C3N4 Phase Research Articles

One step synthesis of novel Cu3N/Cu2O/C3N4/Cu composite and their photocatalytic reduction activities

Copper nitride/cuprous oxide/carbon nitride/copper (Cu3N/Cu2O/C3N4/Cu) composite material was synthesized by one step thermal decomposition of copper-melamine complexes under N2 atmosphere. The as-synthesized powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS). The XRD analysis showed the mix phase of Cu3N, Cu2O, C3N4 and Cu. The photocatalytic activities of Cu3N/Cu2O/C3N4/Cu composite photocatalysts were evaluated by testing the photoreduction of chromium (VI) under UV–visible light irradiation. The results indicated that the synthesized samples are attractive photocatalysts for reduction of chromium (VI) under UV light irradiation. The photoreduction efficiencies of Cu3N/Cu2O/C3N4/Cu composite at 550 °C with TEOA induced by UV light within 120 min were 92.03 % caused by charge diffusion at the Cu3N/Cu2O/C3N4/Cu interface. The results indicated that the synthesized samples are attractive photocatalysts for reduction of chromium (VI) under UV light irradiation.

Highly Crystalline Poly(heptazine imide)-Based Carbonaceous Anodes for Ultralong Lifespan and Low-Temperature Sodium-Ion Batteries.

Carbon nitrides with layered structures and scalable syntheses have emerged as potential anode choices for the commercialization of sodium-ion batteries. However, the low crystallinity of materials synthesized through traditional thermal condensation leads to insufficient conductivity and poor cycling stability, which significantly hamper their practical applications. Herein, a facile salt-covering method was proposed for the synthesis of highly ordered crystalline C3N4-based all-carbon nanocomposites. The sealing environment created by this strategy leads to the formation of poly(heptazine imide) (PHI), the crystalline phase of C3N4, with extended π-conjugation and a fully condensed nanosheet structure. Meanwhile, theoretical calculations reveal the high crystallinity of C3N4 significantly reduces the energy barrier for electron transition and enables the generation of efficient charge transfer channels at the heterogeneous interface between carbon and C3N4. Accordingly, such nanocomposites present ultrastable cycling performances over 5000 cycles, with a high reversible capacity of 245.1 mAh g-1 at 2 A g-1 delivered. More importantly, they also exhibit an outstanding low-temperature capacity of 196.6 mAh g-1 at -20 °C. This work offers opportunities for the energy storage use of C3N4 and provides some clues for developing long-life and high-capacity anodes operated under extreme conditions.

Exploiting the combined power of C3N4/Ti3C2/Gd2O3 nanocomposites for advanced ciprofloxacin and pathogen degradation in wastewater

Using a solvothermal method, C3N4/Ti3C2/Gd2O3 (CN-TC/GdO) nanocomposites were synthesised and characterised using various methodologies. In the composite material, the XRD analysis revealed the presence of C3N4, Ti3C2 and Gd2O3 phases. The SEM and TEM images confirmed that nanocomposites with a homogenous and compact structure were successfully synthesised. UV-Vis spectroscopy revealed that the nanocomposites exhibited outstanding visible region absorption, which is advantageous for photocatalytic applications. Using ciprofloxacin as a model pollutant, the photocatalytic activity of the nanocomposites was evaluated, and the results indicated that the CN-TC/GdO nanocomposites exhibited substantially enhanced degradation efficiency compared to the individual components. The increased photocatalytic activity can be attributed to the synergistic effects of the three components, which function as efficient electron acceptors and donors and provide surface area and charge transfer pathways. Antibacterial activity was observed in CN-TC/GdO nanocomposites. These results indicate that CN-TC/GdO nanocomposites have tremendous potential as a photocatalytic material for the removal of ciprofloxacin from aqueous solutions and antibacterial research.

Synthesis of novel nanocomposite of g-C3N4 coated ZnO–MoS2 for energy storage and photocatalytic applications

Fabrication of heterostructures for energy storage and environmental remedial applications is an interesting subject of research that has been undertaken in this present investigation. The incorporation of g-C3N4 into ZnO:MoS2 heterojunction nanocomposite was accomplished by wet-chemical route and characterized by various techniques to ascertain its structure, morphology, and study its potential electro-optical characteristics. The g-C3N4@ZnO:MoS2 sample was investigated by x-ray diffraction (XRD) which reveals the co-existence of the ZnO, MoS2 and C3N4 phases linked to characteristic crystallographic planes in the spectrum, validating the formation of ternary nanocomposite. The XRD patterns of the pristine samples were also considered as reference to understand the structural evolution and phase transformations. Field emission scanning electron microscopy (FESEM) study states the formation of heterogeneous nanostructures having nanoparticles embedded on 2-D nanosheets like structures. Studies using energy dispersive spectroscopy (EDS) and elemental mapping show that all the elements that are linked to the above hybrid nanocomposite are present. Transmission electron microscopy (TEM) provided clear insights on the microstructure as we can identify the distribution of ZnO and MoS2 nanostructures on layered g-C3N4 nanosheets. The chemical composition and oxidation states of elements were elucidated by X-ray photoelectron spectroscopy (XPS) study, which added another layer of confirmation on the structural evolution of the ternary nanocomposite. Fourier transformed infrared (FTIR) study revealed the layered structure of sp2 hybridized bonding features of C and N in g-C3N4, besides Zn–O and Mo–S stretching vibrations. The nanocomposite demonstrated improved photodegradation efficacy and decomposed alizarin red and methylene blue dyes significantly with better stability and reusability. MoS2 as a co-catalyst acts as an electron acceptor/accelerator in the Z-scheme composite photocatalysis leading to improved photocatalytic efficiency. The resulting heterostructured material delivered a higher specific capacitance of 10.85 F/g with good capacitance retention. Electrochemical study revealed the energy storage capability of the hybrid system.

Understanding the effective breakdown of PAH s in water through the use of g–C3N4–Ag–Cu–Ni nanocomposites

The research work aimed to explore the suitability of using a novel g- C3N4–Ag–Cu–Ni nanocomposite for the simultaneous degradation of pyrene in wastewater. The outcome revealed that the g- C3N4 phase was successfully fabricated on the g–C3N4–based compound, and the existence of the g- C3N4-based compound beneficially stabilized the Ag–Cu–Ni particles. The g- C3N4–Ag–Cu–Ni nanocomposite demonstrated excellent performance in pyrene degradation under various conditions. The degradation of pyrene increased with a rise in the dosage of g- C3N4–Ag–Cu–Ni. These findings indicate that the g- C3N4–Ag–Cu–Ni nanocomposite could be a promising material for water purification, especially for the simultaneous photocatalytic and antimicrobial treatment of contaminated water bodies. The study provides a helpful guide for future research in this field.

Hydrogen production on g-C3N4 nanoflakes via photoelectrochemical water splitting

Graphitic carbon nitride (g-C3N4) is an emerging non oxide wide band gap semiconductor which has been investigated for hydrogen production through photoelectrochemical (PEC) water splitting. In this study, g-C3N4 nanoflakes film was fabricated by the thermal pyrolysis process and its PEC water splitting performance was investigated. The nanoflakes morphology and graphitic phase of C3N4 with an average crystallite size of 8.49 nm were confirmed with FESEM and XRD analysis respectively. A UV–visible spectrophotometer was used to estimate the band gap of the fabricated photoanode film (2.7 eV). Furthermore, the fabricated g-C3N4 film has shown a significant photocurrent density of 0.87 µA/cm2 under UV light illumination.

On the electronic properties and catalytic activity of MoS2–C3N4 materials prepared by one-pot reaction

MoS2–C3N4 composite materials with Mo content from 0.3 to 9 wt% have been prepared by means of one-pot synthesis from ammonium thiomolybdate (NH4)2MoS4 and urea-thiourea mixture. The solids were characterized by several physical techniques and tested in the thiophene hydrodesulfurization model reaction (HDS) and in photocatalytic hydrogen evolution reaction (PHER). Transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS) show that even at the smallest Mo contents the solids contain individual MoS2 and C3N4 phases. As attested by powder X-ray diffraction (XRD), addition of (NH4)2MoS4 impacts the properties of obtained C3N4, probably at the growth stage, leading to more disordered carbon nitride phase. However, the materials demonstrate electronic properties close to a superposition of two separate MoS2 and C3N4 phases, as follows from the results of UV–visible diffuse reflectance spectroscopy (UV–vis DRS) combined with Ultraviolet and X-ray photoelectron spectroscopies (UPS, XPS). The band alignment diagram constructed from the UV–vis DRS, XPS and UPS data is of staggered type, the valence band edge of MoS2 being located above that of C3N4. Composite materials have high thiophene HDS activity, increasing in step with the Mo content, which proves fine dispersion of MoS2 phase and good availability of MoS2 edges to the reactants. By contrast, PHER activity first increases and then decreases with the Mo loading, reflecting on the competition between the ability of MoS2 to promote associative desorption of hydrogen and its role as a charge carriers recombination sink.

Changes in Structural, Morphological and Optical Features of Differently Synthetized C3N4-ZnO Heterostructures: An Experimental Approach

C3N4 is an innovative material that has had huge success as a photocatalyst in recent years. More recently, it has been coupled to robust metal oxides to obtain more stable materials. This work is focused on the different synthesis techniques used to prepare bare C3N4 and combined C3N4/ZnO mixed systems. Different precursors, such as pure melamine and cyanuric acid-based supramolecular complexes, were employed for the preparation of the C3N4 material. Moreover, different solvents were also used, demonstrating that the use of water leads to the formation of a more stable heterojunction. Structural (XRD), morphological (FESEM) and optical (UV-vis) measurements underlined the role of the precursors used in the preparation of the materials. A clear trend can be extrapolated from this experimental approach involving different intimate contacts between the two C3N4 and ZnO phases, strictly connected to the particular preparation method adopted. The use of the supramolecular complexes for the preparation of C3N4 leads to a tighter association between the two phases at the heterojunction, resulting in much higher visible light harvesting (connected to lower band gap values).

Effect of Nitrate via CVD Coating on Hydrogen Embrittlement in High Strength Steel Treated with Zinc PVD Coating

High strength low alloy steel (HSLAS) is quite sensitive to hydrogen embrittlement due to its different phases. This study investigated the hydrogen embrittlement (HE) behavior of uncoated, physically vapor deposition (PVD) coated, and chemically vapor deposition (CVD) coated HSLAS. The XRD indicates the formation of ZnO, Zn(N3)2, γN and C3N4 phases at the outer coating layer. The results show that combination of surface nitriding and zinc deposition are efficient method against hydrogen embrittlement. This could be attributed to the reduction of hydrogen that is generated by the reaction of surface Zn) N3)2 phase and the low rate of hydrogen transport through the γN phase. The coatings were tested by immersing the tensile samples in a diluted H2SO4 solution with water for 24 hours. Additionally, the result shows that combined coating resulting in higher tensile strength, yield stress, and tensile elongation compared to uncoated samples. Hardness results indicate that the combined coatings (PVD + CVD) has the higher value of about 258 HV, followed by the uncoated sample of about 218 HV, while the PVD only coated sample have the lower hardness value of about 175 HV.

Recent Progress in Polymorphs of Carbon Nitride: Synthesis, Properties, and Their Applications.

Carbon nitride (CN) materials are at the forefront of contemporary solar energy conversion applications, owing to their extraordinary physicochemical properties. Having such multifunctional properties, CN photocatalytic materials are practically significant; however, due to the indistinguishable physical properties, all solid CN materials in most literature reports are referred to as graphitic C3 N4 phase, which is incorrect. This perspective discourses the various identified polymeric forms of CN, their molecular structure, synthesis, photophysical properties, and their applications. The article attempts to simplify the conjectures in CN terminology and discuss future perspectives, challenges, and opportunities in the developing field of CN chemistry.

Cobalt-Based Multicomponent Oxygen Reduction Reaction Electrocatalysts Generated by Melamine Thermal Pyrolysis with High Performance in an Alkaline Hydrogen/Oxygen Microfuel Cell.

A series of cobalt-based multicomponent electrocatalysts (Co-Cat-T) for the oxygen reduction reaction (ORR) were synthesized by thermal pyrolysis of activated carbon-supported cobalt and melamine mixture from 500 to 800 °C. Their corresponding electrocatalytic performance was systematically investigated toward ORR in an alkaline electrolyte. The electrocatalyst chemical composition and structure evolution (e.g., microstrain, crystallite size, and cell volume) were confirmed by X-ray diffraction Rietveld analyses. The material generated at 550 °C (Co-Cat-T550) showed the largest cell volume of the C3N4 phase with a crystallite size of 4.1 ± 0.1 nm. Independent of the heat-treatment temperature, the cobalt atom was coordinated to nitrogen moieties. The following findings: cobalt inserted in the carbon nitride framework (Co-g-C3N4), abundant Co-Nx and pyridinic-N species, unique encapsulated cross-tubular structure, and disordered carbon domains performed better in the ORR with Co-Cat-T550 among the obtained electrocatalysts. In addition, Co-Cat-T550 showed performance comparable to Pt/C in an alkaline hydrogen/oxygen microfuel cell platform.

Shock-induced phase transition of g-C3N4 to a new C3N4 phase

In this study, phase transition of graphitic carbon nitride (g-C3N4) was investigated using the shockwave compression technique. Firstly, the shock Hugoniot data of g-C3N4 were obtained using a bore propellant gun and a light gas gun under impact velocities of 1.208–4.982 km/s, revealing one phase transition pressure of g-C3N4 at 22.4 GPa. Then, a series of shock recovery experiments was carried out with a pressure range of 17.0–62.1 GPa. The recovered samples were characterized by various techniques, including X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The measured d-values of the recovered samples were compared with those from the previous reported results, revealing a new carbon nitride phase synthesized by the shockwave compression technique. The new phase is indexed as a triclinic cell with a = 0.481 nm, b = 0.353 nm, c = 0.285 nm, α = 67.52°, β = 100.75°, γ = 106.47°, and Vcell = 0.043 nm3. EDX and XPS spectra reveal the existence of C and N elements with an atomic ratio of 0.754, also confirming the presence of a new C3N4 phase obtained via a g-C3N4 phase transition induced by shockwave compression with a pressure range of 29.3–62.1 GPa. These sample results are in good agreement with the shock Hugoniot data.

Organic nitrogen promotes stability of metallic catalysts in conversion of bamboo pulp to low carbon polyols

Abstract Herein, the synthesis and performance of a novel and stable catalyst capable of facile hydrolysis of bamboo pulp were reported. Based on adopting complex agent to have a complex reaction with Ni2+ cations, the graphitic g-C3N4 phase and nitride phases were formed eventually. The interaction among metals and C, N atoms was analyzed by XRD and XPS. Some Ni-W alloys (mainly NiWO4 was included) were formed besides metallic Ni0 and tungsten species characterized. Particles on the surface of 15%Ni-20%W/MBC@M-0.25 catalyst exhibited homogeneous distribution and surrounded by disordered C3N4 layer characterized by TEM. Besides, the organic N sources were decomposed and the C3N4 phase with high hydrothermal property was formed simultaneously. For catalytic efficiency, 15%Ni-20%W/MBC@M-0.25 catalyst acquired the highest EG yield of 55.8% compared to 36.9% via 15%Ni-20%W/MBC catalysts. The carbon supports and organic nitrogen sources demonstrated great influence on catalytic efficiency. Catalyst recycle experiments implied that Ni-W/MBC@M-0.25 could remain relative stable under this catalytic reaction condition. The Ni-W alloys and the C3N4 phase were deduced as the main contributors to maintain the catalyst stability.

Novel rugby-ball-like Zn3(PO4)2@C3N4 photocatalyst with highly enhanced visible-light photocatalytic performance

An interesting rugby-ball-like Zn3(PO4)2@C3N4 photocatalyst with well- controlled structures as high-efficient visible-light photocatalysts was synthesized via two steps of solvothermal-grinding calcination method. The composition, structure, morphology, and optical absorption properties of as-synthesized Zn3(PO4)2@C3N4 samples were intensively characterized by XRD, N2 physical adsorption, SEM, TEM, FT-IR, UV–vis DRS, XPS, PL and photoelectrochemical measurements, respectively. The formation of C3N4 shell obviously increased the surface area and induced the rich pore structures. The intimate interface between Zn3(PO4)2 and C3N4 phase obviously enhanced the transport rate of photogenerated carriers and restrained the recombination of photogenerated electrons and holes. The optimal Zn3(PO4)2@C3N4 (35 wt%) exhibited the highest adsorption and photocatalytic activity in the degradation of methylene blue (MB), which was 150 and 7.5 times as high as C3N4, respectively. Moreover, the robust Zn3(PO4)2@C3N4 nanoheterojunctions fabricated by this grinding-calcination route have high stability in recycling reactions.

Structural, mechanical, electronic, and thermodynamic properties of dense B3N4 under high pressure predicted from first principles

Five dense B3N4 structures are established by substitution of C atoms with B atoms in the five hypothetical dense C3N4 phases. The structural, elastic, and electronic properties of the five B3N4 polymorphs are investigated through the first‐principles calculations. Our calculations indicate that c‐B3N4 is energetically favorable in the five structures. Through the calculations of formation enthalpy, we conclude that the B3N4 polymorphs are thermodynamically stable at zero pressure except for the cs‐B3N4. The elastic moduli of the five B3N4 polymorphs are calculated using the Voigt–Reuss–Hill approximation. The calculated bulk modulus of cs‐B3N4 (337 GPa) is the highest of them. The c‐B3N4, with shear modulus of 248 GPa, might be a potentially ultra incompressible and hard material. By the elastic stability criteria, it is predicted that the cs‐B3N4, c‐B3N4, and p‐B3N4 are mechanically stable within 100 GPa, while the β‐B3N4 and α‐B3N4 become mechanically unstable when pressure increases to 30 and 80 GPa, respectively. The calculated B/G ratios indicate that cs‐B3N4 and p‐B3N4 possess a ductile nature within 100 GPa. The c‐B3N4 possess a brittle nature at 0 GPa, as it begins to be prone to ductility, when the pressure increases to 90 GPa. The calculated band structures and densities of states show that all the five B3N4 phases are insulative. Through the quasiharmonic Debye model, we also investigated the thermodynamic properties of these B3N4 polymorphs.

Synthesis of Ultra-incompressible sp3-Hybridized Carbon Nitride with 1:1 Stoichiometry

The search of compounds with CxNy composition holds great promise for creating materials which would rival diamond in hardness due to the very strong covalent C–N bond. Early theoretical and experimental works on CxNy compounds were based on the hypothetical structural similarity of predicted C3N4 phases with known binary A3B4 structural types; however, the synthesis of C3N4 other than g-C3N4 remains elusive. Here, we explore an “elemental synthesis” at high pressures and temperatures in which the compositional limitations due to the use of precursors in the early works are substantially lifted. Using in situ synchrotron X-ray diffraction and Raman spectroscopy, we demonstrate the synthesis of a highly incompressible Pnnm CN compound (x = y = 1) with sp3-hybridized carbon above 55 GPa and 7000 K. This result is supported by first-principles evolutionary search, which finds that CN is the most stable compound above 14 GPa. On pressure release below 6 GPa, the synthesized CN compound amorphizes, maintaining...

Two Novel C₃N₄ Phases: Structural, Mechanical and Electronic Properties.

We systematically studied the physical properties of a novel superhard (t-C3N4) and a novel hard (m-C3N4) C3N4 allotrope. Detailed theoretical studies of the structural properties, elastic properties, density of states, and mechanical properties of these two C3N4 phases were carried out using first-principles calculations. The calculated elastic constants and the hardness revealed that t-C3N4 is ultra-incompressible and superhard, with a high bulk modulus of 375 GPa and a high hardness of 80 GPa. m-C3N4 and t-C3N4 both exhibit large anisotropy with respect to Poisson’s ratio, shear modulus, and Young’s modulus. Moreover, m-C3N4 is a quasi-direct-bandgap semiconductor, with a band gap of 4.522 eV, and t-C3N4 is also a quasi-direct-band-gap semiconductor, with a band gap of 4.210 eV, with the HSE06 functional.

Raman spectroscopy of melamine at high pressures up to 60 GPa

In this work, the Raman scattering of melamine was studied under high pressure up to 60 GPa. The behavior of the most intensive peaks of the Raman spectrum of melamine, 677 cm−1 and 985 cm−1 modes, and their line widths do not show any phase transition or indication of formation of sp 3 bonds. Comparing the behavior of the line width of the Raman peaks of graphite under pressure and that of melamine leads us to conclude that the s-triasine (C–N) ring is more rigid than the C–C graphite ring. High pressure results with melamine suggest that the direct phase transition g-C3N4 to dense C3N4 phase should occur above 60 GPa.

Elastic and inelastic behavior of graphitic C3N4 under high pressure

We conducted high pressure measurements on the graphitic C3N4 (g-C3N4) phase using Brillouin light scattering (BLS) up to 41.5GPa and X-ray Raman scattering (XRS) up to 26GPa to probe the behavior of sp2 bonds. Analysis of the BLS and XRS measurements of g-C3N4 reveals no structural phase transition and, unlike graphite, no sp2 to sp3 rehybridization in this pressure range. From the BLS results we estimate the ambient condition longitudinal velocity (VL=6.27±0.12km/s), aggregate shear wave velocity (VS=3.04±0.2km/s), and the shear (μ=21.6GPa) and bulk elastic moduli (KV=63.1GPa) of the g-C3N4.

Analysis of the dynamic synthesis superdispersed product in a C-N system by high resolution electron microscopy

We report on the results of analysis of the superdispersed product synthesized in a superfast jet of electric-discharge carbon plasma flowing to the nitrogen atmosphere. The data obtained by high resolution transmission electron microscopy indicate the presence of the α phase of hypothetic carbon nitride C3N4 in the form of unique quasi-two-dimensional multilayer particles.