Nitrogen Incorporation Research Articles

Strategies for Direct, Transition Metal‐Free Addition of Nitrogen Synthons to Alkenes

AbstractThe incorporation of nitrogen into small molecules is one of the highest‐demanded transformations in modern synthetic chemistry. Alkene difunctionalization and aziridination offer desirable approaches to the incorporation of these amino synthons from feedstock precursors. Although amino groups can be added to alkenes following alkene reaction with an initiation reagent, the most desirable approach involves direct addition of the nitrogen group to the alkene, allowing for a range of possible secondary functionalization outcomes. Although many of these strategies have been accomplished through the use of transition metals, the utility of a transition metal‐free approach is still at the forefront of synthetic chemistry, both in development and demand. This review aims to present a comprehensive review of the history and current state‐of‐the‐art in the transition metal‐free, direct addition of nitrogen to alkenes.

Hydrogen production from pure and crude glycerol photoreforming using platinum supported on TiO2 and N-TiO2

Starting from a commercial TiO2, nitrogen-doped TiO2 (N-TiO2) was synthesized, characterized, platinized, and tested as a photocatalyst for the photoreforming of pure and crude glycerol under UV and visible light for H2 production. The incorporation of nitrogen into the TiO2 structure not only improves its visible light harvest capacity but also increases the catalytic performance, with higher H2 production with respect to platinized bare TiO2.

INFLUENCE OF DOPING WITH CARBON AND NITROGEN ON THE PHOTOACTIVITY OF TiO2 THIN FILMS OBTAINED WITH MePIIID

Titanium dioxide is well known as a photoactive material activated under ultraviolet irradiation. It is either employed as a photocatalyst or it exhibits superhydrophilic behavior after obtaining reduced surface energy under illumination used for self-cleaning or anti-fogging surfaces. For increasing the reactivity of thin films under solar illumination, a reduced band gap is desired. Doping with transition metals or nitrogen has been reported in the literature. However, the incorporation of nitrogen into a growing film is a much more complex process that is presently not completely understood. TiO2 thin layers were produced by metal plasma immersion ion implantation and deposition at room temperature at a pulse voltage of 0–5 kV and a duty cycle of 9 % for an apparently amorphous layer. An auxiliary rf plasma source was employed to increase the growth rate at low gas flow ratios. By adjusting the geometry between the incident ion beam, sputter target and substrate independently of the primary ion energy and species, a controlled deposition of samples was possible. Conventional ion implantation was employed to implant either carbon or nitrogen ions below the surface for bandgap engineering. The resulting thin films were subsequently investigated for optical properties, stoichiometry, structural properties, surface topography and photoactivity.

High-temperature efficient luminescence of dilute-nitride InGaAsN quantum dots with deep electron potential

The temperature dependence of the optical properties of In0.4Ga0.6As0.98N0.02 quantum dots (QDs) was investigated using continuous-wave and time-resolved photoluminescence (PL). Significant increases in the PL peak energy and the PL linewidth were observed at temperatures above 200 K, which reflected the high luminescence efficiency of ground and excited states at high temperatures. The PL decay times of the ground state were almost constant between 200 and 300 K at 200–220 ps, which were significantly longer than that of 38 ps for the In0.4Ga0.6As QDs at 300 K. The temperature independence of the PL decay time represents significant suppression of the thermal escape and the thermal excitation of electrons because the electron ground-state localization energy is much larger than the thermal energy. The PL intensity of the In0.4Ga0.6As0.98N0.02 QDs was seven times stronger than that of the In0.4Ga0.6As QDs at 300 K, and this tendency was maintained up to 400 K with a PL intensity one order of magnitude stronger. These findings demonstrate that lowering the QD conduction band by nitrogen incorporation is an effective approach for achieving strong QD luminescence above room temperature.

Nitrogen-Doped Starbons®: Methodology Development and Carbon Dioxide Capture Capability.

Five nitrogen sources (glycine, β-alanine, urea, melamine and nicotinamide) and three heating methods (thermal, monomodal microwave and multimodal microwave) are used to prepare nitrogen-doped Starbons® derived from starch. The materials are initially produced at 250-300 °C (SNx 300y ), then heated in vacuo to 800 °C to produce nitrogen-doped SNx 800y 's. Melamine gives the highest nitrogen incorporation without destroying the Starbon® pore structure and the microwave heating methods give higher nitrogen incorporations than thermal heating. The carbon dioxide adsorption capacities of the nitrogen-doped Starbons® determined gravimetrically, in many cases exceed those of S300 and S800. The carbon dioxide, nitrogen and methane adsorption isotherms of the most promising materials are measured volumetrically. Most of the nitrogen-doped materials show higher carbon dioxide adsorption capacities than S800, but lower methane and nitrogen adsorption capacities. As a result, the nitrogen-doped Starbons® exhibit significantly enhanced carbon dioxide versus nitrogen and methane versus nitrogen selectivities compared to S800.

Effects of N-functional groups on the electron transfer kinetics of VO2+/VO2+ at carbon: Decoupling morphology from chemical effects using model systems

Carbons and nanocarbons are important electrode materials for vanadium redox flow battery applications, however, the kinetics of vanadium species are often sluggish at these surfaces, thus prompting interest in functionalization strategies to improve performance. Herein, we investigate the effect of N-functionalities on the VO2+/VO2+ redox process at carbon electrodes. We fabricate thin film carbon disk electrodes that are metal-free, possess well-defined geometry and display smooth topography, while featuring different N-site distribution, thus enabling a mechanistic investigation of the intrinsic surface activity towards VO2+/VO2+. Voltammetry and electrochemical impedance spectroscopy show that N-functionalities improve performance, with pyridinic/pyrrolic-N imparting the most significant improvements in charge transfer rates and reversibility, compared to graphitic-N. This was further supported by voltammetry studies on nitrogen-free electrodes modified via aryldiazonium chemistry with molecular pyridyl adlayers. Computational modeling using an electrochemical-chemical mechanism indicates that introduction of surface pyridinic/pyrrolic-N can increase the heterogeneous rate constants by approximately two orders of magnitude relative to those observed at nitrogen-free carbon (k0 = 1.29 × 10−4 vs 9.34 × 10−7 cm/s). Simulations also suggest that these N-functionalities play a role in affecting reaction rates in the chemical step. Our results indicate that nitrogen incorporation via basic functional groups offers an interesting route to the design of advanced carbon electrodes for VRFB devices.

Preparation and properties of heteroatom-doped bacterial cellulose-derived carbonaceous materials

In this study, nitrogen and sulfur heteroatom-doped bacterial cellulose (BC) derived carbon materials have been prepared by a simple, feasible, and environmentally friendly approach that can be easily scaled up for various applications.In the first step, BC was successfully fabricated with chitosan and carrageenan compounds by a layer-by-layer assembly technique without using any template. The resulting composites were then subjected to carbonization to enrich carbon content of the material while incorporation of nitrogen and sulfur heteroatoms into the carbon structure without applying a chemical treatment.A wide variety of BC-derived N- and S-doped carbons were prepared using chitosan and different types of carrageenan precursors. The results showed that the dominant heteroatom on the BC composites was dependent on the last heteroatom precursor used in the layer-by-layer assembly process. The skeleton of the BC composites did not collapse after carbonization and the resulting materials were highly dense and porous having ribbon-like carbon structures. The use of iota-carrageenan as a sulfur precursor with combination of chitosan as a nitrogen precursor resulted in better heteroatom-doped carbons as compared to other carrageenan compounds studied.Synthesized carbons showed great potential as catalyst for hydrothermal conversion of glucose to hydrogen as tested in this study.

N-TiO2/FeMIL-88B- A Promising Photocatalyst for Photoconversion of CO2 into Methanol

The present objective of this work is to find photoactive materials capable of facilitating visible light-driven redox reactions between CO2 and H2O. Our research is primarily focused on the incorporation of nitrogen (N) into the crystal lattice of titanium dioxide (TiO2) and its deposition onto Fe-MIL-88B to improve light absorption properties, minimize recombination of photo-generated electron-hole pairs, and increase CO2 adsorption capacity. The N-TiO2/Fe-MIL-88B composite was successfully prepared and characterized using SEM, XRD, and EDX techniques. The introduction of N-TiO2 into Fe-MIL-88B does not damage the crystal structure of Fe-MIL-88B. Anatase is the only crystalline phase observed from the XRD diffraction pattern. SEM images show that N-TiO2 is well dispersed on the Fe-MIL-88B surface. The results of quantum simulations indicate that TiO2 strongly interacts with Fe-MIL-88B. The binding energy is determined to be -78.2 kcal/mol. The calculated UV-Vis results revealed that the light absorption edge of the TiO2/Fe-MIL-88B was red-shifted in comparison with that of the pure TiO2 (from ca. 500 nm to 550 nm). The red-shifted light absorption of TiO2/FeMIL-88B suggests that the band gap of TiO2/Fe-MIL-88B is narrower compared to that of the pristine TiO2, indicating the better light utilization ability of the TiO2/Fe-MIL-88B. Results from high-performance liquid chromatography show that N-TiO2 has the capability to convert CO2, but at a significantly low rate. The methanol formation is distinctly observed only over the N-TiO2/Fe-MIL-88B catalyst. The CO2 conversion efficiency, estimated using gas chromatography, is calculated to be 11.94%.

Oxidation behavior of novel ultra-high temperature hafnium-zirconium carbonitrides: Effect of nitrogen and metal ratios

In this work, the effect of nitrogen and the Hf/Zr ratio on the oxidation resistance of hafnium-zirconium carbides and carbonitrides have been investigated. According to thermogravimetric investigations, carbonitride samples containing 50 and 20 at% Zr exhibit the smallest weight gains of 15.5 and 11.5 %, respectively. The isothermal exposure of the samples at 1200 °C revealed that the incorporation of nitrogen into the lattice of hafnium-zirconium carbides results in a decrease in the oxidation rate by 2–3.5 times, depending on the Zr content. The hafnium-zirconium carbonitride (Hf0.8Zr0.2)C0.5N0.3 has shown to possess the highest level of oxidation resistance.

Nitrogen Radiofrequency Plasma Treatment of Graphene

AbstractThe incorporation of nitrogen (N) atoms into a graphitic network such as graphene (Gr) remains a major challenge. However, even if the insertion mechanisms are not yet fully understood, it is certain that the modification of the electrical properties of Gr is possible according to the configuration adopted. Several simulations work, notably using DFT, have shown that the incorporation of N in Gr can induce an increase in the electrical conductivity and N acts as an electron donor; this increase is linked to the amount of N, the sp2/sp3 carbon configuration, and the nature of C−N bonding. Nitrogen radiofrequency (RF) plasma has been used to incorporate N into Gr materials. The RF plasma method shows the possibility to incorporate N‐graphitic nitrogen into Gr after a pre‐treatment with nitric acid. X‐ray photoelectron spectroscopy and Raman spectrometry were used to quantify the functionalized groups. The modifications of the graphene surface chemistry along the amount of N inside the Gr change the chemical environment of N. This method, enabling the incorporation of N inside Gr matrix, opens up a route to a broad range of applications.

Two-Dimensional Covalent Organic Frameworks as Tailor-Made Scaffolds for Water Harvesting.

Developing materials to harvest water from the air is of great importance to alleviate the water shortage for people living in arid regions, where the annual average relative humidity (RH) is lower than 0.4. In this work, we report a general nitrogen atom incorporation strategy to prepare high-performance covalent organic frameworks (COFs) for water harvesting from the air in arid areas. A series of COFs, namely COF-W1, COF-W2, and COF-W3 were developed for this purpose. Different contents of nitrogen were embedded into COFs by incorporating pyridine units into the building blocks. With the increasing content of nitrogen from COF-W1 to COF-W3, the inflection points of their water isotherms shift distinctly from RH values from 0.65 to 0.25. Significantly, COF-W3 exhibits the lowest inflection point at a low RH value of 0.25 and reaches a high uptake capacity of 0.28 g g-1 at 25 °C with a low hysteresis loop. Moreover, the gram-scale COF-W3 retains its high performance, which renders it more attractive in water harvesting. This work demonstrates the feasibility of this nitrogen incorporation strategy to acquire high-performance COFs as water harvesters in the future.

Synergistic enhancement of photocatalytic and antimicrobial efficacy of nitrogen and erbium co-doped ZnO nanoparticles

Using the chemical co-precipitation approach, a series of nitrogen (N) and erbium (Er) co-doped ZnO nanoparticles (NPs) was effectively synthesized to enhance the photocatalytic and antibacterial activities. Several characterization techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-vis, and photoluminescence (PL) spectroscopy, were carried out to validate the evaluated photocatalytic and antibacterial activities. XRD analysis confirms the pure wurtzite ZnO phase without the presence of any secondary phase. XPS analysis confirms the successful incorporation of nitrogen and erbium into the ZnO matrix. The optical bandgap of ZnO calculated from UV-vis spectroscopy shows a redshift after Er–N co-doping, with the lowest bandgap of 3.215 eV calculated for Zn0.97Er0.03N0.01O0.99 NPs. SEM images demonstrate the formation of nanorods after N–Er co-doping, followed by gradually increased rod diameter and length after N–Er co-doping. Moreover, the photocatalytic activities of ZnO samples were measured by their ability to facilitate the photodegradation of Rhodamine B under UV irradiation. ZnO with 1 mol% N doping exhibits 88% photodegradation of RhB under UV light within 360 min, and the photodegradation and antibacterial activity are greatly improved with Er co-doping. In fact, 3 mol% Er-1 mol% N doped ZnO NPs demonstrate the highest photocatalytic activity, with approximately 96% degradation after 360 min, as well as superior antibacterial activity against Staphylococcus aureus (Gram-positive bacteria) and Pseudomonas aeruginosa (Gram-negative bacteria) with the highest zone of inhibition (ZOI) of 16 nm, due to nanorod formation, increased reactive oxygen species (ROS), and decreased electron–hole recombination, as validated by SEM, XPS, and PL spectroscopy.

Nitrogen incorporation endows copper notable activity for the selective reduction of nitroarenes

The selective reduction of nitroarenes to corresponding anilines using hydrazine hydrate as hydrogen carrier still focus on the employment of Fe and Co based materials as catalysts, while earth abundant and environmental friendly Cu based catalysts are rarely reported in this field. Herein, a cost-effective N modified Cu decorated on carbon nanotubes catalyst CuNCNT was designed and demonstrated comparable or better performance than many reported materials. It showed that N doping notably switched Cu from inactive to highly active, and the atomically dispersed Cu species were proposed to be the critical active sites. Moreover, the in-situ generated active [H] species derived from hydrazine decomposition was considered to be responsible for the reduction.

Unlocking efficiency in oxygen reduction reaction: Synergistic edge dopants of nitrogen and boron in carbon nano onions

Oxygen reduction reaction (ORR) is a crucial process for energy conversion and storage devices. Despite platinum (Pt) being the state-of-the-art material for ORR, the limited performance of Pt-based catalyst, Pt scarcity, and vulnerability of global supply chains for critical minerals, have made it imperative to develop alternative electrocatalysts that either contain no precious metals at all or require only a very low loading of these valuable resources. In this study, we demonstrate that the incorporation of co-dopants, nitrogen (N) and boron (B), with a dissimilar electronegativity is a promising approach to develop metal-free electrocatalysts for ORR. We discovered that the interaction between N and B plays a vital role in both (i) incorporating the dopants in high-curvature carbon nano-onions (CNOs) and (ii) promoting ORR performance. Tuning the annealing temperature was crucial to achieve a desirable N-B chemical configuration and synergistic effects of N and B on ORR catalysis. Our investigation revealed that N,B-doped CNOs prepared at 700 °C exhibit the best ORR performance in 0.1 M KOH with a dominant 4-electron pathway and excellent durability. Based on X-ray photoelectron spectroscopy (XPS), Raman analysis, and high-resolution scanning transmission electron microscopy (HR-STEM), we conclude that abundant N and B sites, especially N-C-B (isolated) sites, at the edges in conjunction with high surface activity of CNOs are responsible for such outstanding performances. This study provide insights into the design of metal-free catalysts for efficient ORR catalysis, and the importance of alternative electrocatalysts in the current global supply chain disrutipn scenario.

Nitrogen modification enhances conductivity and reactivity of sulfidated zero-valent iron: Mechanism and Cr(VI) removal

The incorporation of electronegative elemental nitrogen into zero-valent iron (ZVI)/sulfidated zero-valent iron (S-ZVI) has emerged as an outstanding and promising way to improve decontamination performance. However, the impact of nitrogen modification on the electrical structure of ZVI/S-ZVI remains unclear. Herein, nitrogen-modified sulfidated zero-valent iron (S-N-ZVI) was successfully obtained utilizing cheap and accessible ammonium chloride as the nitrogen source. Raman spectra, FTIR, and density functional theory (DFT) calculations demonstrated that NH3 acts as the dominant nitrogen species. According to the projected density of states and charge-density difference calculations, N is successfully bound to Fe, resulting in a redistribution of surface charge and an increase in electron density of S-N-ZVI, which is reflected in the improved conductivity of S-N-ZVI. Compared with S-ZVI, S-N-ZVI demonstrates better performance in terms of Cr(VI) removal kinetics (kobs improved by 2.075 folds), resistance to air aging, reusability and ability to preserve FeSX stability. This study highlights that the electronic structure significantly impacts the physicochemical properties of S-ZVI and reveals the mechanism of nitrogen modification on the electronic structure of S-ZVI.

Multiple transition temperature enhancement in superconducting TiNbMoTaW high entropy alloy films through tailored N incorporation

We report about the influence of nitrogen incorporation on the superconducting transition temperature TC of TiNbMoTaW high entropy alloy films deposited using high power impulse magnetron sputtering. By measuring the temperature dependence of resistivity of (TiNbMoTaW)Nx nitrides, we observe a significant increase of TC, from 0.62 K for x = 0 up to 5.02 K for x = 0.74. With further increase of x, TC is decreasing and reaches 1.08 K for x = 0.97. The eightfold TC enhancement seems to be associated with the incorporation of light N atoms into the face-centered cubic lattice and with the x dependent enhancement of the electron-phonon interaction, which may be related to the high configuration entropy in high entropy alloys. Measurements in magnetic field show that the upper critical fields Bc2 of (TiNbMoTaW)Nx with x > 0.15 provide Bc2/TC > 2 T/K ratios, which are above the weak-coupling pair breaking limit. Additional heat capacity and point contact spectroscopy measurements show that the superconductivity in the ∼1 μm thick films is bulk in nature, consistent with conventional weak-coupling phonon mediated superconductivity. The proposed strategy of nitrogen incorporation into high entropy alloys may pave a pathway towards tailoring their superconducting properties, especially their TC.

The Adsorption of 2,4-Dichlorobenzoic Acid on Carbon Nanofibers Produced by Catalytic Pyrolysis of Trichloroethylene and Acetonitrile

In this study, carbon nanofibers were synthesized by the catalytic pyrolysis of trichloroethylene (CNF-Cl) and its mixture with acetonitrile (CNF-Cl-N). The addition of acetonitrile resulted in the incorporation of nitrogen in the CNF (0.33 at%), the removal of chlorine, an increase in oxygen-containing functional groups on the surface (from 1.6 to 3.6 at%), and an increase in the volume of mesopores (from 0.35 to 0.41 cm3·g−1) and macropores (from 0.115 to 0.393 cm3·g−1). The study of 2,4-DCBA adsorption on both CNFs revealed that the adsorption capacity showed dependence with a maximum on the 2,4-DCBA concentration in the solution, which was attributed to the electrostatic interactions of adsorbate with adsorbent at various pHs. The adsorption forces were effective over distances greater than the size of the 2,4-DCBA molecule, indicating volume pore filling. The maximum adsorption capacity occurred at 0.7–1.2 mM and a pH of 3.4 ± 0.1. CNF-Cl-N exhibited lower 2,4-DCBA adsorption than CNF-Cl-N due to its lower specific surface area, lower micropore volume, and higher concentration of oxygen-containing groups on the surface. However, these differences were not significant, suggesting that CNFs produced from both chlorine-containing wastes and their mixtures with nitrogen-containing compounds can be effectively used for water treatment to remove 2,4-DCBA.

The effects of high temperature thermal treatments on β-Ga2O3 films grown on c-sapphire by low-pressure CVD

As a simple and effective method for improving the crystalline quality of epitaxial Ga2O3 film, post-thermal treatment has been identified as a competitive process involving crystal reconstruction accompanied by defect formation. In this study, β-Ga2O3 films grown on a c-sapphire substrate using low-pressure chemical vapor deposition were subjected to thermal treatment at 1000 °C in air for various duration to investigate the effects of treatment time on the films. The full width at half maximum (FWHM) of x-ray rocking curves initially decreased from 1.62° to 0.98° with increasing treatment time up to 5 h, indicating improved crystallinity. This improvement is likely a result of the reduced angle between Ga2O3 grains and the reconstructed Ga2O3 lattice, oriented towards the (−201) plane due to the thermal treatment, as observed in the transmission electron microscope and electron back-scattering diffraction results. However, under 7 h of treatment, the crystallinity of Ga2O3 degraded, as evidenced by an increased FWHM, as well as by x-ray photoelectron spectroscopy, photoluminescence, and time-of-flight secondary ion mass spectrometry results. This degradation can be attributed to the presence of massive oxygen vacancies and the substitutional incorporation of nitrogen into oxygen sites (NO), resulting in defects.

Improving Nitrogen Retention in Algal Biochar Pyrolysis by Co‐Pyrolysis with Glucose

AbstractAlgal biomass is a promising pyrolysis feedstock, however, large amounts of nitrogen‐containing compounds (NH3, HCN,…) are emitted during its conversion. These emissions can be decreased by incorporating nitrogen in the biochar's carbon matrix via co‐pyrolysis. This study investigates whether adding glucose (GL) to the microalgae, Arthrospira sp. (SP), increases the nitrogen fixation in the solid biochar. Moreover, scalable (co‐) pyrolysis experiments are linked with micro‐scale pyrolysis. Using hyphenated pyrolysis (Py–GC–MS, TG‐IR) and characterization (CHNS, XPS, and Raman) techniques the phenomena associated with the incorporation of nitrogen in the biochars are unraveled. Co‐pyrolyzing SP and GL increased biochar yields and nitrogen retention, which is attributed to Maillard reactions occurring in the initial pyrolysis stages. In conclusion, this study provides evidence that co‐pyrolysis of microalgae and reducing sugars is a more sustainable strategy to produce algae‐based biochar.

Coconut waste to green nanomaterial: Large scale synthesis of N-doped graphene nano sheets

In this paper, a breakthrough was achieved in large-scale production of N-doped Graphene Nano Sheets (N-GNS) using coconut fruits. The main objectives were to produce N-GNS on a large scale and assess its electrical conductivity. The process involved two key steps: first, producing GNS from coconut fruits through pyrolysis, and then generating N-GNS by doping with nitrogen using ammonia solution at room temperature. Various analytical techniques were used to characterize the produced N-GNS, including X-ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Raman spectroscopy, and electrochemical cyclic voltammetry and electrochemical impedance spectroscopy. The XRD data indicated that the C (002) peak of N-GNS shifted to a higher 2θ value (2θ = 24.72°) compared to GNS (2θ = 23.86°), suggesting an incorporation of nitrogen into carbon structure in N-GNS. This was further supported by XPS data, which identified N-pyridine (BE = 402.0 eV) and C-N (BE = 286.8 eV) in N-GNS. TEM images showed that N-GNS had a flat surface, and the distance between graphene layers slightly expanded (0.36 nm) compared to graphene layers (0.34 nm). SEM images and EDX data validated the morphology, resembling honeycomb lattices, with a significant content of N atoms. Raman data successfully identified the D-band and G-band in N-GNS, further validating its production. Most importantly, N-GNS exhibited electrical conductivity, making it a promising candidate for conductive and supporting materials in various applications. The significance of this research extends beyond N-GNS production, opening up new avenues for the sustainable synthesis of valuable nanomaterials from coconut fruit waste, contributing to both graphene technology and environmental conservation.