Properties Of g-C3N4 Research Articles

Reduction of the photogenerated electron transport path by modulating the conduction band region to achieve the highest lignin β–O–4 bond photocleavage efficiency under xenon excitation

Photocracking of lignin β–O–4 bonds is a green approach for the high-value modification of lignin. Graphitic carbon nitride (g-C3N4) that can photocleave the β–O–4 bond is presently the only stable, metal-free photocatalyst owing to the residual metal ions generated due to photocorrosion of metal sulfides. Herein, g-C3N4 with a N–C3 vacancy structure is prepared by etching site–engineering strategy based on the protection of C–N=C structure by chlorine atom. The N–C3 vacancy structure can reduce the transport path of the photogenerated electrons by tuning the conduction band (CB) region to the edge of the photocatalyst, which impedes the critical complexation of the photogenerated electron–hole pairs and enhances the photoelectric conversion efficiency five-fold. Combined with the unique chemisorption capacity (137.82 kJ/mol) of N–C3 vacancies for oxygen, the g-C3N4 photocatalysts with N–C3 vacancy structure can generate 9.6-fold higher superoxide radicals and 13-fold higher lignin β–O–4 bond photocleavage efficiency lignin compared with untreated g-C3N4. Based on the reaction enthalpy changes and free energies investigated through simulations, a route of lignin Cα–Cβ bonds being oxidized and dehydrogenated twice by photogenerated cavities is proposed for the first time. This work reveals the relation between the properties of g-C3N4 and the photocleavage efficiency of lignin β–O–4 bonds.

One-step preparation of hierarchical porous graphitic carbon nitride photocatalyst for wastewater treatment under real sunlight

Photocatalysis is a green and efficient way to handle antibiotic wastewater. However, most of the photocatalysts cannot be applied in real environments, which seriously hinders the development of photocatalysis in practical applications. In this study, we present an environmentally friendly one-step approach for fabricating g-C3N4 with hierarchical architecture by utilizing gas-phase template NH4Cl. The effects of various precursors, preparation methods, and additions of blowing agents on the structure and properties of g-C3N4 have been systematically investigated. Notably, g-C3N4 with hierarchical architecture (BSCN-3) demonstrated superior photocatalytic performance for Rhodamine B (RhB, 96.2 %, 20 min) and sulfamethoxazole (SMX, 80 %, 1 h) in comparison to both bulk g-C3N4 (BCN) and g-C3N4 nanosheets (SCN). This superior performance can be attributed to the exceptional properties of the hierarchical architecture, including its large specific surface area and enhanced capability for separating photogenerated carriers. Surprisingly, BSCN-3 exhibited remarkable performance in the degradation of dyes and antibiotics under real sunlight conditions (RhB, 95 %, 30 min, 65 mW cm−2). In addition, BSCN-3 exhibits excellent stability, with properties remaining unchanged over five consecutive cycles of degradation. This work presents a highly effective method for creating novel structured g-C3N4, which enables photocatalytic degradation of antibiotics in real environments, and greatly promotes the development of g-C3N4 for practical water treatment.

Enhanced g-C3N4 for sustainable solar degradation of 1,3-diphenylguanidine (DPG) in wastewater: Investigating the effects of precursor, temperature, and potassium doping

Sustainable methods for wastewater treatment offer promising solutions to address pressing environmental challenges. This study investigates the potential of graphitic carbon nitride (g- C3N4) as an environmentally friendly photocatalyst for wastewater treatment. The research involves the systematic exploration of various precursors (melamine, urea, and dicyanamide), different polymerization temperatures (500, 550, and 600 °C), and varying K-doping levels (1 %, 3 %, and 5 % KOH), providing valuable insights into the properties of g-C3N4. This study marks a significant advancement by reporting, for the first time, the successful degradation of 1,3-Diphenylguanidine (DPG) in wastewater. UCN-K1, a urea-derived g-C3N4 doped with 1 % KOH, displayed exceptional performance, achieving nearly 95 % DPG removal within 6 h under solar radiation and utilizing a remarkably low dose (0.1 g/L). Furthermore, the research offers a comprehensive understanding of reaction kinetics, a detailed analysis of K-doping effects, and profound insights into the degradation mechanism of DPG, including potential transformation products.

Engineering graphitic carbon nitride for next-generation photodetectors: a mini review.

Semiconductor photodetectors, as photoelectric devices using optical-electrical signal conversion for detection, are widely used in various fields such as optical communication, medical imaging, environmental monitoring, military tracking, remote sensing, etc. Compared to the conventional photodetector materials including silicon, III-V semiconductors and metal sulfides, graphitic carbon nitride (g-C3N4) as a metal-free polymeric semiconductor, has many advantages such as low-price, easy preparation, efficient visible light response, and relatively good thermal stability. In the meantime, the polymer characteristics also endow the g-C3N4 with good mechanical properties. Apart from being used for photo(electro)catalysts during the past decades, the potential use of g-C3N4 in photodetectors has attracted great research interests very recently. In this review, we first briefly introduce the structure and properties of g-C3N4 and the key performance parameters of photodetectors. Then, combining the very recent progress, the review focuses on the active materials, fabrication methods and performance enhancement strategies for g-C3N4 based photodetectors. The existing challenges are discussed and the future development of g-C3N4 based photodetectors is also forecasted.

Influence of Different Nitrogen-Enriched Precursors on the Structure and Properties of g-C3N4

Influence of Different Nitrogen-Enriched Precursors on the Structure and Properties of g-C3N4

Tailoring the band alignment and magnetic and optical properties of g-C3N4/WSe2 van der Waals heterostructures by vacancies and atomic doping

Tunable band structure and effective spatial separation of carriers are important for designing good optoelectronic devices. In this work, effects of interfacial defect including vacancies and [Formula: see text]- or [Formula: see text]-type doping on the band alignment and magnetic and optical properties of g-C3N4/WSe2 van der Waals heterostructures are systematically investigated under the premise of spin-orbit coupling density-functional theory. The results illustrate that the pristine g-C3N4/WSe2 heterostructure exhibits intrinsic type-I band alignment with a direct bandgap of 1.101 eV, and the absorption of UV-visible light can be effectively improved compared with that of isolated WSe2 and g-C3N4 monolayers. The N vacancies as well as [Formula: see text], [Formula: see text] and [Formula: see text] doping produce asymmetrical spin-up and spin-down states, bringing about the magnetization and even magnetic half-metallicity characteristics ([Formula: see text] and [Formula: see text] doping). The band edge positions of g-C3N4/WSe2 heterostructure can be also well adjusted by introducing vacancies and [Formula: see text]- or [Formula: see text]-type doping in the g-C3N4 layer, accompanied by the transition of band alignment from types I to II, which will remarkably promote the separation of photogenerated electron-hole pairs. The defective g-C3N4/WSe2 heterostructures can be considered as a promising candidate for spintronics and optoelectronic devices.

Graphitic carbon nitride nanosheets via acid pretreatments for promoted photocatalysis toward degradation of organic pollutants

Acid treatment serves as an effective engineering strategy to modify the structure of graphitic carbon nitride (g-C3N4) for enhanced metal-free photocatalysis, while their lacks a comprehensive understanding about the impacts of different acid species and acid treatment approaches on the intrinsic structure and properties of g-C3N4 and structure–activity relationships are ambiguous. Employing inorganic/organic acids including hydrochloric acid (HCl), nitric acid (HNO3), acetic acid (HAc), sulphuric acid (H2SO4), or oxalic acid (H2C2O4) as treatment acids, herein, we compare the impacts of different acid pretreatment approaches on the structure and properties of g-C3N4. Due to different acid-melamine interaction modes and the activation roles of various acids, the obtained g-C3N4 samples exhibit varied structures, physiochemical properties and photocatalytic activities. Compared with bulk graphitic carbon nitride (BCN), g-C3N4 prepared by acid pretreatment show enhanced photocatalytic performance on bisphenol A (BPA) degradation. The photocatalytic degradation rates of BPA by g-C3N4 prepared by HNO3, HAc, H2SO4, H2C2O4, or HCl pretreatment are about 2.2, 2.7, 2.8, 3.2 and 3.8 folds faster than that by BCN. HCl pretreatment proves to be the optimal approach, with the derived g-C3N4 (HTCN) showing more intact heptazine structural units, and increased specific surface area, which promote the exposure of more active sites, accelerate charge transfer, and give rise to a notable improvement in photocatalysis, eventually. Mechanistic investigations through quenching experiments and electron paramagnetic resonance (EPR) characterization unveil that superoxide ion radical (O2−) and photo-induced holes (h+) worked principally in the photodegradation reaction. This work provides new insights for the rational selection of acid types and treatment methods to synthesize metal-free carbon nitrides with improved activity for photocatalytic applications.

Heterogeneous activation of peroxymonosulfate by Cu+-decorated g-C3N4 under sunlight for degradation of organic pollutants

This article is an in-depth study of the basis of Cu+-decorated triazine-based g-C3N4 (Cu+/g-C3N4) nanosheet-activated H2O2. In this study, peroxymonosulfate (PMS) was activated by Cu+/g-C3N4 under sunlight and used to treat simulated wastewater RhB. The properties of g-C3N4 and Cu+/g-C3N4 were characterized by UV–Vis DRS and PL. The results indicated that the introduction of Cu+ in g-C3N4 can enhance the separation of photogenerated electron-hole pairs. The Cu+/g-C3N4(1:4) samples exhibited the best PMS activation performance under sunlight when 0.5 g/L catalyst dose and 0.5 mmol/L PMS concentration were used, and the removal rate of RhB reached 95.7% in 30 min. Moreover, better catalytic activity of the system can be achieved in the initial pH range of 2.0–10.0. The investigation results of the catalytic mechanisms showed that the prepared Cu+/g-C3N4 catalyst constructs a dual reaction center of Cu+/Cu2+ cycling and eCB−/hVB+ transfer for efficient PMS activation. The degradation of pollutants benefits from the participation of a variety of free radicals, which are generated by sunlight-assisted heterogeneous activation of PMS. This study has resulted in substantial progress in activating multiple oxidants with a single heterogeneous catalyst and provides a feasible way to treat refractory wastewater using Cu+/g-C3N4 with PMS under sunlight.

Oxalic acid induced defect state graphitic carbon nitride with improved photocatalytic performance

A defect state g-C3N4 was synthesized from urea by thermal condensation and oxalic acid treatment. Various analytical methods such as X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy were adopted to characterize the structures and properties of g-C3N4. The results showed that oxygen atoms replaced the carbon atoms of g-C3N4, which changed the band structure of g-C3N4. The catalytic performances of defect state g-C3N4 were improved and exhibited better photocatalytic activity than pure g-C3N4. For the effects of acetic acid concentration, g-C3N4 treated by 0.05 mol/L oxalic acid exhibited enhanced photocatalytic performance, which could be attributed to the suitable defect concentration. The photocatalytic degradation mechanism was proposed. Superoxide radicals instead of hydroxyl radicals played an important role in the rhodamine B degradation.

Photocatalytic Degradation of Pharmaceuticals through Bulk and Mesoporous g-C3N4/TiO2 Systems

Background: In recent years, pharmaceutical pollutants have emerged as a growing threat to the environment. To mitigate this situation, heterogeneous photocatalysis has been considered a promising advanced oxidation technology, where TiO2-based systems have exhibited outstanding efficiency in the degradation of organic compounds. Objective: In this work, we have studied the photocatalytic performance of the coupled g-C3N4/TiO2 system in the degradation of the pharmaceuticals tetracycline, ciprofloxacin, and ibuprofen. Moreover, the effect of the graphitic carbon nitride (g-C3N4) was examined through the study of two different samples, a bulk g-C3N4 prepared from the direct calcination of melamine and a mesoporous g-C3N4 synthesized through a nanocasting process using SBA-15 silica as hard template. Methods: The hybrid photocatalysts were prepared by forced hydrolysis of titanium isopropoxide using two g-C3N4 samples, a bulk material and a mesoporous one. The samples were characterized by X-ray powder diffraction (XRD), Diffuse Reflectance Spectroscopy (DRS), Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and N2 adsorption-desorption measurements. The photocatalytic activity was examined through the degradation of tetracycline, ciprofloxacin, and ibuprofen under simulated solar irradiation. Results: The textural properties of g-C3N4 play a preponderant role in the photoactivity of the g- C3N4/TiO2 system. In this sense, high dispersion of the TiO2 nanoparticles could be obtained using a mesoporous g-C3N4 sample. All hybrid photocatalysts exhibit higher degradation rates than the pristine materials, including bare TiO2. In this regard, the samples with 1 wt.% g-C3N4 attained the highest photocatalytic performance in the degradation of tetracycline, ciprofloxacin, and ibuprofen. Conclusion: The coupling of TiO2 with graphitic carbon nitride leads to the formation of hybrid photocatalysts with outstanding photoactive properties in the degradation of pharmaceutical pollutants. In this way, the g-C3N4/TiO2 samples can be considered as excellent photocatalysts for the degradation of organic pollutants.

Synergistically homogeneous-heterogeneous Fenton catalysis of trace copper ion and g-C3N4 for degradation of organic pollutants.

Using the bulk g-C3N4 as a precursor, four g-C3N4 nanosheets were further prepared by ultrasonic, thermal, acid, and alkali exfoliation. The structures of these materials were characterized by various techniques such as X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The synergistical Fenton catalysis of these materials with Cu2+ was evaluated by using rhodamine B as a simulated organic pollutant. The results showed that there existed a significant synergistical Fenton catalysis between Cu2+ and g-C3N4. This synergistic effect can be observed even when the concentration of Cu2+ was as low as 0.064 mg L-1. The properties of g-C3N4 strongly influenced the catalytic activity of the Cu2+/g-C3N4 system. The coexistent of Cu2+ and the alkali exfoliated g-C3N4 showed the best catalytic activity. Hydroxyl radicals as oxidizing species were confirmed in the Cu2+/g-C3N4 system by electron paramagnetic resonance spectra. The synergistic catalysis may be attributed to the easier reduction of Cu2+ adsorbed on the g-C3N4. This study provided an excellent Fenton catalytic system, and partly solved the rapid deactivation of heterogeneous Fenton catalysts caused by the leaching of metal ions.

Understanding the influence of single metal (Li, Mg, Al, Fe, Ag) doping on the electronic and optical properties of g-C3N4: a theoretical study

ABSTRACT Semi-empirical tight-binding-based quantum chemistry method (GFN2-xTB) has been done to study the influence of single metal (Li, Mg, Al, Fe, Ag) doping on the electronic and optical properties of monolayer corrugated graphitic carbon nitride (g-C3N4). Based on the calculated formation energy and population analysis, we showed that the metal atom is chemically bound to the g-C3N4 surface. The metal doping reduces the vertical ionisation potential and raises the electron affinity and Lewis acidity of g-C3N4. The metal-doped g-C3N4 systems have lower band gap than that of pristine g-C3N4 which is attributed to the electron donating from the metal atom to g-C3N4. Analysis of the lowest unoccupied molecular orbital and the highest occupied molecular orbital shows that for the Fe- and Ag-doped g-C3N4 systems the separation of photo-generated electron–hole pairs is efficient, resulting in the enhancement of photo-catalytic activity.

A scalable approach for functionalization of TiO2 nanotube arrays with g-C3N4 for enhanced photo-electrochemical performance

Graphitic carbon nitride (g-C3N4) has manifested itself as an effective counterpart of titanium di-oxide (TiO2) to extend its photoactivity in the visible range. In this work, g-C3N4 functionalized TiO2 nanotubes were synthesized by electrodeposition of g-C3N4 in bulk on TiO2 nanotubes from a continuously rotating organic suspension at a moderate voltage (∼90 V). Additionally, samples with varying time durations were also synthesized to examine the effect of electrodeposition time on the performance of g-C3N4 functionalized TiO2 nanotubes. Photo-electrochemical measurements demonstrated strong light induced activity, with a photocurrent density of 0.14 mA/cm2 at 1 V vs Ag/AgCl in 1 M Na2SO4 electrolyte. Maximum photoresponse for g-C3N4 functionalized TiO2 nanotubes was upto 4 factors higher than bare TiO2 nanotubes. The crystallinity, morphology and chemical compositions were investigated by XRD, FESEM and XPS respectively. Further, the optical absorption edge, chemical bonds and defects states were evaluated by UV–visible, Raman, FTIR, PL and EPR spectroscopy. The properties of g-C3N4/TiO2 system were correlated with the photocurrent behaviour and a mechanism of the probable role of vacancies and defects in their photo induced activity has been proposed. The study has established a simple and scalable scheme for the functionalization of TiO2 nanotube with g-C3N4 to achieve enhanced photo-electrochemical properties.

Facile fabrication of ZnPc sensitized g-C3N4 through ball milling method toward an enhanced photocatalytic property

ABSTRACT Ball milling (BM) is utilized to fabricate a composite photocatalyst composed of g-C3N4 material and ZnPc, which traditionally has been a sensitizer in TiO2 based solar cells yet usually having severe agglomeration problem. X-ray diffraction and FTIR results demonstrate that ZnPc has been immobilized onto g-C3N4 surfaces and that the inter-molecular bonds were also destroyed to a large extent, leading to improved dispersion of ZnPc. Further diffuse reflectance and photoluminescence characterization indicated distinct extended spectral response region at 600–700 nm as well as prohibited carrier recombination of the g-C3N4/ZnPc composite. When utilized as a photocatalyst, the properties of g-C3N4/ZnPc composites in the degradation of RhB were 3.1, 1.8 and 4.3 times higher than those of the pristine, ball-milled pure g-C3N4 and g-C3N4&ZnPc. By adding some scavengers, the main active species involved in the photocatalytic process were identified as •O2 −. The improved photocatalytic performance could be ascribed to well-matched band gaps between ZnPc and g-C3N4, extended light-responsive range as well as the better ZnPc dispersion upon g-C3N4 surfaces.

First Eurasian conference on nanotechnology, Baku, Azerbaijan photoelectrochemically-assisted bioanode constructed by Ru-complex and g-C3N4 coated MWCNT electrode

Abstract In this study, a novel photobioanode was constructed using a Ruthenium complex (Ru-complex) sensitized graphitic carbon nitride (g-C3N4) nanomaterial deposited on multi-walled carbon nanotubes (MWCNT). g-C3N4 coated MWCNT bearing Ru-complex acts as a platform for the immobilization of flavin adenine dinucleotide dependent glucose dehydrogenase (FADGDH). The formed photosensitive bioanode showed an enhancement in glucose oxidation current under visible light irradiation. The electrocatalytic current increase for in glucose oxidation are possibly due to the good electrical contacting of the immobilized FADGDH on the electrode surface and utilization of light energy. The spectroscopic properties of g-C3N4 and Ru-complex in dimethylformamide (DMF) were determined by UV–visible absorption spectra demonstrating the characteristic absorption peaks in the visible light region. Upon visible light illumination, the enzymatic photoanode revealed a prompt rise in photocurrent (ca. 1.44 μA cm−2) compared to the photoelectrode whithout enzyme (0.65 µA cm−2). Light irradiation of the bioanode improved the overall performance of the electrode as glucose oxidation was reinforced by photoelectrochemical (PEC) process.

Construction of novel 2D/1D g-C3N4/CaTiO3 heterojunction with face-to-face contact for boosting photodegradation of triphenylmethane dyes under simulated sunlight

Abstract Novel binary coupled 2D/1D g-C3N4/CaTiO3 composite photocatalysts with face-to-face contact were synthesized by a solvothermal and calcination method. The properties of g-C3N4/CaTiO3 composites were characterized by XRD, SEM, TEM, BET, UV–vis/DRS, etc. The beneficial band position tuning via coupling g-C3N4 with CaTiO3, and its 2D/1D face-to-face contacted pattern transfer electrons rapidly and retard photogenerated electrons-holes recombination. The photocatalytic ability was evaluated by using crystal violet (CV) and malachite green (MG). The as-prepared g-C3N4/2CTO sample shows the highest photocatalytic activity, and the degradation rate of CV and MG can reach up to 99.76% and 95.02% under simulate sunlight owing to the impressive synergic effect between 2D/1D g-C3N4/CaTiO3 face-to-face contact pattern. The free radical scavenging experiments demonstrate that the · O 2 − and h+ are the main active species. Further, the degradation intermediates of CV and MG detected by GC–MS found both containing phenol, 2,2-Methylenebis(6-Tert-Butyl-4-Methylphenol) (MTBM). Hence, they may have a similar degradation pathway, which provided a significant guideline for the degradation of triphenylmethane dyes. Our prepared novel 2D/1D face-to-face contact pattern nanocomposite is expected to be a fresh scheme for high-efficiency refractory pollutants degradation under sunlight.

Sunlight Photodeposition of Gold nanoparticles onto Graphitic Carbon Nitride (g-C3N4) and Application Towards the Degradation of Bisphenol A

Gold (Au) nanoparticles (NPs) were successfully deposited onto the surface of graphitic carbon nitride (g-C3N4) by using natural sunlight. Bisphenol A (BPA) were adopted as a pollutant with different pH condition to indicate the photocatalytic performance under natural sunlight. The presence of Au NPs (8.8 nm) was confirmed by TEM and XPS characterization. The duration for degraded BPA in pH 3 was 30 minutes faster than the normal degradation rate which is pH 7. This is due to the point of zero charge (PZC) properties of g-C3N4, contributing to better adsorption capacity efficiency and promoted the contact between photocatalysts and pollutants. The pH condition of BPA will affect the degradation efficiency, hence lower down pH condition of BPA can increase the photocatalytic performance.

The Synthesis, Characterization and Visible-Light Photodegradation Performance of Graphitic Carbon Nitride Coupling with CoAPO-5

In order to enhance hole/electron separation and charge transfer in photocatalysts, the heterostructured g-C3N4/CoAPO-5 hybrids materials were synthesized via a simple grinding method and were investigated using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The optical properties of g-C3N4/CoAPO-5 hybrids materials were measured by ultraviolet-visible diffuse-reflectance spectroscopy (DRS), photoluminescence (PL) spectra and ultraviolet-visible absorption (UV-Vis) spectra. Under visible-light illumination, this work shows the heterogeneous g-C3N4/CoAPO-5 hybrids present a superior photocatalytic activity.

Preparation and Visible Light Photocatalytic Property of g-C3N4/MoS2 Nanosheets/GO Ternary Composite Photocatalyst

Preparation and Visible Light Photocatalytic Property of g-C₃N₄/MoS₂ Nanosheets/GO Ternary Composite Photocatalyst

Preparation and Photocatalytic Behavior of Carbon-Nanodots/Graphitic Carbon Nitride Composite Photocatalyst

A facile one-step hydrothermal process is presented for fabrication of graphitic carbon nitride/carbon nanodots (g-C3N4/C-dots) composite photocatalyst. XRD, SEM, TEM, UV–Vis DRS and PL were adopted to analyze the effect of C-dots modification on the structure and properties of g-C3N4. Photocatalytic activity of g-C3N4/C-dots was evaluated by the degradation of methyl orange (MO) under different conditions. The results show that C-dots can increase photocatalytic reaction rate of g-C3N4/C-dots composite under visible-light irradiation, especially in the presence of H2O2. C-dots act as electron-sinks, therefore preventing the recombination of photo-generated electron-hole pairs. Meanwhile, H2O2 not only acts as an oxygen-donor to make contribution to generation of O2, but can directly react with the photo-generated electrons transferred from the conduction band of g-C3N4 to C-dots, leading to the formation of ·OH active group, which promotes the degradation of MO. Therefore the photocatalytic activities of g-C3N4/C-dots can be improved significantly when adding H2O2 to the photocatalytic reaction system.