3N4 Nanosheets Research Articles

Ionic liquid-assisted synthesis of porous boron-doped graphitic carbon nitride for photocatalytic hydrogen production

This work presents a simple way to prepare boron-doped graphitic carbon nitride (B/g-C3N4), exhibiting an enhanced photocatalytic performance to split water for hydrogen production. B/g-C3N4 was synthesized via the pyrolysis of urea and 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim]BF4), which was adopted as the boron source. The aggregate of B/g-C3N4 nanosheets shows a porous structure since some bubbles are generated under the heat decomposition of ionic liquids. The porous structure is conducive to the exposure of more active sites. Moreover, B-doping will form some localized electronic energy levels in the band gap of g-C3N4, thereby extending its visible light response. As impacted by the porous structure of B/g-C3N4 aggregate and the narrow the band gap, the photocatalytic hydrogen generation rate (901 μmol h−1 g−1) is increased, almost 3 times faster than g-C3N4 (309 μmol h−1 g−1). This work proposed a simple method to prepare the aggregate of B/g-C3N4 nanosheets exhibiting pores under ionic liquid assistance. It can be a novel method to design porous polymer photocatalysts.

2D PtS nanorectangles/g-C3N4 nanosheets with a metal sulfide-support interaction effect for high-efficiency photocatalytic H2 evolution.

Cocatalyst design is a key approach to acquire high solar-energy conversion efficiency for photocatalytic hydrogen evolution. Here a new in situ vapor-phase (ISVP) growth method is developed to construct the cocatalyst of 2D PtS nanorectangles (a length of ∼7 nm, a width of ∼5 nm) on the surface of g-C3N4 nanosheets. The 2D PtS nanorectangles/g-C3N4 nanosheets (PtS/CN) show an unusual metal sulfide-support interaction (MSSI), which is evidenced by atomic resolution HAADF-STEM, synchrotron-based GIXRD, XPS and DFT calculations. The effect of MSSI contributes to the optimization of geometrical structure and energy-band structure, acceleration of charge transfer, and reduction of hydrogen adsorption free energy of PtS/CN, thus yielding excellent stability and an ultrahigh photocatalytic H2 evolution rate of 1072.6 μmol h-1 (an apparent quantum efficiency of 45.7% at 420 nm), up to 13.3 and 1532.3 times by contrast with that of Pt nanoparticles/g-C3N4 nanosheets and g-C3N4 nanosheets, respectively. This work will provide a new platform for designing high-efficiency photocatalysts for sunlight-driven hydrogen generation.

Engineering Z-system hybrids of 0D/2D F-TiO2 quantum dots/g-C3N4 heterostructures through chemical bonds with enhanced visible-light photocatalytic performance

A Z-system hybrid of F-TiO2 quantum dots/g-C3N4 nanosheets with an effective pathway (C–O bond) for charge transfer and selective recombination was constructed.

Electrochemical hydrogen evolution reaction efficiently catalyzed by Ru–N coupling in defect-rich Ru/g-C3N4 nanosheets

Defect-rich Ru/g-C3N4 nanosheets with efficient Ru–N coupling are reported for hydrogen generation both in alkaline and acidic electrolytes.

Doping and heterojunction construction dual-regulation: Magnetically recoverable CoFe1.9Y0.1O4/g-C3N4 nanosheets with enhanced visible-light-driven photocatalytic activity

The development of efficient recoverable photocatalysts for organic pollution photodegradation has been one of the hot subjects in the past decades as a result of environmental concerns. Herein, a magnetically separable photocatalyst was successfully prepared by coupling Y-doped CoFe2O4 and graphitic carbon nitride through a simple calcination process. The obtained CoFe1.9Y0.1O4/g-C3N4 composite photocatalyst exhibited a saturation magnetization of 9.96 emu·g−1 at 300 K, indicating superior magnetic characteristic. Remarkably, the optimal photocatalytic activity of the CoFe1.9Y0.1O4/g-C3N4 for methylene orange (MO) degradation under visible light irradiation was increased up to about 3.4, 2.3 and 2.0 times larger than that of pure CoFe2O4, g-C3N4 and CoFe1.9Y0.1O4, respectively. Further studies indicated the improved performance could be attributed to the Y doping as well as the type II heterojunction formed between CoFe1.9Y0.1O4 and g-C3N4.

A novel Au/g-C3N4 nanosheets/CeO2 hollow nanospheres plasmonic heterojunction photocatalysts for the photocatalytic reduction of hexavalent chromium and oxidation of oxytetracycline hydrochloride

Au/g-C3N4/CeO2 plasmonic heterojunction has been successfully fabricated, which was constructed by forming the three-dimensional hollow CeO2 mesoporous nanospheres on the two-dimensional Au/g-C3N4 nanosheets. The photocatalysts not only exhibited excellent catalytic reduction activity against Cr6+, but also oxidized oxytetracycline hydrochloride (OTH), and OTH catalytic degradation route was suggested by the degradation products determined by GC–MS. The improvement of photocatalytic performance comes from the high absorption capability of visible light and effective interface charge separation. Finally, it speculated that the Au/g-C3N4/CeO2 heterostructures followed Z-scheme charge transfer mechanism in this study, which is verified by the analysis of experiment and theoretical calculation results.

Z-scheme Au decorated carbon nitride/cobalt tetroxide plasmonic heterojunction photocatalyst for catalytic reduction of hexavalent chromium and oxidation of Bisphenol A

Au/g-C3N4/Co3O4 plasmonic heterojunction photocatalyst was successfully prepared by in-situ forming Co3O4 nanocubes on the Au/g-C3N4 nanosheets. The catalytic activities of the photocatalysts were systematically studied through the catalytic reduction of hexavalent chromium (Cr6+) and oxidation of Bisphenol A (BPA) under visible light irradiation, while according to the degradation products determined by GC-MS, the catalytic degradation pathway of BPA was proposed. 4Au/g-C3N4/Co3O4 sample exhibits the most efficient catalytic activities, and the photocatalytic reduction and photocatalytic oxidation efficiencies can obtain 85.6% and 90.3%, respectively. The main reasons of the enhancing catalytic performance are the high absorption capability to visible light generated by localized surface plasmon resonance and the effective interface charge separation. Finally, we speculated that the Au/g-C3N4/Co3O4 sample followed Z-scheme charge transfer mechanism in this study, which is verified by the analysis of experiment and theoretical calculation results.

Z-Scheme LaCoO3/g-C3N4 for Efficient Full-Spectrum Light-Simulated Solar Photocatalytic Hydrogen Generation.

Photocatalytic decomposition of water is the most attractive method for the sustainable production of hydrogen, but the development of a highly active and low-cost catalyst remains a major challenge. Here, we report the preparation of LaCoO3/g-C3N4 nanosheets and the utilization of LaCoO3 instead of noble metals to improve the photocatalytic activity for the production of hydrogen. First, LaCoO3 was successfully prepared by the sol–gel method, and then a series of highly efficient Z-scheme LaCoO3/g-C3N4 heterojunction photocatalysts were synthesized by the solvothermal method. Various characterization techniques (X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS), photoluminescence (PL), transient photocurrent response test, electron paramagnetic resonance (EPR)) confirm that the heterostructure and interfacial interaction had been formed between LaCoO3 nanoparticles and g-C3N4 nanosheets. In the photocatalytic water splitting test, LaCoO3/g-C3N4-20 wt % exhibited the highest photocatalytic activity of 1046.15 μmol h–1 g–1, which is 3.5 and 1.4 times higher than those of LaCoO3 and g-C3N4, respectively. This work leads to an inexpensive and efficient LaCoO3/g-C3N4 photocatalysis system for water splitting or other photocatalytic applications.

Furfuryl Alcohol Production with High Selectivity by a Novel Visible-Light Driven Biocatalysis Process

Enzymatically upgrading furfural (FAL), the crude platform chemical derived from biomass, to the value-added furfuryl alcohol (FOL) has attracted considerable interest because of its high conversion and selectivity. However, the conventional biotransformation of FAL to FOL was limited by the difficulties in coenzyme regeneration. Herein, visible light-driven selective hydrogenation of FAL was realized on the basis of a coupled process that consisted of a photocatalyst and alcohol dehydrogenase (ADH). The QDs/g-C₃N₄ nanosheet was prepared in a “one-pot” process using graphitic carbon nitride (g-C₃N₄) and carboxyl-modified quantum dots (QDs) (CdSe/ZnS). The as-prepared material exhibited synergetically intensified charge generation and transfer properties, implementing the regeneration of nicotinamide adenine dinucleotide (NADH). As expected, the QDs/g-C₃N₄ exhibits an equilibrium NADH yield of 95.7%, which was two times higher than that using g-C₃N₄. The reusability of the QDs/g-C₃N₄ was also acceptable. After nine batches of operation, the conversion rate of NADH was still above 70%. Adopting the nanosheet in the selective hydrogenation by the photobiocatalytic process could reach excellent FOL yield (0.6 mM) and selectivity (∼100%).

Growing ordered CuO nanorods on 2D Cu/g-C3N4 nanosheets as stable freestanding anode for outstanding lithium storage

Two dimensional (2D) nanostructures are promising to provide a new hierarchical architecture for transition metal oxides (TMOs) with outstanding lithium storage. In this work, we grew ordered CuO nanorods on 2D Cu/g-C3N4 nanosheets to form the hierarchical CuO@Cu/g-C3N4 nanorods film as freestanding anode for advanced lithium storage. This assembled freestanding film demonstrates a high discharge specific capacity at 726 mAhg−1 after 200 cycles at 0.1C and a discharge specific capacity of 457 mAhg−1 after 625 cycles at 1C, among the best performance in CuO and CuO based nanostructures for lithium storage. Its outstanding stability and cyclic performance are ascribed to the following aspects during the reaction process: (i) the unique 2D nanostructure provides large exposed area for Li+ insertion, (ii) the ordered CuO nanorods provide interior spaces to accommodate the volume change and offer more paths for charges and Li+ transfer, (iii) the existence of Cu nanosheets increases the electrons transport and (iv) the porous g-C3N4 nanosheets endow the prepared structure more active sites for facilitating Li+ transport and accommodating volume change. Our strategy on growing ordered nanostructures on 2D nanosheets will be an effective way to modify TMOs for advanced lithium-ion batteries.

Study on photocatalytic performance of hexagonal SnS2/g-C3N4 nanosheets and its application to reduce U (VI) in sunlight

In the present work, the photocatalytic technology is applied to remove hexavalent uranium(U(VI)) to purify the uranium-containing wastewater which discharged from the nuclear industry. To improve the optical performance of g-C3N4 nanosheets (g-CNNs), two-dimensional (2D) hexagonal SnS2 nanosheets were introduced, and the hererostructured catalysts show excellent removal performance for U(VI). It is worth noting that in the actual photocatalytic experiment under sunlight, the removal rate of U(VI) by 0.08-SnCN reached 90% at 2 h, indicating its high-efficiency catalytic performance and energy-saving potential. Subsequently, the introduction of organic matter simulates the actual uranium-bearing wastewater environment. Meanwhile, a series of characterization methods such as XRD, FT-IR, SEM, TEM, and UV–vis DRS were used to investigate the structure, morphology, and photoelectric properties of the photocatalysts. Furthermore, TEM, XPS, XRD and ESR were used to explore the catalytic mechanism. The results indicated that U(VI) was reduced by superoxide radical (⋅O2–) while competing electrons on the material surface, and deposited on the interface between SnS2 and g-CNNs in the form of (UO2)O2·H2O.

Preparation of Ag3PO4 Quantum Dots/g-C3N4 Nanosheet Composite Photocatalysts and Its Activity for Selective Oxidation of Benzyl Alcohol

Preparation of Ag3PO4 Quantum Dots/g-C3N4 Nanosheet Composite Photocatalysts and Its Activity for Selective Oxidation of Benzyl Alcohol

Depositing Ag2S quantum dots as electron mediators in SnS2/g-C3N4 nanosheet composites for constructing Z-scheme heterojunction with enhanced photocatalytic performance

The novel Z-scheme heterojunction photocatalyst g-C3N4/Ag2S/SnS2 with Ag2S quantum dots as electron mediators was successfully synthesized by in-situ ion exchange reaction and self-peeling of g-C3N4. Compared with g-C3N4, SnS2 or g-C3N4/SnS2, the photocatalyst g-C3N4/Ag2S/SnS2 exhibited more excellent photocatalytic performance under visible light irradiation. The removal rate of methyl orange was 96.8% after 30 minutes visible light irradiation and the reaction rate constant reached 0.10225 min-1. The enhanced photocatalytic activity could be attributed to the formation of Z-scheme heterojunction structure and the 2D layered structure. The electrochemical and photoelectric performance tests showed that the separation and transfer efficiency of the photogenic electron-hole pairs as well as the redox potential were significantly improved. Additionally, the quenching experiments showed that the superoxide radicals and holes were the primarily active species. Combined with other characterizations, the reaction mechanism of the g-C3N4/Ag2S/SnS2 for degrading the target pollutant methyl orange under visible light irradiation was proposed.

Acid-induced molecule self-assembly synthesis of Z-scheme WO3/g-C3N4 heterojunctions for robust photocatalysis against phenolic pollutants

Searching for effective strategies of boosting charge carrier separation and improving photooxidation ability are highly desirable to design graphitic carbon nitride-based photocatalysts for efficient organic pollutant degradation. Here we demonstrate an in situ acid-induced self-assembly of melamine and sodium tungstate method combined with hydrothermal treatment, by forming WO3/melamine-cyanuric acid supramolecular complex, to fabricate porous sheet-like WO3/g-C3N4 heterojunctions with oxygen doping; meanwhile, the morphology of WO3/g-C3N4 nanosheets can be further regulated by selecting different short-chain carboxylic acids. The heterojunctions exhibit enhanced visible-light photocatalytic activity than bulk g-C3N4 and supramolecule-based g-C3N4 in degradation of phenolic pollutants, acetaminophen and methylparaben. The tests including active species trapping, photoelectrochemistry and photoluminescence firmly evidence that the extraordinary Z-scheme charge transfer manner plays dominated role to this excellent activity, which can accelerate charge carrier separation and retain powerful redox ability of electrons on conduction band of g-C3N4 and holes on valence band of WO3 simultaneously; additionally, porous sheet-like nanostructures and oxygen doping also positively influence the activity via improving light harvesting, providing plentiful active sites, shortening charge carrier migration distance and further facilitating charge carrier separation. LC–MS analysis and TOC monitoring find the target pollutants are completely degraded under oxidation of holes, superoxide and hydroxyl radicals.

Selective sensing of Mn2+ based on ZnCdS/ZnS QD/carboxymethyl chitosan/g-C3N4 nanosheet nanocomposite film by the conformational regulation of polymer chain

A novel film consisting of ZnCdS/ZnS quantum dots (QDs) and g-C3N4 nanosheets conjugated with carboxymethyl chitosan (CMCS) chains via weak bonds was built. The Mn2+ in contact with the composite film forced the chitosan to undergo conformational changes, resulting in the intermolecular complex R–COO–(Mn2+)–NH2–R, which enhanced the fluorescence. The film was developed for trace Mn2+ determination according to the fluorescence resonance energy transfer mechanism by the enhancement effect of the film. The sensor exhibited a good linearity (F = 2.0852C + 168.667) for Mn2+ at a concentration of 1.961 × 10−6–1.667 × 10−5 mol/L under certain conditions with a correlation coefficient of 0.9981. The film was successfully used to determine Mn2+ with recoveries in the range of 90%–107% in the real water samples. The proposed method provides a simple, facile, sensitive, and fast detection method for Mn2+.

Mg-O-Bridged Polypyrrole/g-C3 N4 Nanocomposites as Efficient Visible-Light Catalysts for Hydrogen Evolution.

It is highly desired to improve the visible-light activity of g-C3 N4 for H2 evolution by constructing closely contacted heterojunctions with conductive polymers. Herein, a polymer nanocomposite photocatalyst with high visible-light activity is fabricated successfully by coupling nanosized polypyrrole (NPPy) particles onto g-C3 N4 nanosheets through a simple wet-chemical process, and its visible-light activity is improved further by constructing Mg-O bridges between the NPPy and g-C3 N4 . The amount-optimized bridged nanocomposite displays an approximately ninefold improvement in visible-light activity compared with g-C3 N4 . On the basis of transient-state surface photovoltage responses, photoluminescence spectra, . OH amount evaluation, and photoelectrochemical curves, it is concluded that the exceptional photoactivity can be attributed to the significantly promoted charge transfer and separation along with visible photosensitization from NPPy. Interestingly, it is confirmed that the promoted charge separation depends mainly on the excited high-level electron transfer from g-C3 N4 to NPPy by single-wavelength photocurrent action spectra. This work provides a feasible strategy for designing polymer nano-heterojunction photocatalysts with exceptional visible-light activities.

Two dimensional Co3O4/g-C3N4 Z-scheme heterojunction: Mechanism insight into enhanced peroxymonosulfate-mediated visible light photocatalytic performance

In this study, to improve peroxymonosulfate (PMS)-mediated visible-light photocatalytic performance of g-C3N4 in antibiotics degradation and elucidate its mechanism, an ultrathin Co3O4 nanomeshes/g-C3N4 nanosheets 2D Z-scheme heterojunction composite (x% Co3O4/g-C3N4) was successfully prepared calcining the mixtures of MOF-Co ultrathin nanosheets and g-C3N4. This unique nanomeshes/nanosheets structure with large SSA (153.92 m2/g) possessed an abundance of accessible active sites and large area intimate interfaces between Co3O4 and g-C3N4, thus remarkably promoting the separation and transport of charge carriers. The as-prepared optimal 10% Co3O4/g-C3N4 composites exhibited excellent degradation efficiency toward tetracycline (TC) under visible light irradiation and were further enhanced with the addition of PMS. The mechanism of the enhanced TC degradation in Co3O4/g-C3N4/Vis/PMS system was investigated in detail based on the characterization of the catalysts, TC degradation efficiency assessment, electron paramagnetic resonance (EPR) measurements, and reactive oxygen species (ROSs) quenching results. The TC degradation pathway was proposed based on the intermediates identified by the gas chromatography-mass spectrometer (GC–MS) measurements. This study provides a facile and promising path for the remediation of contaminated water via PMS mediated photocatalysis over highly active g-C3N4-based catalysts.

NixCo1-xS as an effective noble metal-free cocatalyst for enhanced photocatalytic activity of g-C3N4

Solar photocatalysis, as a method of green energy production and sustainable technology, has been regarded as one of the most effective strategies to resolve environmental issues and the current energy crisis. In this work, intimate contact hollow NixCo1-xS polyhedron/g-C3N4 nanosheet composites were prepared in-situ through a facile one-step hydrothermal method. The as-prepared NixCo1-xS/g-C3N4 composites showed superior photocatalytic activity and high stability for H2 generation and methyl orange (MO) degradation under visible light irradiation. The optimized 4 wt.% NixCo1-xS/g-C3N4 composite attained a maximum H2 evolution rate of 1420 μmol g–1 h–1, which was about 157 times higher than that of pure g-C3N4. In addition, the NixCo1-xS/g-C3N4 composite also exhibited greatly improved photocatalytic activity for dye degradation, which for MO was at 98.14 % in 9 min. The outstanding photocatalytic performance was predominantly attributed to the unique architecture of hollow NixCo1-xS polyhedrons, which not only provided more active sites at the edges and surface as convenient charge transfer channels, but also promoted the separation and transport of electron-hole pairs. This work provides some novel ideas for the design and development of highly efficient noble metal-free cocatalyst/semiconductor systems for photocatalytic H2 generation and dye degradation.

Ultrasound-Assisted Hydrothermal Fabrication of AgI/MFeO3/g-C3N4 (M = Y, Gd, La) Nano Sheet–Sphere–Sheet Photocatalysts with Enhanced Photodegradation Activities for Norfloxacin

AgI/MFeO3/g-C3N4 (M = Y, Gd, La) nano sheet–sphere–sheet photocatalysts were synthesized by a simple ultrasound-assisted hydrothermal approach. We characterized the microstructure, surface morphology, and optical absorption capacity of the obtained samples. According to the characterization results, AgI/MFeO3/g-C3N4 (M = Y, Gd, La) nano sheet–sphere–sheet photocatalysts were successfully obtained. MFeO3 nanospheres and AgI nanosheets were dispersed evenly on the surface of g-C3N4 nanosheets. AgI/MFeO3/g-C3N4 showed remarkable photocatalytic. Especially, 95% of NOF was photodegradated over AgI/LaFeO3/g-C3N4 within 3 h and the higher photocatalytic performance still remained after six cycles. Additionally, The N2 adsorption–desorption isotherms of AgI/MFeO3/g-C3N4 showed that AgI/LaFeO3/g-C3N4 possessed the highest specific surface area (79.32 m2/g). The result of scavenging experiment revealed that ·O2−, h+, and ·OH were the main roles in the photodegradation process. Benefitting from the nice energy band matching, MFeO3 acted as the center of photogenerated electrons migration and separation provided more direct electron channels. This work proposes an effective approach for the design and configuration of dual Z-scheme photocatalysts to accomplish the removal of organic contaminants based on g-C3N4.

Research on synthesis and photocatalytic activity of ZnFe2O4/Ag/g-C3N4 nanosheets composites

ABSTRACT A new ZnFe2O4/Ag/g-C3N4 nanosheets composite was synthesized by thermal polymerization combined with photoreduction and solvent thermal followed by calcination. The structure specification, surface composition, and optical absorption properties of as-prepared photocatalysts were characterized by X-ray diffraction, XPS (X-ray photoelectron spectroscopy) spectrum; transmission electron microscopy and UV-vis diffuse reflectance spectroscopy. The photocatalytic activity of the as-prepared photocatalysts was demonstrated by degradation of rhodamine B (RhB) solution under xenon lamp irradiation. It was confirmed by chemical capture experiments that ·O2 – and h+ are the main active species in the degradation of Rhodamine B. The unique Z-scheme structure of ZnFe2O4/Ag/g-C3N4 has been the basis for enhanced photocatalytic activity. The newly synthesized catalyst has better photocatalytic activity, good safety, and easy recycling.