g-C3N4 Nanolayers Research Articles

A New Design to Enhance the Enzyme Activities: Investigation of L-Asparaginase Catalytic Performance by IMAC Effect on g-C3N4 Nanolayers

A New Design to Enhance the Enzyme Activities: Investigation of L-Asparaginase Catalytic Performance by IMAC Effect on g-C3N4 Nanolayers

Promoted photocatalytic hydrogen evolution via double-electron migration in Ag@g-C3N4 heterojunction

The unsaturated edge Ag introduced on the surface of photocatalysts plays an important role in boosting photo-excited electrons for the photoreduction H2O reaction. However, a moderate and tractable strategy to efficiently expose edge Ag remains an enormous challenge. For this purpose, a core skeleton with ‘Ag conductive nanosphere array’ inside and a two-dimensional sheet structure with g-C3N4 layer outside are formed. The introduction of Ag nanospheres into g-C3N4 not only enlarges the distance between g-C3N4 nanolayers, but also increases the exposure of Ag nanospheres. When Ag intimately contacts with g-C3N4, the electrons of g-C3N4 voluntarily flow to the Ag. Consequently, a built-in electric field (IEF) has been formed at interface of Ag@g-C3N4 heterojunction, which prevents the continuous flow of electrons from g-C3N4 to Ag. Under irradiation, the e− accumulated in Ag tend to recombine with the h+ in the valence band of g-C3N4 which is driven by Coulomb interaction and IEF. Ag nanospheres are fabricated as a co-catalyst to decorate the g-C3N4 nanolayer, which hinder the conglomeration of g-C3N4 nanolayers. Moreover, Ag@g-C3N4 heterojunction provides polyunsaturated edge Ag as active sites, inducing prolonged lifetime of photogenerated electrons and formed the unique charge transfer channels. In addition, abundant nitrogen vacancies are formed, which strengthens the chemisorption of H2O. As a result, supreme Ag@g-C3N4 realizes a high H2 evolution of 312.5 μmol and preserves a good sustainability. This paper emphasizes the importance of unique electron transfer pathway and chemisorption of water for photoreduction H2O.

Snowball flower-like g-C3N4/ZnFe2O4 mesoporous hollow microspheres with enhanced triethylamine sensing properties

Herein, the snowball flower-like g-C3N4/ZnFe2O4 mesoporous hollow microspheres, in which two-dimensional (2D) g-C3N4 nanolayers were loaded onto the surface of ZnFe2O4 hollow microspheres, were constructed by a simple solid phase reaction. The effect of the g-C3N4 concentration on the structure, morphology and gas-sensing performance of the g-C3N4/ZnFe2O4 composites had been explored. On the basis of gas sensitivity test results, the composites owned lower working temperature (160 ℃) and better selectivity toward TEA in comparison with pure ZnFe2O4. Notably, the sensor based on the g-C3N4/ZnFe2O4-15 hollow microspheres (adding 15 ml of g-C3N4 aqueous solution) exhibited outstanding sensing properties, including superior response (18.3) toward 100 ppm TEA at optimum work temperature of 160 ℃, speedy response-recovery time (33, 30 s) and outstanding stability. And the sensor maintained high response of 4.3 to low concentration TEA (5 ppm). The improved gas-sensing performance of the composites could be attributed to the porous ZnFe2O4 hollow microspheres loaded by 2D g-C3N4 nanolayers with large specific surface area and the heterostructure formed between them. Hence, a potential application of the g-C3N4/ZnFe2O4 microspheres might be achieved in detecting TEA at a low optimum work temperature.

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

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

Bi2O3/ g-C3N4 nanocomposites as proficient photocatalysts for hydrogen generation from aqueous glycerol solutions beneath visible light

A sequence of Bi2O3/g-C3N4 nanocomposites with diverse Bi2O3 content (0.5–5 molar %) has been synthesized by the sonication-mixture method using mesoporous β-Bi2O3 and g-C3N4 and utilized as efficient photocatalysts for hydrogen generation from aqueous glycerol solutions beneath visible light irradiation. Mesoporous Bi2O3 particles were effectively integrated at the exterior of two-dimensional (2D) g-C3N4 nanolayers producing effective heterojunctions that facilitate the charge transference amongst g-C3N4 and Bi2O3 and minimize the recombination of photocharges. The number and efficiency of the heterojunctions in the Bi2O3/g-C3N4 nanocomposites depend on the Bi2O3 amount, reaching the optimal development at 3.0 molar % of Bi2O3. The maximum H2 production was then obtained on the 3.0% β-Bi2O3/g-C3N4 nanocomposite that achieves a production (8600 μmol g−1) 20-fold greater than that obtained on bare β-Bi2O3 and g-C3N4 counterparts. The improvement in the photoactivity of Bi2O3/g-C3N4 nanocomposites was analyzed taking into account the differences in the capability of the nanocomposites to fascinate visible light and the efficiency of detaching the photoinduced charges derived from the different Bi2O3 content in the nanocomposites.

Efficient solar-light-driven photoelectrochemical water oxidation of one-step in-situ synthesized Co-doped g-C3N4 nanolayers

Cobalt-doped g-C3N4 (Co-g-CN) nanolayers were prepared by a single-step thermal treatment with urea and cobalt nitrate. Different amounts of cobalt nitrate were tested to optimize the amount of cobalt dopant in the g-C3N4 (g-CN) matrix. Several characterization methods were used to explore the structural and optical properties along with the photoelectrochemical (PEC) performance. X-ray diffraction and Fourier transform infrared studies confirmed that g-CN nanolayers were successfully doped with cobalt without disturbing the basic 2-D structure and tris-triazine units of g-CN. Furthermore, microscopy images demonstrated that the cobalt effectively transformed the short nanosheets into long nanolayers. The cobalt-doping enhanced the visible absorption of g-CN and tuned the bandgap from 2.71 to 2.62 eV. An X-ray photoelectron spectroscopy (XPS) investigation discovered that cobalt entered into the g-CN network as Co2+ ions. XPS valence band spectra gave information on the modification in the valence and conduction band edge potentials due to cobalt doping. The photoluminescence intensity from the Co-g-CN samples was lesser than that from g-CN nanosheets, and the PEC activity of the Co-g-CN nanolayers was greater than that of as-prepared g-CN nanosheets. Co-g-CN samples prepared with 15 mg of cobalt nitrate hexahydrate showed a PEC performance of 3.2522 mA/cm2, which was greater than that of g-CN nanosheets (1.9246 mA/cm2). The better PEC performance was ascribed to the synergistic consequence of the higher visible absorption obtained by tuning the bandgap and the host–guest interactions between cobalt and g-CN.

Efficient day-night photocatalysis performance of 2D/2D Ti3C2/Porous g-C3N4 nanolayers composite and its application in the degradation of organic pollutants

It is hindered by the limited light time that the development of photocatalysis technology, which is a clean and energy-saving advanced oxidation process. In this work, a 2D/2D Ti3C2/porous g-C3N4 nanolayers composited van der Waals (VDW) heterostructure photocatalyst (Ti3C2/PCN) was prepared by a straightforward vacuum filtration method after an ultrasonic stripping process. In this Ti3C2/PCN composite photocatalyst, PCN nanolayers play the role of absorbing visible light, while Ti3C2 nanolayers form VDW heterojunction with PCN nanolayers, which is beneficial to migration of photo-generated electrons from PCN to Ti3C2. The band structure match of Ti3C2/PCN and the build-in electric field from the VDW heterojunction both favor the effective separation and migration of photo-induced charge carriers that is why the Ti3C2/PCN composite shows good day-photocatalytic capability with 98% phenol removal efficiency. Besides, as a good electronic storage material, the Ti3C2 can store excess photo-generated electrons under light irradiation and release them when exposed to electron acceptors in the dark condition. Therefore, the night-photocatalysis can work out even without sunlight, in which 32% phenol was decomposed. In addition, the universality of Ti3C2/PCN day-night photocatalytic system is proved by the degradation of various organic pollutants. The design of this day-night photocatalyst can facilitate the application of photocatalytic reaction to actual environmental scenes, since it reduces the limitation imposed by the presence or absence of sunlight.

Superior uniform carbon nanofibers@g-C3N4 core-shell nanostructures embedded by Au nanoparticles for high-efficiency photocatalyst

Ultrathin g-C3N4 nanolayers were uniformly assembled on Au nanoparticles (NPs) decorated carbon nanofiber (CNFs) by a facile gas-solid approach. The mean thickness of g-C3N4 shell layers on CNFs-Au supports was about 22.5 nm. The ternary system of as-prepared photocatalysts with superior uniformly core-shell nanostructures present enhanced photocatalytic properties. The rate constants (rhodamine B and K2Cr2O7) of CNFs-Au@g-C3N4 were about 3.5 and 4.5 times of g-C3N4 powders, respectively. While the rate of H2-evolution was 2.3-fold of the physical mixture, when the loading amount of Au NPs was about 0.52 At.%. Their excellent photocatalytic activities were attributed to the advantages of their unique core-shell nanostructures and the synergy of the Au NPs as a high-efficiency electron conduction bridge and their surface plasmon resonance (SPR) effect. Moreover, the ternary systems of CNFs-Au@g-C3N4 present the gratifying cycling stability in photocatalytic reactions due to their ultra-long core-shell nanostructures. Our work provides a novel route for designing and constructing multicomponent photocatalyst in wastewater treatment and solar energy applications.

Fast and ultra-sensitive voltammetric detection of lead ions by two-dimensional graphitic carbon nitride (g-C3N4) nanolayers as glassy carbon electrode modifier

Recently, graphitic carbon nitride (g-C3N4) has attracted great interest for photo(electro)chemical applications such as sensing, solar energy exploitation, photocatalysis, and hydrogen generation. This paper presents the potential application and benefits of g-C3N4 nanolayers as a green and highly efficient electrode modifier for the detection of trace lead ions in drinking water and urban dust samples. Carbon nitride nanosheets with a thickness of ∼6 A° and lateral of 100–150 nm were prepared through high-temperature polymerization of melamine followed by sonication-assisted liquid exfoliation. A glassy carbon electrode (GCE) was modified by a thin layer of g-C3N4 through drop casting and used for fast and sensitive (ppb range) detection of lead ions. It is shown that the g-C3N4 nanosheets have a total specific area of about 45 m2/g, causing an increase in the microscopic surface area of GCE by a factor of 20 in comparison to the bar electrode; hence, enhanced peak current intensity in voltammetric studies is attained. Differential pulse anodic stripping voltammetry indicates two linear anodic stripping responses of 2.4–7.5 ng mL−1 (R2 = 0.983) and 10.0–1000.0 ng mL−1 (R2 = 0.993). These ranges fulfill the requirements of the U.S. EPA and WHO standards for the quality control of drinking water. Measurements on urban dusts and drinking water also indicate the potential of the modified electrode for fast and ultrasensitive detection of lead ions in real samples. The advantages and figure of merit of the developed electrode for lead sensing are addressed.

Enhanced hydrogen production by the protonated, sulfur doped and Pt-loaded g-C3N4 nanolayers

Chemically modified graphitic carbon nitride (g-C3N4) nanolayers have been developed with simultaneous modifications through protonation, sulfur-doping and Pt-loading. The obtained materials have been extensively studied for their structural, morphological, optical, surface area, photocurrent density, impedance and photocatalytic hydrogen production properties under solar light irradiations. The synergistic effect of these modifications is found to increase their photocatalytic efficiencies into many folds. From the obtained results, the mechanism of the observed efficiency can be proposed as follows; (i) the protonation led to a stronger exfoliation of g-C3N4 from its bulk-structure to nanolayers, while (ii) the sulfur doping reduces the band gap energy through altering their band edge positions and (iii) the Pt-loading enhances the charge separation, which facilitated more number of electrons to reduce H+ ions into H2 molecules.

2D/2D g-C3N4/MnO2 Nanocomposite as a Direct Z-Scheme Photocatalyst for Enhanced Photocatalytic Activity

Constructing two-dimensional (2D) composites using layered materials is considered to be an effective approach to achieve high-efficiency photocatalysts. Herein, a 2D/2D g-C3N4/MnO2 heterostructured photocatalyst was synthesized via in situ growth of MnO2 nanosheets on the surface of g-C3N4 nanolayers using a wet-chemical method. The hybrid nanomaterial was characterized by a range of techniques to study its micromorphology, structure, chemical composition/states, and so on. The g-C3N4/MnO2 nanocomposite exhibited greatly improved photocatalytic activities for dye degradation and phenol removal in comparison to the single g-C3N4 or MnO2 component. On the basis of the electron paramagnetic resonance spectra, X-ray photoelectron spectra, and the Mott–Schottky measurements, we consider that a Z-scheme heterojunction was generated between the g-C3N4 nanosheets and MnO2 nanosheets, wherein the photoinduced electrons in MnO2 combined with the holes in g-C3N4, leading to enhanced charge carrier extraction and ut...

Sunlight-driven photocatalytic activity of SnO2 QDs-g-C3N4 nanolayers

Herein, we reported a sunlight driven photocatalyst, SnO2 quantum dots (QDs)-g-C3N4 nanolayers (NLs) for the abatement of water pollution. SnO2 QDs were prepared in the presence of g-C3N4 NLs and the average crystallite size of SnO2 QDs was achieved below 3 nm. The interactions between both SnO2 QDs and g-C3N4 NLs are strong, as established by differences in binding energies. The sunlight driven photocatalytic activity of SnO2-g-C3N4 composite was carried out by the degradation of methyl orange (MO) and it shows 94% degradation under sunlight within 180 min. The improved photocatalytic activity under sunlight is attributed to the synergetic effect of SnO2 QDs and layered g-C3N4.

The solution-phase process of a g-C3N4/BiVO4 dyad to a large-area photoanode: interfacial synergy for highly efficient water oxidation.

The oxygen evolution reaction (OER) is the rate-limiting process for water splitting, and highly efficient large-area OER photoanodes have been considered as an essential part in photoelectrochemical water splitting reactors. The high hole-electron separation efficiency of photoanodes is highly required for real applications of photoanodes in sufficiently harvesting solar energy. Herein we show that the inactive g-C3N4 nanolayers can be self-assembled with BiVO4 into a highly coupled BV/CN dyad to significantly enhance the charge separation efficiency of BiVO4 photoelectrodes for the OER. The incident photon-to-current conversion efficiency (IPCE) of visible light (400 nm) provided by the scalable BV/CN-5 photoanode was estimated to be 50% at 1.23 V vs. RHE in 0.5 M Na2SO4 solution and significantly increased to 97% at a bias voltage of 1.6 V vs. RHE.

Ultrathin graphitic C3N4 nanosheets as highly efficient metal-free cocatalyst for water oxidation

Here, we demonstrate that ultrathin graphitic-phase C3N4 nanosheets (g-C3N4-NS) could serve as an efficient metal-free cocatalyst for improving oxygen evolution activity on nanoporous BiVO4 photoanode. More specifically, as compared with pure BiVO4 photoanode, ultrathin g-C3N4 nanolayers not only suppress the surface charge recombination of BiVO4, but also effectively transfer and store holes for water oxidation. As expected, the ultrathin graphitic-phase C3N4 cocatalyst modified BiVO4 photoanode exhibited significantly improved photocurrent density and H2 generation capability, nearly 7 and 12 times with respect to the pristine BiVO4 under the same conditions. These results demonstrate an effective approach for the design and construction of low-cost and highly efficient PEC systems.