Ultrahigh Nitrogen Content Research Articles

Revealing the Hygroscopic Behavior of Ultrahigh Nitrogen Content Cyclo‐Pentazolate Salts

AbstractThree representative cyclo‐pentazolate salts including N2H5+N5−, NH3OH+N5− and NH4+N5−, are highly favored for their ultrahigh nitrogen content (80–96%). However, their ambiguous nature has severely restricted the application exploration. Herein, the relationships between humidity and moisture content of salt were established by quantitative analysis. Among the three salts, the hygroscopic ability has the following order: NH3OH+N5−>NH4+N5−>N2H5+N5−. Especially in the range of 40% RH −60% RH, the NH3OH+N5− has a high sensitivity to water, and the absorbed moisture content can be as high as 20.8% at 60% RH. When the relative humidity exceeds 60% RH, the hygroscopic rate of NH3OH+N5− rises sharply, at 80% RH, NH3OH+N5− will absorb excess moisture and turns into liquid form. After treating NH3OH+N5− at 40% RH, the very sensitive friction sensitivity (FS) and impact sensitivity (IS) of dried NH3OH+N5− (FS=20 N, IS=2 J) will change into insensitive salt (FS>360 N, IS>40 J). The higher moisture content in NH3OH+N5−, the lower the thermal stability, its thermal decomposition temperature (103.22°C) is 3.24°C lower than that of dry salt (106.46°C) at 75% RH (moisture content is 30.2%). The other two salts N2H5+N5− and NH4+N5− have the similar properties. Molecular dynamics simulation was further applied to explain the strong hygroscopicity of salts.

Ultrahigh nitrogen-doped carbon derived from g-C3N4 assisted by citric acid for superior potassium-ion storage

Nitrogen-doped carbon is regarded as a promising anode for potassium ion batteries (PIBs) because nitrogen atoms can regulate the structures of carbon and generate abundant active sites. How to improve the nitrogen content in carbon through simple and effective methods remains to be further addressed. In this paper, a carbon material (60NC) with ultrahigh nitrogen content (16 %) was prepared from graphite phase carbon nitride (g-C3N4) by a convenient freeze-drying and high-temperature pyrolysis method, assisted by citric acid. When used as an anode for PIBs, 60NC exhibited a superior reversible capacity of 318.1 mAh g−1 after 200 cycles at 0.1 A g−1. Even at the high current density of 1A g−1, 60NC maintained a specific capacity of 261.8 mAh g−1 after 1000 cycles. The excellent electrochemical performance of 60NC mainly stems from its abundant K+ storage active sites caused by nitrogen doping, large layer spacing, and hierarchical porous structure.

Activating peroxymonosulfate by high nitrogen-doped biochar from lotus pollen for efficient degradation of organic pollutants from water: Performance, kinetics and mechanism investigation

Nitrogen-doped biochars are promising metal-free catalysts for peroxymonosulafe (PMS) activation due to their low-cost, high chemical stability and metal-free leaching. However, the nitrogen content in the biochar is usually low with unsatisfactory performance, and the in-depth analysis on the kinetic of pollutant degradation is still insufficient. Herein, high nitrogen doped biochars were prepared by one-step pyrolysis of lotus pollen (LP) and melamine, which were used to trigger PMS for degrading organic pollutants in water. The optimized nitrogen-doped LP biochar (N-LPC-5) possessed ultrahigh nitrogen content (up to 15.75 at%) and abundant oxygen-containing functional groups, which exhibited the optimal performance in activating PMS to degrade reactive black 5, atrazine, ketoprofen and p-nitrophenol. The removal efficiency for all the organic pollutants in the N-LPC-5/PMS system can reach above 90 % in 20 min, and the degradation performance was outstanding in a wide pH range from 2.0 to 10.5. The pollutant degradation followed a two-stage process including a fast stage of initial oxidation and a slow stage. An appropriate mathematic kinetic model was proposed to describe the two-stage reaction. Fitting the experimental data with the proposed kinetic model, the initial removal rate and the maximal oxidation capacity can be obtained accordingly, and the correlation coefficients were very close to 1.0, indicative of the excellent fitness of the proposed model. In addition, the catalytic mechanisms such as the reactive oxygen species, electron-transfer pathway and active sites were also investigated by various techniques. The present study highlights the tremendous potential of N-biochar for wastewater remediation, and helps to understand the dynamic kinetics and catalytic mechanism of metal-free carbon activating PMS.

Direct synthesis of highly crumpled nitrogen-rich porous carbon nanosheets with a mesopore-dominant for high performance supercapacitors

Direct synthesis of porous carbon nanosheets without adding any chemical activators or templates remains a great challenge. In this work, we present a novel and simple method to synthesize highly crumpled nitrogen-rich porous carbon nanosheets (HCNPCNS) by one-step procedure based on the direct carbonization of polyethylene and melamine. HCNPCNS consist of interconnected crumpled porous carbon nanosheets with a nanoscale thickness, an ultrahigh nitrogen content (10.3 at.%) and a mesopore-dominant, which thus ensure much more available surface area. As a result, the unique structures of HCNPCNS exhibit a high specific capacitance of 257.2 F g−1 in 6 M KOH and 265 F g−1 in 1 M H2SO4, high rate capability both in 6 M KOH and 1 M H2SO4, and long cycling stability of 96.7 % in 6 M KOH and 100 % in 1 M H2SO4 when act as supercapacitor electrodes. Moreover, the HCNPCNS//HCNPCNS based supercapacitor in ionic liquid can deliver an excellent power density of 175 kW kg−1 and an energy density of 58.8 W h kg−1. This strategy opens up a new avenue towards preparing porous carbon nanosheets without complicated procedure and particular chemical activators or templates for high performance supercapacitors.

Rational regulation of 3D N-doped carbon macro-architectures toward low-temperature plasma catalysis: The roles of nitrogen content and hierarchical porous structure

The application of low-temperature plasma technology with optimized catalysts in water treatment has shown a good application prospect. However, the relationships between catalytic performance and composition (N atom-doping) and structure (hierarchical porous) of catalysts is still unclear. Here, 3D N-doped carbon macro-architectures is designed by thermolysis of energetic Zn-MOF, where triazole ligand with ultra-high nitrogen content provided the possibility for effective nitrogen doping and creation of hierarchical porous structure. In the DBD system, a series of energetic MOF-derived carbon (EMC-x) catalysts with different pyrolysis temperatures (from 700 to 1000 °C) were prepared, and the composition/structure-effective relationship was investigated in detail. Degradation mechanisms and pathways were analyzed by bursting experiments, quantitative detection of H2O2 and O3, three-dimensional excitation-emission matrix spectroscopy (3D-EEM), LC-MS. The results confirmed that EMC-10 with high nitrogen content and hierarchical porous structure has a wide range of applications in synergistic plasma removal of TTCH from water bodies.

Imidazole linker‐induced covalent triazine framework–ZIF hybrids for confined hollow carbon super‐heterostructures toward a long‐life supercapacitor

AbstractCarbon super‐heterostructures with high nitrogen contents from the covalent hybrid precursors of covalent triazine frameworks (CTFs) and zeolitic imidazolic frameworks (ZIFs) are scarcely explored because of CTF's ordered structure and toxic superacid that dissolves or destabilizes the metal nodes. To solve this problem, herein, we report a straightforward two‐step pathway for the covalent hybridization of disordered CTF (d–CTF)–ZIF composites via preincorporation of an imidazole (IM) linker into ordered CTFs, followed by the imidazole‐site‐specific covalent growth of ZIFs. Direct carbonization of these synthesized d–CTF−IM−ZIF hybrids results in unique hollow carbon super‐heterostructures with ultrahigh nitrogen content (>18.6%), high specific surface area (1663 m2 g−1), and beneficial trace metal (Co/Zn NPs) contents for promoting the redox pseudocapacitance. As proof of concept, the obtained carbon super‐heterostructure (Co–Zn–NCSNH–800) is used as a positive electrode in an asymmetric supercapacitor, demonstrating a remarkable energy density of 61 Wh kg−1 and extraordinary cyclic stability of 97% retention after 30,000 cycles at the cell level. Our presynthetic modifications of CTF and their covalent hybridization with ZIF crystals pave the way toward new design strategies for synthesizing functional porous carbon materials for promising energy applications.

Constructing quinazolinone-anchored electron-rich covalent organic frameworks by photocatalytic reductive cyclization for idealizing iodine capture

Constructing ideal adsorbent for the capture of radioactive iodine often requires both high adsorption capacity and fast adsorption kinetics. However, this remains a challenging issue. Herein, we present an effective method to idealize iodine capture with both ultrahigh adsorption capacity and fast adsorption rate through the construction of quinazolinone-anchored covalent organic frameworks (COFs). Post-synthesis modification was employed to functionalize two vinyl free-standing COFs with quinazolinone units through in-situ photocatalytic reductive cyclization between vinyl and 2-aminobenzamide units. The developed material, ECUT-COF-13, exhibits not only I2 uptake capacity as high as 10.81 g g−1, exceeding all established adsorbents for such use, but also very fast adsorption rate of 1.4 gh−1, surpassing all previously reported two-dimensional COFs. The outstanding I2 capture performance mainly results from an electron-rich mechanism, since anchoring quinazolinone units in COFs will lead to enhanced π-conjugated net and ultrahigh nitrogen content. The results demonstrate not only a new avenue for functionalizing COFs, but also a general electron-rich strategy for COFs.

Nitrogen-Doped Hollow Carbon Spheres Based on Schiff Base Reaction as an Anode Material for High-Performance Lithium and Sodium Ion Batteries.

Nitrogen-doped carbon has great potential in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), considering N-doping can not only improve the surface wettability of carbon materials, but also accelerate charge transfer by generating additional defects. However, designing carbon materials with a high nitrogen content and uniform distribution using conventional doping methods remains a challenge. In this study, a hollow carbon sphere with an ultrahigh nitrogen content of 9.58 wt % was successfully fabricated by rationally designing Schiff base chemistry (PTA-NHCS-700). Stable hierarchical pore structures, moderate defects, and large specific surface areas were formed during the carbonization process. Excellent electrochemical performance was observed in LIBs (204.2 mAh g-1 after 7000 cycles at 5 A g-1 ) and SIBs (154.2 mAh g-1 after 10000 cycles at 5 A g-1 ). This study not only promotes the development of efficient carbon anode materials for LIBs and SIBs, but also provides a novel idea for the doping of heteroatoms with special chemical structures.

A hybrid of tetrazolium and pentazolate: An energetic salt with ultrahigh nitrogen content and energy

As a full nitrogen energetic anion, pentazolate (cyclo-N5ˉ) holds great promise in the fields of propellants and explosives. Nowadays, nonmetallic pentazolate salts have received extensive attention as excellent nitrogen-rich energetic materials for their high enthalpies of formation, good oxygen balance, and eco-friendly decomposition products. In this study, a 1,4,5-triaminotetrazolium-based pentazolate salt (TATe+N5ˉ, 8) with a nitrogen content of up to 90.30% was designed and synthesized. Its crystal structure indicates that a large number of hydrogen bonds form a hydrogen-bonded network, and the crystal has a mixed stacking pattern. TATe+N5ˉ, which has a relatively high density (1.64 ​g·cm−3), high heat of formation (861.9 ​kJ·mol−1), and excellent detonation performances (detonation velocity: 9487 ​m·s−1, detonation pressure: 32.5 ​GPa), provides new insights into the stability of ultrahigh-nitrogen compounds.

A Solvent-Polarity-Induced Interface Self-Assembly Strategy towards Mesoporous Triazine-Based Carbon Materials.

Triazine-based materials with porous structure have recently received numerous attentions as a fascinating new class because of their superior potential for various applications. However, it is still a formidable challenge to obtain triazine-based materials with precise adjustable meso-scaled pore sizes and controllable pore structures by reported synthesis approaches. Herein, we develop a solvent polarity induced interface self-assembly strategy to construct mesoporous triazine-based carbon materials. In this method, we employ a mixed solvent system within a suitable range of polarity (0.223≤Lippert-Mataga parameter (Δf) ≤0.295) to induce valid self-assembly of skeleton precursor and surfactant. The as-prepared mesoporous triazine-based carbon materials possess uniform tunable pore sizes (8.2-14.0 nm), high surface areas and ultrahigh nitrogen content (up to 18 %). Owing to these intriguing advantages, the fabricated mesoporous triazine-based carbon materials as functionalized porous solid absorbents exhibit predominant CO2 adsorption performance and exceptional selectivity for the capture of CO2 over N2 .

A Solvent‐Polarity‐Induced Interface Self‐Assembly Strategy towards Mesoporous Triazine‐Based Carbon Materials

AbstractTriazine‐based materials with porous structure have recently received numerous attentions as a fascinating new class because of their superior potential for various applications. However, it is still a formidable challenge to obtain triazine‐based materials with precise adjustable meso‐scaled pore sizes and controllable pore structures by reported synthesis approaches. Herein, we develop a solvent polarity induced interface self‐assembly strategy to construct mesoporous triazine‐based carbon materials. In this method, we employ a mixed solvent system within a suitable range of polarity (0.223≤Lippert–Mataga parameter (Δf) ≤0.295) to induce valid self‐assembly of skeleton precursor and surfactant. The as‐prepared mesoporous triazine‐based carbon materials possess uniform tunable pore sizes (8.2–14.0 nm), high surface areas and ultrahigh nitrogen content (up to 18 %). Owing to these intriguing advantages, the fabricated mesoporous triazine‐based carbon materials as functionalized porous solid absorbents exhibit predominant CO2 adsorption performance and exceptional selectivity for the capture of CO2 over N2.

Construction and preparation of nitrogen-doped porous carbon material based on waste biomass for lithium-ion batteries

Biomass derived carbon materials have been widely studied as electrodes in energy storage devices due to their renewable nature, low-cost and tunable physical/chemical properties. However, the influences of different treatments for biomass derived carbon materials are still lack of in-depth discussion. In this work, we investigate the effects of the treatment for biomass on the structure and composition of the resulted carbon materials. Especially, the optimal N-doped porous carbon (NPCCS), which was fabricated by H2SO4-assisted hydrothermal treatment and subsequent pyrolysis process using corn silk as raw material, shows a unique interconnected layered nanostructure with ultra-high nitrogen content (18.79 at%). As a result, the NPCCS electrode displays excellent cycling stability and outstanding rate performance in lithium-ion half-cell test and shows high first reversible specific capacity of 523.6 mAh g−1 in full-cell test. This work provides some guidance for preparing biomass derived carbon materials with superior electrochemical performance for the applications in advanced energy storage devices.

Monodisperse Ultrahigh Nitrogen-Containing Mesoporous Carbon Nanospheres from Melamine-Formaldehyde Resin.

An aqueous emulsion polymerization self-assembly approach is demonstrated for the first time to synthesize ultrahigh nitrogen containing mesoporous polymer nanospheres, using melamine-formaldehyde resin oligomers as precursors. In the synthesis, change from alkaline to acidic conditions is critical for the formation of monodisperse mesostructured polymer nanospheres. Owing to unique structure of triazine stabilized in the covalent polymeric networks during the pyrolysis process, the derived mesoporous carbon nanospheres possess an ultrahigh nitrogen content (up to 15.6 wt%) even after pyrolysis at 800°C, which is the highest nitrogen content among mesoporous carbon nanospheres. Furthermore, these monodisperse mesoporous carbon nanospheres possess a high surface area (≈883 m2 g-1 ) and large pore size (≈8.1nm). As an anode for sodium-ion batteries, the ultrahigh nitrogen-containing mesoporous carbon nanospheres exhibit superior rate capability (117 mAh g-1 at a high current density of 3 A g-1 ) and high reversible capacity (373 mAh g-1 at 0.06 A g-1 ), indicating a promising material for energy storage.

Vitamin B9 derived nitrogen-doped graphene for metal-free aerobic oxidation of biomass-derived chemicals

A superior carbocatalyst ultrahigh N-doped graphene (NG) was prepared by a novel self-sacrificial templating method of one-step annealing vitamin B9. The NG catalyst with pyrolysis temperature of 800 °C (abbreviated VB9-NG-800) has an ultrahigh nitrogen content of 13.5 wt% and demonstrated the highest activity for the oxidation of bio-based alcohols and terpenes with molecular oxygen without any additives. Systematic characterizations and quantum-chemical calculations further manifested that high contents of graphitic N and pyridinic N species in VB9-NG-800 promoted the generation of O2− active species from molecular oxygen effortlessly, resulting in excellent catalytic performance for aerobic oxidation.

Coupling hollow Fe3O4 nanoparticles with oxygen vacancy on mesoporous carbon as a high-efficiency ORR electrocatalyst for Zn-air battery

Designing a low-cost, high-efficiency and robust doped-carbon-based oxygen reduction reaction electrocatalyst for large-scale implementations of fuel cells is highly desirable but challenging. In this work, we report a new type of hollow Fe3O4 with oxygen vacancy incorporating on mesoporous carbon prepared by pyrolyzing mesoporous carbon enriched with oxygen-containing functional groups, in combination with ferric acetylacetonate. The catalysts possess high specific surface area with predominantly mesoporous architecture and ultrahigh nitrogen content (up to 7.47 wt%). Benefiting from the integration of abundant active nitrogen and Fe-Nx species, and synergistic effect between Fe3O4 nanoparticles cooperated with oxygen vacancy and N-doped carbon, the half-wave potential of the preparing hybrid catalyst is 30 mV more positive than that of the commercial Pt/C catalyst in alkaline medium, and exhibits a high selectivity (4 e− process), and outstanding long-term stability. More importantly, the C-FePPDA-900 catalyst displays a high power density (106 mW cm−2) and specific capacity of 724 mAh gzn−1 when it is used as an air cathode catalyst in a specifically assembling Zn-air cell, superior to those of most reported catalysts.

Highly nitrogen-doped porous carbon transformed from graphitic carbon nitride for efficient metal-free catalysis

Nitrogen-doped carbon materials are proposed as promising metal-free catalysts for persulfate-mediated catalytic oxidation process, yet the nitrogen content in the final carbon products is typically low. Moreover, controversies remain in the unambiguous identification of active sites in nitrogen-doped carbons for persulfate activation. Here we report the facile synthesis of nitrogen-doped carbon material via one-step pyrolysis of urea and D-mannitol, which simultaneously combine ultrahigh nitrogen content (up to 33.75 at%) with apparent porous structure via transformation from graphitic carbon nitride. With this strategy, the highly nitrogen-doped porous carbon (NC1.0) exhibits excellent catalytic activity toward peroxymonosulfate (PMS) activation for oxidation of organic pollutants. Both experiments and density functional theory (DFT) calculations, for the first time, revealed that the electron-rich graphitic N and electron-deficient carbon atom adjacent to graphitic N in NC1.0 served as active sites for PMS reduction and oxidation toward the generation of hydroxyl radical (OH) and singlet oxygen (1O2), respectively, in which PMS oxidation was the main reaction in the course of PMS activation rendering 1O2 the dominant reactive oxygen species (ROS) in the NC1.0/PMS system. More importantly, NC1.0 presents robust stability in PMS activation, superior to most reported nitrogen-doped carbon-based catalysts, offering great promise for practical environmental remediation.

Ultra-high nitrogen content biomass carbon supercapacitors and nitrogen forms analysis

Doping of heteroatoms is an effective way to improve the specific capacitance of carbon-based supercapacitors. In this paper, we prepared an active biomass carbon electrode with a considerable nitrogen content of 10.82%. In the N-doped biomass carbon materials, pyridine nitrogen and pyrrole nitrogen were the main forms of nitrogen, and the presence of sp3 hybrid nitrogen greatly enhanced the specific capacitance. Among the precursors of biomass in this study, fungal hypha (FH) enabled the best electrochemical performance of carbon electrode with specific capacitances of up to 279 F/g and 190 F/g at a high current density of 1 A/g and 20 A/g, respectively. In addition, the sample possessed an excellent anti-radiation capability, with the specific capacity of 227 F/g at 1 A/g after irradiated by γ-ray (50 kGy). This universal and cost-friendly method will expand the specific surface area of biomass materials and augment the amount of nitrogen in biomass carbon materials.

Nitrogen-doped hierarchical porous carbon with ultrathin graphitic framework for superior lithium storage

The fabrication of nanocarbons possessing ultrathin graphitic structure and ultrahigh nitrogen doping simultaneously remains challenging so far. Herein, we develop a novel and versatile strategy to prepare ultrahigh nitrogen-doped hierarchical porous carbon with ultrathin graphitic framework (NHPCs), through the Schiff-base reaction of melamine and terephthalaldehyde in the presence of lithium oxide, as high-performance anodes for rechargeable lithium ion batteries. During one-pot solid-phase interface reaction, Li2O was used to absorb the in-situ generating H2O enhancing the formation of Schiff-based networks and LiOH was in-situ obtained, which can be used as active agent to increase the BET surface areas of final carbons. The obtained NHPCs present 3D hierarchical honeycomb-like morphology, ultrahigh nitrogen content up to 12.2 wt%, large specific surface area of 1260 m2 g−1. These unique structural properties allowed for fast ion diffusion and rapid electron transport, and offered enriched active sites for lithium storage. NHPCs presented a high reversible capacity of 880 mAh g−1 at 100 mA g−1 even after 100 cycles, and exceptional rate capability with 301 mAh g−1 at 3000 mA g−1, outperforming most reported nano‑carbons. Therefore, this strategy will open a new way to prepare heteroatom-doped porous carbons with a controllable hierarchical structure, for high-performance energy storage.

Ultrahigh-Content Nitrogen-doped Carbon Encapsulating Cobalt NPs as Catalyst for Oxidative Esterification of Furfural.

It is an attractive and challenging topic to endow non-noble metal catalysts with high efficiency via a nitrogen-doping approach. In this study, a nitrogen-doped carbon catalyst with high nitrogen content encapsulating cobalt NPs (CoOx @N-C(g)) was synthesized, and characterized in detail by XRD, HRTEM, N2 -physisorption, ICP, CO2 -TPD, and XPS techniques. g-C3 N4 nanosheets act as nitrogen source and self-sacrificing templates, giving rise to an ultrahigh nitrogen content of 14.0 %, much higher than those using bulk g-C3 N4 (4.4 %) via the same synthesis procedures. As a result, CoOx @N-C(g) exhibited the highest performance in the oxidative esterification of biomass-derived platform furfural to methylfuroate under base-free conditions, achieving 95.0 % conversion and 97.1 % selectivity toward methylfuroate under 0.5 MPa O2 at 100 °C for 6 h, far exceeding those of other cobalt-based catalysts. The high efficiency of CoOx @N-C(g) was closely related to its high ratio of pyridinic nitrogen species that may act as Lewis basic sites as well as its capacity for the activation of dioxygen to superoxide radical O2 .- .

Facile synthesis of nitrogen-enriched nanoporous carbon materials for high performance supercapacitors

Mesoporous carbons with ultrahigh nitrogen content were prepared for supercapacitors through the hard template method. Silica nanoparticles were used as the hard template, and ethylenediamine and CCl4 served as precursor. Large amount of mesopores were generated through removing the silica nanoparticles with HF. The effect of carbonization temperature on the pore structure and nitrogen content and thus on the capacitive performance of supercapacitors were investigated. It was found that the higher carbonization temperature leads to an initial increase and then decrease of specific surface area and a continuous decrease in N content. The sample carbonized at 700 °C (NC700) shows the highest capacitance (306 F g−1) due to the higher surface area (533 m2 g−1) and ultrahigh N content (18.06%). The increase in specific surface area results in improvement of double-layer capacitance, while the N element increases the pseudocapacitance and the wettability of the carbons. In addition, NC700 shows excellent stability with 96.6% capacitance retention even after 10,000 cycles at a current density of 3 A g−1.