g-C3N4 Composites Research Articles

Preparation of g-C3N4/vermiculite composite with improved visible light photocatalytic activity

Composites of g-C3N4 and vermiculite (gCNV–X, X = 10, 8, 6, 4, 2) with expanded vermiculite (VE) contents of 15.4%, 18.5%, 23.2%, 31.2%, and 47.6% were synthesized by a wet chemical method and provided confined space due to VE. Nanosheets or nanoparticles of g-C3N4 were homogeneously distributed in the gCNV–X composites. With increasing VE content, the photocatalytic activity of gCNV–X improved first, reached the optimum at a VE content of 18.5% (gCNV-8), and then decreased gradually. Composite gCNV-2, with a high VE content of 47.6%, exhibited a similar photocatalytic performance as pure g-C3N4 (gCN). After photocatalysis for 70 min, composite gCNV-8 had degraded 98.07% of RhB with a reaction rate constant that was approximately three times larger than that of gCN. Furthermore, gCNV-8 showed excellent stability and reusability. The composite g-C3N4/vermiculite exhibited an excellent photocatalytic performance, which was ascribed to the reduced particle size of g-C3N4, close interfacial contact, electrostatic interactions between g-C3N4 and vermiculite, enhanced photocarrier separation efficiency, improved photocurrent and light absorption ability, as well as a narrow band gap.

Study on surface sensitization of g-C3N4 by functioned different aggregation behavior porphyrin and its optical properties

Tetracarboxyl-phenyl porphyrin (TCPP) hybridized graphitic carbon nitride (g-C3N4) composites have been facilely synthesized through grinding method and ethanol dispersion. TCPP molecules as a sensitizer could easily assemble on the surface of g-C3N4 nanosheets mainly through π–π stacking interaction. The TCPP-g-C3N4 composite is employed to optical waveguide (OWG) gas sensor, and its aggregation behaviors in different pH condition are studied by UV–vis spectroscopy and the corresponding morphologies are observed by SEM. It is found that the TCPP-g-C3N4 film under basic condition (pH = 11), where TCPP formed H - type aggregation on the film surface, has fine response to SO2 (0.1–100 ppm) and H2S (1–100 ppm). The gas-sensitive mechanism is protonation and deprotonation process, in terms of UV–vis spectroscopy.

G-C3N4 nanoparticle@porous g-C3N4 composite photocatalytic materials with significantly enhanced photo-generated carrier separation efficiency

Abstract

Fabrication of novel tetrahedral Ag3PO4/g-C3N4/BiVO4 ternary composite for efficient detoxification of sulfamethoxazole

Wide spread of antibiotic resistant microorganisms and genes urge the evolution of effective methods to remove antibiotic pollution from the environment. Ag3PO4 is one of the best visible light photocatalyst but has drawbacks due to low stability. Combining Ag3PO4 with BiVO4 and g-C3N4 is expected to overcome these drawbacks and improve the efficiency. The present study deals with preparation of tetrahedral Ag3PO4/g-C3N4/BiVO4 ternary composite with superior photocatalytic activity and stability for efficient detoxification of sulfamethoxazole (SMX). Pure BiVO4 (51.3 %), g-C3N4 (40.2 %), Ag3PO4 (60.1 %) and other composites showed lower efficiency than Ag3PO4/g-C3N4/BiVO4 (93.6 %) in photodegradation of SMX (20 mg/L) after 60 min. Tetrahedral Ag3PO4 showed superior light adsorption capacity and photocatalytic activity when combined with g-C3N4/BiVO4 and also showed reduced charge recombination which were supported by UV-DRS and PL analysis. The synergistic effects of both g-C3N4 and Ag3PO4/BiVO4 in the structure could facilitate the enhanced photostability and recyclability to Ag3PO4. Furthermore, the intermediate compounds generated during degradation of SMX were analyzed by LC-MS analysis and the plausible pathway was proposed. Moreover, the biotoxicity of the intermediate compounds was investigated by Escherichia coli (E. coli) colony forming unit assay and the results revealed that after 60 min a substantial decrease in biotoxicity was observed.

Ag2CO3-derived Ag/g-C3N4 composite with enhanced visible-light photocatalytic activity for hydrogen production from water splitting

In this paper, Ag-based g-C3N4 composites have been successfully fabricated through two deferent synthetic methods: (i) a facile and efficient precipitation-calcination strategy (denoted as D–CN–xAg, x represents the dosage of Ag2CO3, the same below), (ii) a calcination method (denoted as Z–CN–xAg). All Ag-based g-C3N4 composites exhibit the enhanced photocatalytic activities under visible-light irradiation. Moreover, the optimal dosage of Ag2CO3 in the D–CN–xAg composite is found to be 5%, the corresponding hydrogen production capacity is 153.33 μmol g−1 h−1, which is 4.6 times higher than that of Z–CN–5%Ag composite. This might be attributed to appropriate content of metallic Ag and more active sites exposed on the surface of D–CN–5%Ag composite. Meanwhile, combining with photoelectrochemical results, it could be inferred that LSPR effect and the intimate interfacial between metallic Ag and g-C3N4 in the system play also important role for the improvement of photocatalytic activity. These results demonstrate that the appropriate loading of metallic Ag originated from Ag2CO3 into g-C3N4 could accelerate the separation and transfer of photogenerated electron-hole pairs, leading to the improvement of photocatalytic activity for hydrogen production from water splitting. Finally, a possible photocatalytic mechanism is proposed.

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.

Construction of 2D/2D Z-scheme MnO2-x/g-C3N4 photocatalyst for efficient nitrogen fixation to ammonia

Reducing nitrogen to ammonia with solar energy has become a wide concern when it comes to photocatalysis research. It is considered to be one of the more promising alternate options for the conventional Haber–Bosch cycle. Herein, 2D g-C3N4 composites with modifying ultrathin sheet MnO2-x were prepared and used as nitrogen fixation photocatalyst. With the assistance of the nature of MnO2-x, the generation rate of NH3 reached 225 μmol g−1 h−1, which is more than twice over the rate of pristine 2D g-C3N4 (107 μmol g−1 h−1). The presence of ultrathin sheet MnO2-x shortens the gap of the carriers to the surface of photocatalyst. Thus the speed of electron transfer gets increased. Besides, the construction of Z-scheme heterojunction boosts the separation and migration of photogenerated carriers. As a result, the nitrogen reduction reaction (NRR) performance gets enhanced. The work may provide an example of promoting the NRR performance of non-metallic compound.

Enhanced photocatalytic nitrogen fixation of Ag/B-doped g-C3N4 nanosheets by one-step in-situ decomposition-thermal polymerization method

Photocatalytic nitrogen fixation is considered as a promising strategy for ammonia production. In this study, non-metallic boron and noble metal silver modified graphitic carbon nitride were prepared by a direct in-situ decomposition-thermal polymerization method with dicyandiamide, boric acid and silver nitrate as the precursors. It was shown that Ag/B-doped g-C3N4 composites with optimal mass ratio exhibited improved photocatalytic ammonia production under simulated sunlight illumination by a factor of 5.5 and 1.5 times compared with the pristine g-C3N4 and B-doped g-C3N4, respectively. The superior photocatalytic property was attributed to the decreased band gap and formation of mesopores after boron doping, which enlarged the specific surface area and created abundant reactive sites on the g-C3N4 nanosheets. In addition, the loaded silver nanoparticles greatly inhibited the recombination of photogenerated charge carriers through heterojunction interface. This work provided new deep insights into the reasonable structure of g-C3N4 composite system for photocatalytic nitrogen fixation reactions.

Au/TiO2(P25)-gC3N4 composites with low gC3N4 content enhance TiO2 sensitization for remarkable H2 production from water under visible-light irradiation

Abstract A series of ternary Au/TiO2(P25)-gC3N4 heterostructure photocatalysts with low Au nanoparticle (NP) loading and gC3N4 content were synthesized and evaluated for H2 production from water with a very low amount of sacrificial agent (1 vol%) under solar and visible-light irradiation. The optimized composite, 0.3 wt% Au/TiO2(P25)-gC3N4 (95–5), exhibited a remarkable production rate under visible light (419 μmol−1 h−1 gcatalyst of H2), corresponding to almost twice the cumulated H2 production over 2.5 h as that of the Au/TiO2 (P25) reference. To best of our knowledge, this high of a yield has never been reported for comparable experimental conditions. The highest performing composite was characterized using UV–vis, XPS, UPS, BET, TEM, and TRMC techniques. The performance of the photocatalyst could be correlated to contributions of various phenomena such as effective heterojunction formation of TiO2 with gC3N4 operating in a Z-scheme dynamic allowing TiO2 photosensitization towards visible-light, also leading to new electronic hybrid states, and plasmonic Au/support Schottky junction allowing electronic trapping sites and co-catalytic effects. These contributions resulted in more efficient light harvesting and separation of the charge carriers to enhance visible light driven activity.

The metallic 1T-phase WS2 nanosheets as cocatalysts for enhancing the photocatalytic hydrogen evolution of g-C3N4 nanotubes

Herein, we report that 2D metallic 1T-WS2 acts as co-catalyst in assisting g-C3N4 nanotubes (NTs) obtained via a simple grinding method for promoting photocatalytic H2 production. The 1T-WS2/g-C3N4 composite with optimum 27% 1T-WS2 displays a significantly improved photocatalytic H2 production rate (1021 μmol h−1 g−1), 17.6 times higher than g-C3N4 NTs. Besides, the apparent quantum efficiency (AQE) of 1T-WS2/g-C3N4 composite (27%) achieves 11.23% under light at λ = 370 nm. Meanwhile, the 1T-WS2/g-C3N4 composites present an excellent photocatalytic H2 production stability. The possible photocatalytic mechanism over 1T-WS2/g-C3N4 composites is proposed. Specifically, the photogenerated electrons from 1D g-C3N4 tubular nanostructure with open mesoporous morphology are migrated to conductive 1T-WS2 NSs quickly as electron acceptors along the 1D path. 1T-WS2 NSs can also offer abundant active sites on the edge and basal planes.

Graphitic carbon nitride-doped sewage sludge as a novel material for photodegradation of Eriochrome Black T.

The bio-resource utilization of sewage sludge is presented by preparation of novel waste sludge-doped graphite carbon nitride (g-C3N4) photocatalyst. The sludge flocs which constitute bacteria and organic substances served as a pore-forming framework in the catalyst, while the inorganic fractions including those transition metals and crustal metals can function as dopants for sludge-based g-C3N4 composite. The physicochemical properties of as-prepared catalyst were well analyzed by multiple characterizations. The composite catalyst showed higher surface area (50m2/g) and more mesoporous structures (8.9 × 10-2cm3/g) as compared with pristine g-C3N4 (8.4m2/g and 6.6 × 10-2cm3/g, respectively). The photoelectrochemical results showed that introduced sewage sludge impurities lowered down the photocarriers recombination efficiency and enhanced more efficient electron-hole separation by about 100 times. The photocatalytic activity was tested by degradation of typical dye Eriochrome Black T (EBT). The optimal sample improved removal of EBT by 56% in 90min under ultraviolet irradiation (λ = 254nm). According to the results of main metal ion leaching concentration and reuse tests, the composite catalyst exhibited excellent stability and repeatability.

Water hyacinth derived carbon quantum dots and g-C3N4 composites for sunlight driven photodegradation of 2,4-dichlorophenol

Carbon dots (CDs) were successfully derived from water hyacinth leaves and the binary composite was achieved by incorporating CDs with g-C3N4 through hydrothermal treatment. The average particle size of CDs was found to be 3.1 nm and a blue-green fluorescence was emitted under the UV light irradiation. Both of the composites loaded with 20 wt.% (20CDs/g-C3N4) and 40 wt.% (40CDs/g-C3N4) of CDs achieved the highest degradation efficiency of 2,4-dichlorophenol (2,4-DCP) with 1.7 times higher than that of pure g-C3N4. This work successfully improved the properties of g-C3N4 by elongating the lifetime of photogenerated electrons and widening the visible light response. Both of 20CDs/g-C3N4 and 40CDs/g-C3N4 recorded the highest photocatalytic performance in degrading 2,4-DCP with degradation rate constant of 0.0194, and 0.0186 min−1, respectively. This is contributed by the prolonged charge carrier lifetime in 20CDs/g-C3N4; good visible light absorption and high specific surface area in 40CDs/g-C3N4. For the scavenger test, hole (h+) and superoxide radical (·O2−) were acknowledged as the key active species in photocatalysis.

Rationalizing and controlling the phase transformation of semi-metallic 1T′-phase and semi-conductive 2H-phase MoS2 as cocatalysts for photocatalytic hydrogen evolution

In this study, we report that the 2D semi-metallic 1T′-MoS2 serves as co-catalyst in assisting 1T′-MoS2/g-C3N4 composites obtained via a one-pot hydrothermal technique for boosting photocatalytic H2 evolution, and the phase transformation from 1T′ to 2H is achieved via thermal treatment. The designed 1T′-MoS2/g-C3N4 composite exhibits significant enhancement than pure g-C3N4 and 2H-MoS2/g-C3N4. The 1T′-MoS2/g-C3N4 composite with optimum 20 wt% 1T′-MoS2 displays a significantly improved photocatalytic H2 production rate (4426 μmol·h−1·g−1), which is about 86.7 and 1.41 times of pure g-C3N4 and 20 wt%–2H-MoS2/g-C3N4 composite, along with excellent stability. Besides, the apparent quantum efficiency (AQE) of 1T′-MoS2/g-C3N4 composite (20 wt%) achieves 13.55%. 1T′-MoS2 co-catalysts not only serve as effective electron acceptors, but have the merits of the energetically more stable.

Visible-light-driven nitrogen-doped carbon quantum dots decorated g-C3N4/Bi2WO6 Z-scheme composite with enhanced photocatalytic activity and mechanism insight

Abstract In this work, the g-C3N4/Bi2WO6 Z-scheme composites were synthesized by in-situ calcination and hydrothermal method and the novel g-C3N4/Bi2WO6/NCQs was constructed by introducing nitrogen-doped carbon quantum dots (NCQs) on the interface of g-C3N4/Bi2WO6 catalyst. UV–vis spectroscopy data showed that the improved visible light utilization efficiency of the catalyst is attributed to the composition of g-C3N4/Bi2WO6 Z-scheme heterojunction and the addition of NCQs. Photocurrent response analysis and fluorescence intensity measurements showed that the high separation efficiency of photogenerated electron-hole pairs in the g-C3N4/Bi2WO6/NCQs composite. In addition, the excellent structural stability of g-C3N4/Bi2WO6/NCQs can be proved by the analysis data of cycle experiments and XRD diffraction peaks of catalysts before and after experiments. Obviously, the above experimental data and analysis demonstrated the outstanding photocatalytic activity of g-C3N4/Bi2WO6/NCQs. Free radical capture experimental data analysis confirmed that superoxide ion radicals (·O2−) and holes (h+) play a major role in the reaction process, and the possible photocatalytic mechanism of g-C3N4/Bi2WO6/NCQs was proposed to further understand its enhanced photocatalytic activity.

Novel synthesis of Z-scheme α-Bi2O3/g-C3N4 composite photocatalyst and its enhanced visible light photocatalytic performance: Influence of calcination temperature

In this study, α-Bi2O3/g-C3N4 nanocomposite with direct Z-scheme was successfully prepared through calcination of BiOCOOH/g-C3N4 precursor at different temperature. Meanwhile, the effect of calcination temperature on the physicochemical properties of α-Bi2O3/g-C3N4 was studied. All results confirmed that calcination temperature greatly influences structural, morphology, surface states, photoelectrochemical property and photocatalytic (PC) performance of α-Bi2O3/g-C3N4 composite. Furthermore, the α-Bi2O3/g-C3N4 composite was applied as photocatalyst to degrade amido black 10B dye under visible light irradiation. It was found that the composite synthesized at 400 °C exhibited the highest PC performance due to the intense visible light absorbance and high separation efficiency of electron and hole pairs. Besides, the possible PC mechanism was proposed that the photo-generated charge carrier migration in α-Bi2O3/g-C3N4 photocatalyst followed a Z-scheme structure. Finally, the stability test also manifest that the α-Bi2O3/g-C3N4 composite photocatalyst has good stability and reusability, which was a promising candidate for wastewater treatment.

Noble Metal-Free TiO2-Coated Carbon Nitride Layers for Enhanced Visible Light-Driven Photocatalysis.

Composites of g-C3N4/TiO2 were one-step prepared using electron impact with dielectric barrier discharge (DBD) plasma as the electron source. Due to the low operation temperature, TiO2 by the plasma method shows higher specific surface area and smaller particle size than that prepared via conventional calcination. Most interestingly, electron impact produces more oxygen vacancy on TiO2, which facilitates the recombination and formation of heterostructure of g-C3N4/TiO2. The composites have higher light absorption capacity and lower charge recombination efficiency. g-C3N4/TiO2 by plasma can produce hydrogen at a rate of 219.9 μmol·g−1·h−1 and completely degrade Rhodamine B (20mg·L−1) in two hours. Its hydrogen production rates were 3 and 1.5 times higher than that by calcination and pure g-C3N4, respectively. Electron impact, ozone and oxygen radical also play key roles in plasma preparation. Plasma has unique advantages in metal oxides defect engineering and the preparation of heterostructured composites with prospective applications as photocatalysts for pollutant degradation and water splitting.

1 T-phase molybdenum sulfide nanodots enable efficient electrocatalytic nitrogen fixation under ambient conditions

Herein, 1T-phase MoS2 nanodots (NDs) anchored to g-C3N4 (1T-MoS2/g-C3N4) are firstly developed to operate as a highly efficient catalyst for electrochemical N2 fixation with superior selectivity. 1T-MoS2/g-C3N4 composite presents outstanding NRR performance with a FE of 20.48 % and a NH3 yield rate of 29.97 μg h−1 mg−1cat. at -0.3 V vs. RHE. Furthermore, 1T-MoS2/g-C3N4 composite also shows outstanding electrochemical stability and durability. 15N isotopic labeling experiment confirms that nitrogen in produced ammonia originates from N2 in electrolyte rather than the decomposition of g-C3N4. DFT calculations reveal the optimal reaction path of NRR with both associative distal and alternating pathways. This work may offer a hopeful lead for designing effective non-noble-metal NRR electrocatalysts.

Efficient Selective Sorption of Cationic Organic Pollutant from Water and Its Photocatalytic Degradation by AlVO₄/g-C₃N₄ Nanocomposite.

This study reports the synthesis, characterization and water remediation application of novel AlVO₄/g-C₃N₄ nanocomposites. The nanocomposite has been synthesized by a low temperature solid-state reaction using graphitic carbon nitride (g-C₃N₄) obtained via calcination of melamine and AlVO₄ prepared via assisted sonochemical technique. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier Transform Infrared spectroscopy (FTIR), ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS), and the N₂ gas adsorption Brunauer-Emmett-Teller (BET) method has been used to characterize the pristine and composite samples. AlVO₄ and g-C₃N₄ interact with each other forming a hybrid composite, which shows excellent ability for selective sorption of cationic MB (methylene blue) dye from wastewater. The initial dye concentration, pH and amount of sorbent has been varied and their effect on the adsorption process has been analysed. The photocatalytic efficiency of the MB dye adsorbed pristine g-C₃N₄, AlVO₄:g-C₃N₄ (1:3) and AlVO₄:g-C₃N₄ (1:1) composite has been tested under visible light. With increased proportion of AlVO₄ in the samples, the photocatalytic efficiency improved and the best photodegradation has been observed for the AlVO₄:g-C₃N₄ (1:1) sample. Photoluminescence (PL) studies, photocurrent response measurements and electrochemical impedance spectroscopy (EIS) indicates enhanced separation of the photogenerated electron/hole pairs leading to effective degradation of the MB dye solution in case of the AlVO₄:g-C₃N₄ (1:1) composite sample. The photocatalytic mechanism has been elucidated and it could be inferred that photogenerated holes and superoxide anion radicals play a major role in the photocatalysis process.

Z-scheme Fe2O3/g-C3N4 heterojunction with excellent photocatalytic property

To develop a photo-Fenton catalyst that works under mild conditions, we report the fabrication of Fe2O3 / g-C3N4 composite via a simple two-step calcination process for the degradation of phenol under room temperature, neutral solution, and simulated sunlight. The photo-Fenton catalytic degradation constant of the Fe2O3 / g-C3N4 composite is 7.07 and 7.62 times that of Fe2O3 and g-C3N4, respectively. The limited size of Fe2O3 and partial reduction of Fe3 + in the Fe2O3 / g-C3N4 composite promotes the production of · OH radical. The Z-mechanism with efficient charge separation efficiency contributes to the enhanced photo-Fenton catalytic performance.

Photocatalytic oxidative desulfurization and denitrogenation for fuels in ambient air over Ti3C2/g-C3N4 composites under visible light irradiation

MXene Ti3C2 modified g-C3N4 composites were prepared and used in photocatalytic oxidative denitrogenation and desulfurization under visible light. The photocatalysis system adapted to oxidation of small molecular pyridine and thiophene for fuels in the ambient air without adding extra H2O2 or pure O2 oxidants. Structural and photoelectric properties of the photocatalysts were characterized and compared. In an optimal composite, g-C3N4 nanosheets were successfully intercalated by Ti3C2 layers to form an interfacial effect and heterojunction. Intercalation effect accelerated the photogenerated electrons transferring from g-C3N4 to Ti3C2, and inhibited the recombination of electron-hole pairs. Ti3C2/g-C3N4 composite exhibited enhanced photocatalytic performance, high mineralization efficiency, and good recyclability in the removal of pyridine and thiophene. Mechanism and DFT studies proposed that the holes acted as the major active species for the photocatalysis procedures to form the reactant intermediates, while the electrons and O2 generated superoxide radicals provided a promotion effect on the final conversions.