efficiency towards photodegradation of textile colorants, photoreduction of hexavalent chromium and nitro aromatics like para-nitro phenol (PNP) and para-nitro aniline (PNA). The superior photocatalytic activity can be attributed to the formation of type II heterojunction which facilitates charge separation and increases the lifetime of photogenerated charge pairs. As evident from the scavenger studies, these charge pairs are involved in the formation of superoxide and hydroxyl radicals. The superior activity of the optimum composite can be attributed to the porous flaky morphology, decreased optical band gap, heterojunction mediated charge separation, and praseodymium oxide's conductive nature. A linear range of about 0.25–800 nM of Hg2+ ions can be detected with a limit of detection (LOD) of 42.4 nM using the colorimetric strategy. The as-synthesized composite is thus a unique, efficient, economically viable, and excellent candidate for detecting and degrading various hazardous water pollutants.

Photo-induced CO2 cycloaddition and tetracycline degradation over novel FeOx modified defective graphitic carbon nitride composite

Utilizing sunlight to achieve CO2 conversion and environmental remediation has been a key focus. Herein, “all-in-one” graphitic carbon nitride (g-C3N4) composite-based photocatalysts were synthesized by a simple one-step low-temperature calcination. Lower calcination temperature resulted in defective g-C3N4 enriched in cyano and hydroxyl groups. It was found that by incorporating amorphous FeOX, the resulted FeOX/O-g-C3N4 photocatalyst shows very good performance towards both CO2 cycloaddition reaction and photo-Fenton degradation of tetracycline (TC). It was also found that the photocatalyst shows the highest styrene carbonate yield of 83% (23 mmol g−1 h−1) under ambient conditions, which is 13.8 times higher than that obtained over pure g-C3N4. The photocatalyst also exhibits a 4.7 times faster TC removal rate than that of pure g-C3N4. Systematic characterization and mechanism study demonstrate the role of defects and photo-induced charge carriers.

Synthesis and Characterization of Silver Vanadate and Graphitic Carbon Nitride Composites

Various silver vanadate and graphitic carbon nitride (AgVA/g-C3N4) composites with different weightage of 10 wt%, 30 wt% and 50 wt% of AgVA were synthesized using wet chemical method and the prepared samples were named as A10, A30 and A50. Based on SEM analysis, the synthesized pure g-C3N4 exhibited a two-dimensional structure with typical irregular porosity whereas pure AgVA had a rod-like shape. The diffraction peaks of both g-C3N4 and AgVA could be observed in the composites, indicating that AgVA had been successfully coupled with g-C3N4. The stretching vibration of V-O was found in in pure AgVA and all composites. EDX analysis confirmed the presence of C, N, Ag, V and O element in the prepared composites. A10 was found to possess a larger BET specific surface area, smaller particle size and larger pore volume compared to that of pure g-C3N4.

Synthesis of graphitic carbon nitride-based nanocomposites and their mechanical properties in epoxy compositions.

Thermoset epoxy resins are widely used in research and commercial applications. Zeolite imidazole framework-8 (ZIF-8), graphitic carbon nitride (GCN, g-C3N4), and S-doped graphitic carbon nitride (SCN, S-g-C3N4) composites were synthesized as accelerators and their effects on the physical properties of epoxies were examined. An ultrasound-assisted method was used to prepare ZIF-8/GCN and ZIF-8/SCN nanocomposites while g-C3N4 and S-g-C3N4 were prepared from the calcination of melamine and thiourea, respectively. The surface morphology, and particle size were characterized by scanning electron microscopy, and X-ray diffraction. The properties of synthesized nanocomposites were measured using Fourier-transform infrared spectroscopy. After the accelerator was added to the epoxy composites, their activation energies were calculated using differential scanning calorimetry. The tensile strength and flexural strength were measured using a universal testing machine and impact strength was measured by using an Izod impact strength tester. The impact strength of ZIF-8/SCN nanocomposites was enhanced by 45.2%. The storage stability of the epoxy compositions with different catalysts was evaluated by measuring the variation of viscosity with time at a constant temperature.

Box–Behnken design in optimizing heavy metal removal from wastewater using selenium hybridized graphitic carbon nitride nanocomposites

In this study Box–Behnken designs and response surface methodology (BBD-RSM) was used for optimizing heavy metal adsorption. The hazardous effect of wastewater on agriculture, animals and human as well makes its remediation is being considered a global challenge. Herein, a novel visible-light-responsive selenium-doped graphitic carbon nitride composites via the exfoliation of g-C3N4 polymer with different concentrations of selenium precursor (1 w%, 2.5 w%, 5 w%, with respect to the weight of g-C3N4) under ultrasound irradiation condition to produce the hybridized the corresponding polymeric nanocomposites (5%Se/g-C3N4), (10%Se/g-C3N4) and (25%Se/g-C3N4) denoted names C1, C2, C3; respectively. Full chracterization for the nanocomposites was performed using scanning electron microscope (SEM), X-ray diffraction (XRD), UV–Vis diffuse reflection spectroscopy. The as-prepared nanocomposites compared to pure g-C3N4 were applied in wastewater treatment for a real sample collected from Siwa Lake that suffered from increasing the heavy metal ions due to industrial drainage. Testing the catalytic activity of the prepared composites in treatment of wastewater sample collected from Siwa Lake in Egypt affected by the industrial drainage that was analyzed to determine the occurred polluted heavy metal ions. It was indicated that this sample contained Ca(II), Zn(II), Fe(II), Cu(II), Mn(II) and Cd(II) ions. The metal adsorption measurements were developed using atomic absorption spectroscopy (AAS) to show the removal efficiency of metal ions.

Preparation and enhanced photocatalytic performance of N-TiO2/g-C3N4 heterostructure for Rhodamine B degradation

Highly efficient photocatalysts have been developed for the degradation of contaminated water under visible light. In this study, N-doped TiO2 (N-TiO2) and metal-free graphitic carbon nitride (g-C3N4) composites with various Ti/C molar ratios were prepared with the simple mixing-calcining method. The samples were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The photocatalytic activity of N-TiO2/g-C3N4 in the degradation of Rhodamine B (RhB) was investigated, and the electrochemical method was used to determine the origin of the enhanced photoactivity of N-TiO2/g-C3N4. The results showed that N-TiO2 nanoparticles were dispersed on the surface of g-C3N4 and formed a stable heterojunction structure with g-C3N4. The heterojunction between the two semiconductors could effectively prevent the recombination of photogenerated electrons and holes and improve the photocatalytic efficiency of the photocatalyst under visible light irradiation. The photocatalyst exhibited high stability, and the RhB degradation rate was still higher than 82.3% after five cycles.

ZnO nanoparticles dispersed in nitrogen-enriched carbon matrix for the efficient adsorption and photocatalytic degradation of aqueous methylene blue molecules

In the present study, ZnO nanoparticles dispersed in graphitic carbon nitride (g-C3N4) composite is synthesized via hydrothermal route at 150 °C. The synthesized material (ZnO/g-C3N4) is further heat-treated at an optimized temperature of 500 °C in an air-rich environment and the heat-treated material is denoted as the ZnO/g-C3N4-HT. Physicochemical properties of the as-synthesized material are evaluated by various analytical and spectroscopic techniques. The obtained results confirm good dispersion of the ZnO nanoparticles on the surface of the g-C3N4. The ZnO/g-C3N4-HT is further tested for its adsorption ability and photocatalytic activity towards aqueous methylene blue (abbreviated as MB). The data show that the ZnO/g-C3N4-HT possesses remarkably high MB adsorption capacity of 251.70 mg/g at the pH value of 7. The MB adsorption capacity obtained in the present study is superior to most of the carbon-based adsorbents. The kinetic curve is found to be in good agreement with pseudo-second-order kinetic model. The remarkably high MB adsorption capacity is ascribed to the combined effects of surface area, wettability characteristic, and the negative surface charge of the material. The photocatalytic MB-degradation study over the ZnO/g-C3N4-HT yields a maximum degradation efficiency of 90% with pseudo-first-order rate constant value of 0.0113 min−1. The high MB-degradation efficiency of the material is attributed to the modified band gap and morphological properties of the material. With adequate optimization, the ZnO/g-C3N4-HT may be useful in the removal of several other recalcitrant organic pollutants from water.

Mesostructured graphitic carbon nitride composites with silver nanoparticle decoration as the best visible-light-driven photocatalysts for dye degradation and H2 production

Water-splitting photocatalysis on the surface of semiconductors has emerged as a promising approach for wastewater treatment to remove organic pollutants from aqueous media in various industrial fields. However, developing efficient photocatalysts with sufficient activity is challenging owing to the rapid recombination of photogenerated electrons and holes in the available functional materials. Aiming to fabricate photocatalysts to remove pollutants with reduced electron-hole recombination, mesostructured graphitic carbon nitride (MCN) composites made of Ag-doped melamine were designed and synthesized at room temperature. The structural and optical properties of the prepared MCN composite indicate that it is well-suited for use as a visible-light-driven photocatalyst. A morphological analysis using transmission and scanning electron microscopy showed that the Ag nanoparticles were uniformly distributed on the surface of the MCN sheets, promoting the photocatalytic property of the Ag/MCN composites. Adding silver nanoparticles onto MCN facilitates the rapid transfer of photo-generated electrons from MCN to the silver nanoparticles. This is due to the presence of an interfacial electric field across the junctions, leading to a reduction in the recombination process, resulting in superior photocatalytic activity in the degradation of reference organic pollutants like methylene blue and crystal violet, more than 96% of degradation was achieved in the presence of the MCN\\Ag-MCN composite. An astonishing photocatalytic hydrogen evolution rate of 5.24 mmol. g−1.h−1 was observed for the optimized MCN/Ag-MCN nanocomposite.

Cobalt molybdate hollow spheres decorated graphitic carbon nitride sheets for electrochemical sensing of dimetridazole

In the present work, a cobalt molybdate (CoMoO4) hollow spheres-incorporated graphitic carbon nitride (g-CN) composite is prepared for the electrochemical detection of dimetridazole (DZ). The synergistic effect between the hollow-structured CoMoO4 and g-CN nanosheets facilitates the transportation of electrons through kinetic barriers, thereby providing a high electrical conductivity with increased electroactive sites. The proposed CoMoO4@g-CN-modified electrode displayed a wide linear range (0.001–492.77 μM) and a lower detection limit (LOD: 0.4 nM) for the determination of DZ through the amperometry (i–t) method. In addition, the CoMoO4@g-CN-modified electrode achieved good operational stability, anti-interfering ability (five-fold excess amount of co-interfering compounds) and reproducibility. These results demonstrate the increased electrocatalytic activity of CoMoO4@g-CN modified glassy carbon electrode (GCE) towards the detection of DZ in food samples with satisfactory recovery ranges.

Photocatalytic hydrogen under visible light by nitrogen-doped rutile titania graphitic carbon nitride composites: an experimental and theoretical study

Photocatalytic hydrogen under visible light by nitrogen-doped rutile titania graphitic carbon nitride composites: an experimental and theoretical study

Visible-light-assisted activation of peroxymonosulfate (PMS) over CoOx @C/g-C3N4 composite for efficient organic pollutant degradation

As a promising advanced oxidation process, photo-assisted peroxymonosulfate (PMS) activation for wastewater treatment has attracted widespread attentions. However, rational design of synergetic and recyclable catalysts for PMS photo-activation remains a big challenge. In this study, a carbon layer-coated amorphous CoOx supported on graphitic carbon nitride (CoOx @C/g-C3N4) composite was fabricated to drive visible-light-assisted activation of PMS for efficient organic pollutant degradation. Amorphous CoOx nanoparticles were in-situ grown on two-dimensional g-C3N4 substrate, among which a carbon layer serves as a high-speed electron transmission channel, facilitating the separation of photogenerated electron-hole pairs and accelerating the Co3+/Co2+ redox cycle. Simultaneously, the carbon layer provides a protective film to suppress Co leaching, thereby improving the catalytic activity and reusability. Owing to the unique heterostructure and synergetic effect, the optimized 6% CoOx @C/g-C3N4 composite exhibits superior catalytic efficiency and excellent cycling stability towards the degradation of various organic pollutants, which displays nearly 100% elimination of tetracycline (TC) within 80 mins. The h+, SO4•- and •OH are determined as the main contributors in the visible light-assisted PMS activation system, and the possible catalytic mechanism is also proposed. This work demonstrates a feasible strategy for constructing synergetic and effective photo-activation PMS catalysts for water remediation.

The environmentally friendly approaches based on the heterojunction interface of the LaFeO3/Fe2O3@g-C3N4 composite for the disposable and laboratory sensing of triclosan.

Triclosan (TCS) is a polychlorinated phenoxy phenol (PCPPs) used as a disinfectant and a broad-spectrum antibacterial and antifungal agent in personal hygiene products. TCS easily forms diphenyl ethers and dioxins, which are persistent organic pollutants. This work used a double approach for the TSC sensing: a) screen-printed (SPE) electrochemical platform for on-site application, modified with lanthanum iron oxide and graphitic carbon nitride composite (LaFeO3/Fe2O3@g-C3N4/SPE); and b) carbon paste electrode (CPE), modified with the same material and used in laboratory conditions. Linear range from 0.1 μM to 10 μM, the limit of detection (LOD) of 29 nM and the limit of quantification (LOQ) of 91 nM were obtained for CP electrode in BRBS pH 8. SPE showed the best analytical parameters in BRBS at pH 3, with a linear range from 0.3 μM to 7 μM, LOD of 0.09 μM and LOQ of 0.28 μM. Furthermore, the influence of potential interferents was investigated and proven to be negligible. Determination of TSC was performed to estimate the environmental impact of this compound as well as the practical usefulness of the proposed sensor in the real sample analysis, confirmed with a HPLC analysis.

RuO2 nanoparticles anchored on g-C3N4 as an efficient bifunctional electrocatalyst for water splitting in acidic media.

The electrolysis of water, particularly proton exchange membrane (PEM) water electrolysis, holds great promise for hydrogen production in industry. However, the catalyst used in this process is prone to dissolution in acidic environments, making it imperative to develop cost-effective, highly efficient, and acid-stable electrocatalytic materials to overcome this challenge and enable large-scale application of PEM water electrolysis technology. Herein, we prepared ruthenium oxide (RuO2)/graphitic carbon nitride (g-C3N4) composites (RuO2/C3N4) via a combination of sol-gel and annealing methods. The g-C3N4 provides a large surface area, while RuO2 is uniformly deposited on the g-C3N4 surface. The interaction between g-C3N4 and RuO2 stabilizes the RuO2 nanoparticles and enhances long-term water oxidation stability. This unique structure and the combined advantages of RuO2 and g-C3N4 yield exceptional electrocatalytic activity toward both the oxygen evolution reaction (OER, 240 mV@10 mA cm-2) and the hydrogen evolution reaction (HER, 109 mV@10 mA cm-2), with excellent durability (over 28 h), and a cell voltage of 1.607 V at 10 mA cm-2 when used in an RuO2/C3N4||RuO2/C3N4 electrolyzer. This study highlights the efficacy of the g-C3N4 support method in designing highly stable Ru-based OER electrocatalysts for efficient acidic water splitting.

Enhanced Room-Temperature Ethanol Detection by Quasi 2D Nanosheets of an Exfoliated Polymeric Graphitized Carbon Nitride Composite-Based Patterned Sensor.

A novel room-temperature gas sensor composed of polymeric graphitic carbon nitride composite was fabricated and used for the detection of ethanol vapor under ambient conditions. Polymeric carbon nitride (PCN) microstructures composed of fluffy nanosheets were synthesized via a thermal polycondensation mechanism using melamine as the precursor, followed by vigorous chemical exfoliation. These sheet-like microstructures were employed as active materials in the form of composites, along with carbon paste consisting of graphite nanoplatelets and carbon black. The active sensing layer was fabricated on a PET sheet and assembled on an interdigitated gold electrode. The as-fabricated sensor exhibited excellent sensing efficiency (>100% response at 10 ppm) along with high selectivity and stability. In particular, for ultralow concentrations such as 1 ppm (>10% response), this resistive-based sensor exhibited a swift response time provided under ambient conditions. The exfoliated PCN composite sensor was found to be working with appreciable efficiency at moderate relative humidity (%) with the least fluctuation in response signals also demonstrating long-term stability for 30 days with consistent response signals.

DFT based comparative study of pristine gCN and gCN-ZnO composite as a sensor for CO and CO2 gases

• Graphitic carbon nitride and ZnO composite (gCN-ZnO) is reported for CO and CO 2 sensing. • CO and CO 2 shows strong interaction with gCN-ZnO composite as compare to pristine gCN. • Adsorption energy for gCN-ZNO is −11.03 eV and −16.61 eV for CO and CO 2 respectively. • The adsorption energy for gCN-ZnO composite are 8 times (CO) and 12 times more (CO 2 ) than pristine gCN. In the present study sensing behavior of pristine gCN and gCN-ZnO composite towards CO and CO 2 gases has been analyzed using DFT. Structural and electronic properties such as adsorption energy, band structure and density of states (DOS) have been investigated. The study reveals that the sensing performance of gCN is enhanced by incorporating ZnO and hence gCN-ZnO composite is a better material for CO and CO 2 gas sensing.

Graphitic Carbon Nitride Composites with Gold and ZIF-67 Nanoparticles as Visible-Light-Promoted Catalysts for CO2 Conversion and Bisphenol A Degradation

Graphitic Carbon Nitride Composites with Gold and ZIF-67 Nanoparticles as Visible-Light-Promoted Catalysts for CO₂ Conversion and Bisphenol A Degradation

Synthesis of rGO/g-C3N4 for methyl orange degradation in activating peroxydisulfate under simulated solar light irradiation

• Metal-free rGO/g-C 3 N 4 composite was synthesized successfully by a simple polymerization-hydrothermal method. • rGO/g-C 3 N 4 /PDS system exhibited superior degradation efficiency of MO under stimulated solar light irradiation. • SO 4 ¯ · , h + , O 2 ¯ · and non-radical reaction pathway were involved in the removal of MO. In this study, reduced graphene oxide-based graphitic carbon nitride (rGO/g-C 3 N 4 ) composite was fabricated via thermal polymerization-hydrothermal method and were utilized to activate peroxydisulfate (PDS) under simulated solar light irradiation. The as-synthesized rGO/g-C 3 N 4 was demonstrated to effectively remove methyl orange (MO) in wastewater. Notably, 92.3% of MO (15 mg/L) was removed within 120 min in the presence of 0.2 g/L rGO/g-C 3 N 4 and 0.225 g/L PDS. The influence of activator dosage, PDS concentration and co-existing solution matrix on the removal efficiency was investigated. Free radical capture experiments confirmed that SO 4 ¯ · , photogenerated holes (h + ), O 2 ¯ · and non-radical reaction initiated by rGO played a major role in MO removal. Furthermore, PDS and rGO acted as the electron acceptor and transfer carrier of the photogenerated charges, respectively, resulting in the efficient activation of PDS. The promoting visible light absorption might be ascribed to the defect sites on the surface of rGO/g-C 3 N 4 , which generated from the rGO loading. This study revealed that the as-synthesized rGO/g-C 3 N 4 composite exhibits wide promising application prospects as a photocatalytic activator of PDS for the degradation of azo dyes in textile wastewater.

Photocatalytic performance of alkali metal doped graphitic carbon nitrides and Pd-alkali metal doped graphitic carbon nitride composites

Although there are several reports about the beneficial performance of metal doped graphitic carbon nitrides (g-C3N4) in various photocatalytic reactions, the effect of different alkali metal dopants has not been studied systematically. Series of undoped, Li-, Na- and K-doped samples was synthetized and used for the preparation of novel type of photocatalysts, composed of palladium nanoparticles supported on alkali metals-doped graphitic carbon nitride. Palladium loading was achieved via citrate reduction of palladium precursor in the presence of the carbon nitride material. Several physicochemical characterization methods such as attenuated total reflection infrared-(ATR-IR), diffuse reflectance UV–visible spectroscopy, high-resolution transmission microscopy (HRTEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), and thermogravimetric analysis (TGA) were used to get information about the morphology and composition of the novel composites. According to the optical characterization results, the band gap of g-C3N4 decreased upon Na- and K doping but increased after Li-doping. The palladium nanoparticles were distributed over the support and appeared in dispersed (undoped g-C3N4, Li-g-C3N4) or agglomerated (Na-g-C3N4, K-g-C3N4) form with individual particle size below 5 nm. The catalytic performance of these composite materials was tested in two processes: (i) photodegradation of methyl orange and (ii) hydrogen production from methanol. The Na- doping of graphitic carbon nitride was found to be a key issue to enhance hydrogen production. The carbon nitride matrix was found to be stable during the photocatalytic experiments, while the Pd component underwent certain changes during the photocatalytic reforming reaction of methanol. Our results indicated that the really acting metallic Pd cocatalyst was formed mainly in situ.

Enhanced thermoelectric properties of highly conductive poly (3,4-ethylenedioxy thiophene)/exfoliated graphitic carbon nitride composites

In this study, the thermoelectric properties of as-synthesized and –exfoliated graphitic carbon nitride (g-C3N4) filled poly (3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT: PSS) were investigated. Firstly, g-C3N4 was synthesized by heating of guanidine-HCl at 550 °C and exfoliated using an ultrasonic homogenizer. Then, PEDOT:PSS was synthesized by oxidative chemical polymerization. Finally, the composites containing different weight ratios of g-C3N4 were prepared. The conductivity of pristine PEDOT:PSS increased from 11.1 Scm−1 to 722.15 Scm−1 for the composite containing 25% exfoliated g-C3N4, whereas the power factor of PEDOT:PSS increased from 0.19 μWm−1K−2 to 419.7 μWm−1K−2 for the composite containing 15% exfoliated g-C3N4. This study suggests that exfoliated g-C3N4 is a promising material to increase the electrical conductivity and power factor of PEDOT:PSS.