Nitride Materials Research Articles

Rational design of nitrogen-doped carbon for palladium catalysts in hydrogenation of hydrazo compounds

We synthesized CN11, a carbon nitride material rich in sp3 hybrid graphitic nitrogen (sp3-N), employing a facile oxalic acid-assisted melamine molecular assembly strategy. CN11 promoted the formation of Pd nanoparticles (NPs) predominantly exposing {200} facets, termed Pd/CN11-2. This facet-specific configuration significantly boosted hydrogen adsorption, leading to notable improvements in catalytic activity. Compared to Pd/XC-72-2 and Pd/g-C3N4-2, Pd/CN11-2 exhibited a remarkable two-fold and nineteen-fold increase in catalytic yield for hydrazo compound hydrogenation, respectively. Pd/CN11-2 also demonstrated robust performance across a range of reaction conditions, maintaining excellent yield. This study emphasizes the critical role of tailored support structures in controlling Pd NPs facets, thereby enhancing hydrogenation efficiency. It provides valuable insights for advancing the industrial application of Pd-based catalysts, underscoring the importance of strategic support modulation for optimizing catalytic performance.

Boosting the catalytic performance of carbon nitrides for overall water splitting by tuning the C/N ratio: A theoretical investigation

We systematically study the catalytic activity of carbon nitride materials by controlling the carbon-to-nitrogen ratio and engineering their morphological structure. The electrocatalytic activities of five types of carbon nitrides with different C/N ratios— C4N, C3N, C2N, CN, and C3N4 — toward the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are theoretically evaluated. The results show that the OER overpotential decreases as the nitrogen content increases, reaching its lowest value in CN. Our results highlight CN as a bifunctional electrocatalyst with acceptable performance with overpotentials of 0.76 and 0.05 V for OER and HER, respectively.

Development and Diagnostic Study of the RF nitrogen Atom Source

With the development of thin film technology, particularly the increasing demand for research on group III nitride materials, the need for N ions has significantly increased. A wider and more efficient RF nitrogen atom source specifically designed for nitride film growth has been developed. To evaluate the nitrogen atom density from the RF nitrogen source, a global model of RF nitrogen gas discharge plasma was created. This model was calibrated by measuring the emission spectrum of RF nitrogen gas discharge, and the relationships between nitrogen atom density and actual working pressure, power, and discharge chamber size were determined. It was found that the nitrogen atom density increases with increasing power and initially increases with pressure before decreasing. Finally, the nitrogen atom density was determined, achieving an 18% nitrogen atom dissociation rate and a nitrogen atom density of 5×1012/cm³ at an RF power of 400 W. This density is significantly higher than that of nitrogen ions, indicating that this is a nitrogen atom source with high purity.

Adenine-originated N-doped C3N4 modified glassy carbon electrode for ultra-sensitive electrochemical quantification of cysteamine drug

Cystinosis is a rare autosomal recessive illness in which cystine accumulates in lysosomes, causing crystallisation in important organs. Cysteamine, the only approved therapy, demands precise concentration control because of its therapeutic importance. Cysteamine detection methods, including fluorescence spectroscopy, chemical etching, and HPLC, need sophisticated sample preparation and expensive equipment. Electrochemical sensing provides a simpler alternative with higher sensitivity and selectivity. However, traditional carbon electrodes have limited sensitivity and detection limits. Nitrogen (N-CN), sulfur (S-CN), and nitrogen/sulfur co-doped (N, S-CN) graphitic carbon nitride materials were produced using a one-pot calcination of adenine and methionine precursors. N-CN-modified glassy carbon electrodes demonstrated higher electrocatalytic activity, quicker electron transfer, and increased selectivity, sensitivity, and stability for cysteamine detection. Structural and morphological characterisation of the synthesised materials was performed using various analytical techniques, including Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller plots, X-ray diffraction, and X-ray photoelectron spectroscopy. The sensor showed a linear relationship between anodic peak current and cysteamine concentration in the range of 0 µM to 1 mM, with a low detection limit of 82.5 nM (0.0825 µM). Moreover, the modified electrode exhibited good reproducibility and stability with a recovery rate of 95.5 % and a relative standard deviation (RSD < 5 %). Real-sample analysis revealed a good agreement between LSV and HPLC for detecting cysteamine in blood serum. The paper describes a unique metal-free N-CN synthesis utilising adenine, allowing effective electrochemical detection.

Thin film synthesis, structural analysis, and magnetic properties of novel ternary transition metal nitride MnCoN2

Recent high-throughput computational searches have predicted many novel ternary nitride compounds providing new opportunities for materials discovery in underexplored phase spaces. Nevertheless, there are hardly any predictions and/or syntheses that incorporate only transition metals into new ternary nitrides. Here, we report on the synthesis, structure, and properties of MnCoN2, a new ternary nitride material comprising only transition metals and N. We find that crystalline MnCoN2 can be stabilized over its competing binaries, and over a tendency of this system to become amorphous, by controlling growth temperature within a narrow window slightly above ambient condition. We find that single-phase MnCoN2 thin films form in a cation-disordered rocksalt crystal structure. X-ray photoelectron spectroscopy analysis suggests that MnCoN2 is sensitive to oxygen through various oxides and hydroxides binding to cobalt on the surface. X-ray absorption spectroscopy is used to verify that Mn3+ and Co3+ cations exist in an octahedrally coordinated environment, which is distinct from a combination of CoN and MnN binaries and in agreement with the rocksalt-based crystal structure prediction. Magnetic measurements suggest that MnCoN2 has a canted antiferromagnetic ground state below 10 K. We extract a Weiss temperature of θ=−49.7K, highlighting the antiferromagnetic correlations in MnCoN2. Published by the American Physical Society 2024

Sustainable photodegradation of tetracycline by surface-functionalized carbon nitride: Mechanism insight and toxicity assessment

Here, we report the facile preparation of amino- and vacancies-abundant carbon nitride photocatalyst using acetone as a low-boiling-point solvent and describe its successful performance of environmental purification. As a demonstration of the notion, tetracycline (TC) antibiotic as an emerging aqueous contaminant has been used as a model substrate for assessing the photoactivity of the modified carbon nitride and clarifying its intrinsic mechanism. 96 % of TC can be photocatalytically removed within 30 min, accompanied by a discernible mitigation in ecotoxicological impact. Reactive species, including •OH, •O2-, and photogenerated holes, are considered the critical oxidants. Meanwhile, the possible intermediates and transformation pathways of TC degradation were investigated utilizing the LC-MS technique, the Fukui function, and the T.E.S.T. software. The comprehensive approach furnishes valuable insights for assessing the evolutionary dynamics of tetracycline in an advanced oxidation process (AOP). This study offers a sustainable, cost-effective, and eco-friendly approach to preparing carbon nitride material, which is believed to open an avenue for the facile design of heterogeneous environmental photocatalysts and to provide insights into the various environmental applications.

Reduction of carbon dioxide to methane and ethanol on the surface of graphyne-like boron nitride (BNyen) monolayer: A DFT study

Recently, scientists have created a novel type of boron nitride material known as BNyen. This material is similar in structure to Graphyne and has a higher N:B ratio than traditional boron nitride due to the addition of boron and nitrogen connecting segments within its units. This material has been studied for its potential as a photocatalyst for reduction of CO2 using DFT approaches. Optical and electronic attributes of BNyen suggest that it has a wider visible-light range and a band gap of 5.69 eV. By adding boron to BNyen, patial distributions of LUMO and HOMO indicate that π network has been extended, resulting in significantly greater photocatalytic efficiency. Upon the adsorption of CO2 on BNyen monolayer, the band gap significantly decreases, indicating a strong interaction between the BNyen and CO2. DFT computations were employed to explore the mechanism of CO2 reduction to a single carbon product catalyzed by BNyen. Based on the ΔG values, the optimized pathway for this reduction is from CO2 to CH4. Additionally, the potential formation of di-carbon products was considered, and based on the free energy values, CH3CH2OH is identified as the final di-carbon product. The Gibbs free energies for potential CO2 reaction pathways on BNyen were calculated, revealing that CO2 can be reduced to CH4 with a low limiting potential of −0.37 V and to CH3CH2OH with a low limiting potential of −0.57 V, both processes being powered by solar energy. In CO2RR, the competing hydrogen evolution reaction (HER) must be considered. The free energy of HER (ΔG = 0.96 eV) is significantly higher than the ΔG of the rate-determining steps for the mono-carbon product (0.37 eV) and the di-carbon product (0.57 eV) on BNyen. Therefore, BNyen effectively suppresses HER during the CO2RR process. This research can serve as a valuable guide for developing novel types of BNyen as appropriate photocatalysts for CO2 reduction reactions (CO2RR).

Iron mediated n → π* electron transitions and mid-gap states formation in CN under low-temperature secondary calcination enhances photodegradation of organic pollutants

Iron modified carbon nitride (CN) materials have attracted widespread attention from researchers in different application fields. In this paper, single atom iron anchored CN (FeCN) with mid-gap states and n → π* electron transition was synthesized through low temperature secondary calcination. The mid-gap states introduce surface states capable of trapping photogenerated electrons, enabling FeCN to absorb photons with energies lower than its intrinsic optical bandgap. 10%FeCN also exhibits distinct optical absorption above 490 nm derived from the n → π* electron transition, which expand the visible light response range of photocatalysts and enhance electron transport ability. Additionally, the Fe-Nx site enhances the separation and transmission efficiency of photoexcited charges. The prepared 10%FeCN exhibits extremely high photocatalysis and photo-Fenton activity. Mercaptobenzothiazole (MBT) degradation rate of 10%FeCN is 3.47 times higher than CN, achieving a mineralization rate of 86.7% in 100 min. Additionally, the oxytetracycline hydrochloride (OTC) degradation rate of 10%FeCN in photo-Fenton reaction is 11.9 times higher than CN. After five cycles, this catalyst still has good reactivity, indicating its good stability.

Mesostructured Bifunctional ZnBr2/g‐C3N4 Catalysts Towards Efficient Cocatalyst‐Free Cycloaddition of CO2 to Propylene Carbonate

AbstractCatalytic cycloaddition of CO2 with propylene oxide (PO) is a sustainable pathway for the synthesis of propylene carbonate (PC), and the design of efficient heterogeneous catalysts is a hot research topic in both C1 chemistry and functional materials. In this work, graphitic carbon nitride (g‐C3N4) materials were prepared using urea (U) and melamine (M) as precursors through one‐step thermal condensation and then applied as catalyst supports for ZnBr2. As heterogeneous catalysts, the synthesized composites (ZnBr2/g‐C3N4‐MU) exhibited higher activity in the cycloaddition reaction of CO2 to PC than ZnBr2/g‐C3N4‐M and ZnBr2/g‐C3N4‐U. The preparation temperature of ZnBr2/g‐C3N4‐MU could affect the distributions of nitrogen species and acidic strength, which thus determined the final catalytic activity. More importantly, the loading of ZnBr2 not only introduced acidic sites but also enhanced the strength of alkaline sites of g‐C3N4‐MU, enabling ZnBr2/g‐C3N4‐MU materials as acid–base bifunctional catalysts in cycloaddition of CO2 with PO.

Two-dimensional tetragonal carbon nitride semiconductors with fascinating electronic/optical properties and low thermal conductivity

Abstract Exploring two-dimensional (2D) tetragonal carbon nitride materials is significant for unlocking new physical properties beyond those offered by traditional hexagonal lattices. In this work, we propose three theoretically stable 2D carbon nitride monolayers with tetragonal lattices, namely T-C3N, P-C3N, and PH-C5N4. Electronic structure calculations indicate that all three monolayers exhibit semiconducting characteristics, with T-C3N showing interesting flat band features. Additionally, these three carbon nitrides exhibit anisotropic and high carrier mobilities and excellent light absorption capabilities in the visible-light and near-infrared regions. Meanwhile, the calculated thermal conductivity (κp) of PH-C5N4 is 63.9 Wm−1K−1 at room temperature, significantly outperforming T-C3N (12.2 Wm−1K−1) and P-C3N (18.9 Wm−1K−1). Phonon scattering rates and Grüneisen parameters confirm the origin for the relatively high κp in PH-C5N4. Our study proposes three tetragonal carbon nitride structures with novel physical properties, which lays a theoretical foundation for the multifunctional applications of 2D carbon nitride materials.&amp;#xD;

Characterisation Analysis of Sulphur and Phosphorous Doped and Co-doped Graphitic Carbon Nitride (g-C3N4) Materials

Graphitic carbon nitride (g-C3N4) is tailored with doping of different non-metals (Sulphur and Phosphorus). For synthesis through thermal condensation method, the mixtures of urea and dopant with diverse concentrations have been added for preparation of materials. The basic effect of doping and its concentration on the structural morphology and absorption spectra of the samples is investigated in detail. Pure g-C3N4 suffers from high recombination rate of photogenerated electron-hole pairs resulting in low photocatalytic activity. Different techniques like X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transforms infrared (FTIR) spectroscopy, and Photoluminescence spectroscopy (PL) have been used for the characterization. X-ray diffraction studies confirm the formation of the g-C3N4 structure and SEM images reveal crumpled sheets and irregular plate like shapes of the doped graphitic nitride samples. FTIR analysis identify the presence of surface amino (N-H) and water (O-H) groups, cyano terminal group (C≡N), (C≡C), C–N) and (C=N) bonds and breathing mode of the tri-s-triazine units in the samples. PL spectra shows that the sulphur and phosphorus co-doped PSGCN (8 wt.%) sample is better for photocatalytic activity.

A Comprehensive Review of Group-III Nitride Light-Emitting Diodes: From Millimeter to Micro-Nanometer Scales.

This review describes the development history of group-III nitride light-emitting diodes (LEDs) for over 30 years, which has achieved brilliant achievements and changed people's lifestyles. The development process of group-III nitride LEDs is the sum of challenges and solutions constantly encountered with shrinking size. Therefore, this paper uses these challenges and solutions as clues for review. It begins with reviewing the development of group-III nitride materials and substrates. On this basis, some key technological breakthroughs in the development of group-III nitride LEDs are reviewed, mainly including substrate pretreatment and p-type doping in material growth, the proposal of new device structures such as nano-LED and quantum dot (QD) LED, and the improvement in luminous efficiency, from the initial challenge of high-efficiency blue luminescence to current challenge of high-efficiency ultraviolet (UV) and red luminescence. Then, the development of micro-LEDs based on group-III nitride LEDs is reviewed in detail. As a new type of display device, micro-LED has drawn a great deal of attention and has become a research hotspot in the current international display area. Finally, based on micro-LEDs, the development trend of nano-LEDs is proposed, which is greener and energy-saving and is expected to become a new star in the future display field.

Simultaneous Photocatalytic Production of H2 and Acetal from Ethanol with Quantum Efficiency over 73% by Protonated Poly(heptazine imide) under Visible Light.

In this work, protonated poly(heptazine imide) (H-PHI) was obtained by adding acid to the suspension of potassium PHI (K-PHI) in ethanol. It was established that the obtained H-PHI demonstrates very high photocatalytic activity in the reaction of hydrogen formation from ethanol in the presence of Pt nanoparticles under visible light irradiation in comparison with K-PHI. This enhancement can be attributed to improved efficiency of photogenerated charge transfer to the photocatalyst's surface, where redox processes occur. Various factors influencing the system's activity were evaluated. Notably, it was discovered that the conditions of acid introduction into the system can significantly affect the size of Pt (cocatalyst metal) deposition on the H-PHI surface, thereby enhancing the photocatalytic system's stability in producing molecular hydrogen. It was established that the system can operate efficiently in the presence of air without additional components on the photocatalyst surface to block air access. Under optimal conditions, the apparent quantum yield of molecular hydrogen production at 410 nm is around 73%, the highest reported value for carbon nitride materials to date. The addition of acid not only increases the activity of the reduction part of the system but also leads to the formation of a value-added product from ethanol-1,1-diethoxyethane (acetal) with high selectivity.

Incorporation of hydroxyl groups and π-rich electron domains into g-C3N4 framework for boosted sacrificial agent-free photocatalytic H2O2 production

Photocatalytic synthesis of hydrogen peroxide (H2O2) based graphitic carbon nitride (g-C3N4) materials has garnered significant attention due to its green and sustainable attributes. In this study, g-C3N4 nanosheets enriched with π‑rich electron domains and hydroxyl groups were synthesized through the pyrolysis of urea-tartaric acid mixed solution, and subsequently utilized for efficient photocatalytic production of H2O2. The incorporation of π-rich electron domains induced a downward shift in the conduction band edge, which can significantly diminish the Coulombic interactions of singlet Frenkel excitons, thereby facilitating efficient photo-generated charge separation and accelerated charge migration. Simultaneously, the modification with hydroxyl groups in g-C3N4 network enhances water molecule adsorption, reducing side reactions and thereby increasing the efficiency of selective H2O2 generation. The integration of π-rich electron domains with hydroxyl groups in g-C3N4, along with a comprehensive understanding of their underlying mechanisms, provides valuable insights for the rational design and synthesis of highly active energy conversion catalytic materials.

Al1−xScxSbyN1−y: An opportunity for ferroelectric semiconductor field effect transistor

For the in-memory computation architecture, a ferroelectric semiconductor field-effect transistor (FeSFET) incorporates ferroelectric material into the FET channel to realize logic and memory in a single device. The emerging group III nitride material Al1−xScxN provides an excellent platform to explore FeSFET, as this material has significant electric polarization, ferroelectric switching, and high carrier mobility. However, steps need to be taken to reduce the large band gap of ∼5 eV of Al1−xScxN to improve its transport property for in-memory logic applications. By state-of-the-art first principles analysis, here we predict that alloying a relatively small amount (less than ∼5%) of Sb impurities into Al1−xScxN very effectively reduces the band gap while maintaining excellent ferroelectricity. We show that the co-doped Sb and Sc act cooperatively to give a significant band bowing leading to a small band gap of ∼1.76 eV and a large polarization parameter ∼0.87 C/m2, in the quaternary Al1−xScxSbyN1−y compounds. The Sb impurity states become more continuous as a result of interactions with Sc and can be used for impurity-mediated transport. Based on the Landau-Khalatnikov model, the Landau parameters and the corresponding ferroelectric hysteresis loops are obtained for the quaternary compounds. These findings indicate that Al1−xScxSbyN1−y is an excellent candidate as the channel material of FeSFET.

Design and optimization of broadband near-perfect absorber based on transition metal nitrides thin-films for solar energy harvesting

Broadband metamaterial absorbers hold promise for solar energy harvesting, but their complex designs and use of expensive noble metals hinder scalability and thermal stability. Additionally, traditional design methods are time-consuming. We propose a novel approach that combines a genetic algorithm with the transfer matrix method to optimize both material composition and layer structure for large-scale, cost-effective, and thermally stable solar absorbers. This method enables the design of near-perfect absorbers with an average absorptance exceeding 90 % and over 80 % across a broad wavelength range (0.3–2.5 μm) within the key solar spectrum. By optimizing the arrangement of metal and insulator layers using nitride materials (e.g., vanadium nitride), we achieve superior performance compared to traditional metal–insulator and insulator–metal structures. This optimization utilizes resonant absorption and the inherent absorption of metal layers. Our work paves the way for efficient and scalable solar energy harvesting devices.

Influence of the electric field on the electronic structure of flat hexagonal two-dimensional GaN bilayers

Two-dimensional gallium nitride materials have recently garnered significant attention due to their promising optoelectronic properties, chemical stability, and mechanical strength. These attributes make them attractive for various technological applications, particularly optoelectronics, photonics, sensors, and more recently for high-power electronic applications. Our research, using first-principles calculations based on density functional theory (DFT) considering different exchange–correlation functionals, including van der Waals interaction, investigated the electronic properties of a single GaN monolayer and five different stacking configurations of GaN bilayers. The aim is to characterize the electronic properties of 2D-GaN-based materials and explore the impact of external electric fields on the bilayer stacking bandgap. We report the energetically most favorable among the bilayer configurations analyzed. Additionally, we confirmed that it is possible to modulate the energy bandgap both by the type of bilayer stacking and by the effect of the electric field. The ability to tune the energy bandgap (Eg) in 2D-GaN-based materials by adjusting their geometric configuration or applying an external electric field could inspire new applications in various technological fields.

Investigation on the optical properties of group-III nitride materials based on fully-connected neural network

In order to accurately simulate the optical properties of nitride optoelectronic devices, such as the reflection spectrum of distributed Bragg reflectors (DRBs), the optical constant is generally considered an important parameter. In this work, the fully-connected neural network is adopted to predict the real and imaginary parts of ordinary dielectric function (DF) of III-nitrides across the full composition range and wide spectral range. The input parameters include Al-component, Ga-component, In-component, and photon energy. The predicted dielectric constant is basically consistent with the results calculated by the analytical model reported in the literature. Then, the band gaps of 6 eV, 3.4 eV and 0.73 eV for AlN, GaN, and InN were determined by using the Tauc formula. The fitted bowing parameters are 0.94 eV, 4.3 eV, and 1.6 eV for AlGaN, InAlN, and InGaN alloys, respectively. Finally, using the predicted dielectric constant, the calculated reflection spectrum of the DBR structures is in agreement with the experimental results in the literature.

Revealing the effect regularity of cations on electron storage capacity of poly(heptazine imide) in “dark photocatalysis”

As a crystalline carbon nitride material, poly(heptazine imide) (abbreviated as PHI) exhibits higher photoinduced charge separation performance than traditional melon-based carbon nitride. The excellent charge separation is mainly attributed to the fact that the photoinduced electrons can be captured by cations (such as K+ and H+) and further stored in the PHI framework with the presence of sacrificial agents (such as methanol). Due to this special property, the stored electrons can be used for delayed H2O2 or H2 production in the “dark photocatalysis” field. Nevertheless, the effect regularity of cations on the electron storage capacity of PHI is still not clear. In this work, this problem has been preliminarily revealed. The electron storage capacity of a series of PHI materials has been quantified by the H2O2 production test in dark conditions. The result indicates that the electron storage capacity of PHI samples shows a volcano curve with the alkali metal ion content. Based on experimental tests and theoretical simulations, it is concluded that the electron storage capacity of PHI is related to the conductivity of the cation and its binding force for photogenerated electrons.

High-performance pseudo-capacitance supercapacitor with highly mesoporous fluorine doped polymeric carbon nitride nanosheets as electrode material

In this study, graphitic carbon nitride (GCN) material obtained from urea was hydrothermally doped with fluorine atoms (F-doped GCN). The resulting F-doped GCN material was designed as an electrode material for supercapacitors. Characterization of these samples was carried out by XRD, EDS, SEM, nitrogen adsorption and FTIR analyses. EDS and FTIR analyses confirmed the doping of fluorine atoms onto GCN. Nitrogen adsorption analyses supported the formation of a significant mesoporous structure with fluoride doping on GCN. The specific capacitance values of the GCN and F-doped GCN supercapacitors were calculated as 39.75 F/g and 305.72 F/g at a frequency of 0.01 Hz. A significant increase of about 7-fold in capacitance value was obtained by fluorine doping on GCN. Cycling trials of the F-doped GCN supercapacitor for up to 1000 cycles at a current density of 0.4 A/g maintain an efficiency of 86.72 %. For the supercapacitor designed from F-doped GCN material, the maximum energy density and power density were calculated as 4.26 Wh/kg and 1792 Wh/kg, respectively.