Nitrogen-containing Carbon Materials Research Articles

Cohydrothermal carbonization of defatted microalgae and glucose for the production of supercapacitor carbon material

Most research on the utilization of microalgae resources is the preparation of biodiesel, but this method will produce a large amount of defatted microalgae waste. This paper mainly studies the resource utilization of defatted microalgae waste, that is, through the cohydrothermal carbonization (C-HTC) of defatted Chlorella pyrenoidosa (DFCP) and glucose (G), to prepare nitrogen-containing carbon materials for the preparation of supercapacitor electrodes. The effects of feedstock, temperature, time, and G:DFCP mass ratio on the yield and properties of the hydrochar produced from the C-HTC of G and DFCP were examined. The hydrochar yield produced from the C-HTC of G and DFCP was 43 wt%, which is much higher than that of the HTC of G (34.0 wt%) and DFCP (25.5 wt%) alone due to the promotion of Maillard reactions between the derivatives produced from G and DFCP. The specific area and micropore volume played important roles in the specific capacitances of the activated hydrochars rather than the effect of heteroatomic doping. At a current density of 1 A/g, the activated hydrochar produced from the C-HTC of G and DFCP at 200 °C for 5 h (AHC-DFCP+G-200-5) achieved a specific capacity of 220.95 F/g. After 20,000 cycles at a charge density of 2 A/g, this kind of activated hydrochar still maintained an outstanding coulomb efficiency of 100 % and a good capacitance retention of 98.26 %. This study provides a new solution to the high-value-added utilization of defatted microalgae waste and the improvement of the economics of microalgae biorefinery.

Synthesis of highly-porous nitrogen-doped carbon materials by pyrolysis of melamine-formaldehyde resin using a hard template

The use of nitrogen-doped carbon materials as electrodes in supercapacitors is a promising area of research. In this study highly-porous nitrogen-containing carbon materials were obtained by pyrolysis of melamine formaldehyde resin in the presence of nanocrystalline MgO as a hard template that was washed off after the pyrolysis. Magnesium citrate was used as a precursor for the synthesis of the template agent in situ during the pyrolysis of the resin. The obtained materials were characterized by X-ray diffraction, BET nitrogen adsorption method and Raman spectroscopy. The presence of nitrogen in the amount of 4 atomic percent was proved by XPS spectroscopy. The specific surface area was found to increase monotonically from 10 to 1300 m2/g with an increase in the content of magnesium citrate in the initial mixture. The samples showed high capacitance of 120 F/g in 1 M H2SO4 electrolyte and can be used in supercapacitors.

Bottom-up synthesis of pyridinic nitrogen-containing carbon materials with C–H groups next to pyridinic nitrogen from two-ring aromatics

Carbon materials containing pyridinic nitrogen are expected to be effective for electrodes and catalysts. However, it is challenging to selectively and simultaneously introduce both pyridinic nitrogen and C–H groups next to the pyridinic nitrogen at a high content, which has been reported to work as an active site for oxygen reduction reaction, in the absence of catalysts. In this work, among six relatively inexpensive precursors with pyridinic N and two-fused rings, 1,5-naphthyridine showed the highest percentage of pyridinic nitrogen (80%) and the highest pyridinic-nitrogen content (12.4 at%) after carbonization in an ampoule at 873 K. Unlike carbon materials prepared from precursors with three- or more-fused rings, C–H groups next to pyridinic nitrogen remained in carbonized 1,5-naphthyridine with two-fused rings. Carbonization mechanisms of precursors with two-fused rings were quite different from those of precursors with three- or more-fused rings because of the low thermal stability of the precursors with two-fused rings as results of energy calculation and ReaxFF. The highest percentage and content of pyridinic nitrogen were attained using 1,5-naphthyridine because 1,5-naphthyridine had the highest thermal stability of C–N bonds and the low probability to form tertiary nitrogen among precursors with two-fused rings.

Ultrasensitive Luteolin Electrochemical Sensor Based on Novel Lamellar CuZn@ Nitrogen-Containing Carbon Nanosheets.

The Cu/Zn-zeolitic imidazolate framework (Cu/Zn-ZIF) was synthesized using the traditional hydrothermal method, and its surface morphology was controlled by adding polyvinylpyrrolidone (PVP) during its synthesis. It was then calcined at 800 °C to form the nitrogen-containing carbon material CuZn@NC, which improved the electron transfer rate. Scanning electron microscopy (SEM), X-ray crystal diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to investigate the surface morphology and structure. Finally, the electrochemical sensing platform for luteolin was effectively constructed by changing the metal-ion ratio during synthesis to achieve the most suitable electrode material. The sensor platform detects luteolin well, with an operating curve equation of Ip (A) = 0.0571C (nM) - 1.2913 and a minimum detection limit of 15 nM, and the platform has been successfully employed for luteolin detection in real samples.

Nitrogen‑containing species evolution during co-pyrolysis of gentamicin residue and biomass

In the present study, the nitrogen‑containing species evolution in gas-liquid-solid three phases during co-pyrolysis of gentamicin residue and typical biomass was thoroughly investigated. A series of methods for qualitative and quantitative analysis of nitrogen‑containing products were applied. Quaternary-N, pyrrolic-N and pyridinic-N in pyrolysis char, amides, N-heterocyclic chemicals and nitriles in bio-oils, as well as NH3 and HCN in gaseous products were identified. Obviously, the pyrolysis temperature was found to play a crucial role in nitrogen-containing species distribution, where high temperature contributed to the formation of nitrogen-containing species in gas and liquid phases. The plausible evolution avenue for nitrogen-containing species in three phases was also proposed. Furthermore, it is observed that the introduction of biomass (corn cob, corn straw and wheat straw) significantly facilitated the nitrogen transformation into the char from liquid products. In the case of gentamicin residue-to-corn cob mass ratio of 7:3, the nitrogen yield in co-pyrolysis char achieved 43.96 wt% at a temperature of 450 °C, demonstrating the effective fixation of nitrogen-containing species in the presence of biomass. This crucial finding supplies a feasible method for realizing the clean disposal of antibiotic residues and rational construction of nitrogen-containing carbon materials from solid wastes.

Microstructure Evolution and Its Correlation with Performance in Nitrogen-Containing Porous Carbon Prepared by Polypyrrole Carbonization: Insights from Hybrid Calculations.

The preparation of nitrogen-containing porous carbon (NCPC) materials by controlled carbonization is an exciting topic due to their high surface area and good conductivity for use in the fields of electrochemical energy storage and conversion. However, the poor controllability of amorphous porous carbon prepared by carbonization has always been a tough problem due to the unclear carbonation mechanism, which thus makes it hard to reveal the microstructure–performance relationship. To address this, here, we comprehensively employed reactive molecular dynamics (ReaxFF-MD) simulations and first-principles calculations, together with machine learning technologies, to clarify the carbonation process of polypyrrole, including the deprotonation and formation of pore structures with temperature, as well as the relationship between microstructure, conductance, and pore size. This work constructed ring expressions for PPy thermal conversion at the atomic level. It revealed the structural factors that determine the conductivity and pore size of carbonized products. More significantly, physically interpretable machine learning models were determined to quantitatively express structure factors and performance structure–activity relationships. Our study also confirmed that deprotonation preferentially occurred by desorbing the dihydrogen atom on nitrogen atoms during the carbonization of PPy. This theoretical work clearly reproduces the microstructure evolution of polypyrrole on an atomic scale that is hard to do via experimentation, thus paving a new way to the design and development of nitrogen-containing porous carbon materials with controllable morphology and performance.

Macroporous nitrogen-containing carbon for electrochemical capacitors

Polypyrrole-gelatin aerogels were synthesized by a one-step cryopolymerization approach and carbonized at various temperatures (100–700 °C). The mechanical integrity and macroporous morphology (pore size 4–16 µm) of materials carbonized at all studied temperatures were preserved after carbonization. Raman and X-ray photoelectron spectroscopies confirmed the aerogel conversion to carbon with gradually enhanced structural order at higher temperatures (300–600 °C). Change of the material conductivity with carbonization temperature follows the evolution of its molecular structure, reaching 2 × 10–5 S cm–1 for a fully carbonized aerogel (700 °C). Specific surface area and total pore volume values for the carbonized material were ⁓one order of magnitude higher (441.7 m2 g–1 and 0.21 cm3 g–1 at 600 °C, respectively) compared to the ones of the precursor. Cyclic voltammetry measurements showed that gravimetric capacitance of the products increased at higher carbonization temperatures up to 209 F g–1 (700 °C) and was stable for at least 1000 cycles. Galvanostatic charge-discharge method showed the highest capacitance 273 F g–1 (1 M HCl). The prepared nitrogen-containing carbon materials can be potentially used for supercapacitor applications.

Selective hydrogenation of vanillin to vanillyl alcohol over Pd, Pt, and Au catalysts supported on an advanced nitrogen-containing carbon material produced from food waste

Food waste worldwide has been threatening the environment and resulting in high carbon emissions. Although anaerobic fermentation is a potential solution transforming food waste into valuable chemicals, a large amount of the fermentation residue remains as solid waste. For closing the circular economy loop for food waste valorization, we proposed a thermo-chemical activation of a fermentation residue produced from a mixture of food waste and sludge to prepare a nitrogen-enriched, advanced carbon material. This could be used as a support to synthesize Pd/C, Pt/C and Au/C catalysts for the aqueous-phase hydrogenation of vanillin to vanillyl alcohol at mild reaction conditions. The produced alcohol increased sixfold the commercial value of the original aldehyde. The catalytic performance (based on the vanillin conversion and vanillyl alcohol yield) followed the order of Pd/C > Pt/C > Au/C. The Pd/C catalyst showed an excellent catalytic activity (>99% vanillin conversion and > 99% vanillyl alcohol selectivity) at optimized reaction conditions (i.e., 30 °C and 0.7 MPa H2 for 90 min, with 2 mmol vanillin/10 mg catalyst), along with high reusability and stability (up to four consecutive runs). These catalytic features outperformed those of a commercial Pd/C catalyst owing to: (i) high reduction degree and stabilization of the Pd particles on the carbon support, which accommodated a higher proportion of pyridinic than pyrrolic nitrogen, and (ii) rapid adsorption of the aldehyde group on the catalyst combined with rapid desorption of the newly formed hydroxymethyl group. This exceptional catalytic behavior was corroborated by efficient hydrogenation of other lignin-derived aromatic aldehydes, including p-hydroxybenzaldehyde and syringaldehyde, to their respective alcohols. Our results can bring a novel use for food waste in catalysis and represent a sustainable and efficient conversion of biomass into value-added chemicals and advanced materials.

Water on porous, nitrogen-containing layered carbon materials: the performance of computational model chemistries.

Porous, layered materials containing sp2-hybridized carbon and nitrogen atoms, offer through their tunable properties, a versatile route towards tailormade catalysts for electrochemistry and photochemistry. A key molecule interacting with these quasi two-dimensional materials (2DM) is water, and a photo(electro)chemical key reaction catalyzed by them, is water splitting into H2 and O2, with the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) as half reactions. The complexity of some C/N-based 2DM in contact with water raises special needs for their theoretical modelling, which in turn is needed for rational design of C/N-based catalysts. In this work, three classes of C/N-containing porous 2DM with varying pore sizes and C/N ratios, namely graphitic carbon nitride (g-C3N4), C2N, and poly(heptazine imides) (PHI), are studied with various computational methods. We elucidate the performance of different models and model chemistries (the combination of electronic structure method and basis set) for water and water fragment adsorption in the low-coverage regime. Further, properties related to the photo(electro)chemical activity like electrochemical overpotentials, band gaps, and optical excitation energies are in our focus. Specifically, periodic models will be tested vs. cluster models, and density functional theory (DFT) vs. wavefunction theory (WFT). This work serves as a basis for a systematic study of trends for the photo(electro)chemical activity of C/N-containing layered materials as a function of water content, pore size and density.

Bottom-Up Synthesis of Pyridinic Nitrogen-Containing Carbon Materials with Reactive C-H from Two-Ring Aromatics

Bottom-Up Synthesis of Pyridinic Nitrogen-Containing Carbon Materials with Reactive C-H from Two-Ring Aromatics

Unveiling bonding states and roles of edges in nitrogen-doped graphene nanoribbon by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) is among the most utilized analytical methods for nitrogen-doped carbon materials. Clarifying the assignments of nitrogen-doped carbon materials with different degrees of carbonization, which relates to conjugated systems, is essential to correlate structures with the performance of various applications, but such precise assignments were challenging. In this work, precise analyses were conducted to overcome the difficulty to assign the peaks of carbon materials with different degrees of carbonization, different edges, and various nitrogen-containing functional groups in graphene nanoribbons (GNRs), such as nitrile, pyridinic, primary with/without charges, secondary with/without charge, tertiary without charges (graphitic nitrogen), and quaternary nitrogen. Electrons donated from hydrogen and Madelung potentials showed a higher correlation to the peak shift of C1s and N1s XPS spectra than Mulliken charges on nitrogen. Zigzag edges showed a greater influence on the peak shift of tertiary amine (graphitic nitrogen) than armchair edges on XPS spectra. Besides, as the degree of carbonization is increased from aromatic compound-like structures to GNRs, the peak positions of C–N in C1s and N1s XPS spectra shifted to higher binding energies. This research proved that XPS could be applied to the precise structural analyses of nitrogen-containing carbon materials.

Monodispersed Nitrogen-Containing Carbon Capsules Fabricated from Conjugated Polymer-Coated Particles via Light Irradiation.

Near-infrared (NIR) light irradiation induced the transformation of polypyrrole (PPy) to nitrogen-containing carbon (NCC) material due to its light-to-heat photothermal property. The temperature of the PPy increased over 700 °C within a few seconds by the NIR laser irradiation, and elemental microanalysis confirmed the decreases of hydrogen and chloride contents and increases of carbon and nitrogen contents. Monodispersed polystyrene (PS)-core/PPy shell particles (PS/PPy particles) synthesized by aqueous chemical oxidative seeded polymerization were utilized as a precursor toward monodispersed NCC capsules. When the NIR laser was irradiated to the PS/PPy particles, the temperature rose to approximately 300 °C and smoke was generated, indicating that the PS component forming the core was thermally decomposed and vaporized. Scanning electron microscopy studies revealed the successful formation of spherical and highly monodispersed capsules, and Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy studies confirmed the capsules consisted of NCC materials. Furthermore, sunlight was also demonstrated to work as a light source to fabricate NCC capsules. The size and thickness of the capsules can be controlled between 1 and 80 μm and 146 and 231 nm, respectively, by tuning the size of the original PS/PPy particles and PPy shell thickness.

Super-activated CNB for CO2 capture: The development of the nitrogen containing porous carbon by chlorination and post KOH-activation

Minimization of carbon dioxide (CO2) emissions into the atmosphere is a prerequisite to solving climate change. Tremendous research has been conducted to capture the CO2 from pre- and post-combustion using nanoporous materials. Nitrogen-doped porous carbon is one of the most promising CO2 adsorbents. Achieving high nitrogen content and high micropore volume is essential to CO2 adsorption properties. In this study, super activated nitrogen and boron co-doped porous carbons (K-CNBs) are successfully synthesized by the chlorination and the subsequent KOH chemical activation. Nitrogen and boron co-doped porous carbons (CNBs) are synthesized by the chlorination of titanium carbonitride and boride mixture. CNBs good thermal and oxidation stability that induces an increase in the nitrogen content as well as an increase in the micropore volume even after the activation. K-CNBs, having both high micropore volume and abundant pyridonic-N functional group, show superior CO2 uptake at ambient temperature at atmospheric pressure with excellent CO2/N2 selectivity. K-CNBs are the best CO2 capturer among the nitrogen-containing carbon materials, reaching the threshold of CO2 uptakes performance.

Nitrogen-containing carbon nano-onions-like and graphene-like materials derived from biomass and the adsorption and visible photocatalytic performance

Nitrogen-containing carbon (NC) materials with different morphologies, nano-onions-like material with size of 20–30 nm and multilayered graphene-like materials with 2–5 layers, were prepared in the aid of Fe(NO3)3 through a facile hydrothermal method followed by calcination at low temperature. In the method, the eco-friendly biomass Lentinus edodes was used as carbon nitrogen source, Lentinus edodes isused as carbon-nitrogen source, and Fe(NO3)3 is used as nitrogen-fixing agent to fix the nitrogen in the biomass by Fe-N coordination and shape-regulating agent to regulate the morphology of goal materials, thereby catalyzing the conversion of biomass to NC materials. The adsorption and visible-light photocatalytic performance are investigated using phenol as the pollutant. The result shows that the nitrogen content in NC material with nano-onions-like reaches to 5.83%. The pyridinic N can be used as active sites while the hollow nano-onions structure can inhibit the desorption of phenol to improve the adsorption performance. Both unique structure and active site are beneficial to the adsorption ability. The photocatalytic performance shows that the degradation rate of nano-onions-like NC material for phenol reaches to 56.28% under visible-light irradiation, exhibits good visible-light photocatalytic performance than the others. The active species O2− plays important role in the photocatalytic degradation of phenol. And, the graphite N in NC material is helpful to separation of the photoelectrons and holes, enhancing the photocatalytic performance.

Yttrium fluoride doped nitrogen-contained carbon as an efficient cathode catalyst in zinc-air battery

Recently, advanced nitrogen-containing carbon materials create a huge opportunity for developing efficient catalysts, and show great potential in zinc-air batteries (ZABs). In this study, YF3 doped nitrogen-containing carbon (YF3@NC) electrocatalyst is prepared using m-phenylenediamine as nitrogen and carbon sources. Yttrium chloride, ammonium fluoride and l-arginine are used as Y source, F source and assistant, respectively. Spherical YF3 precursor is obtained through a facile arginine-assisted hydrothermal method, which is then coated with nitrogen-containing carbon and pyrolyzed at high temperature to fabricate YF3@NC. It exhibits a positive onset potential (0.943 V), half-wave potential (0.836 V), high current density and good cycling stability (10 h degradation: 13%). When YF3@NC is applied as air cathode electrode in ZABs, the obtained battery has a high open circuit potential (1.478 V) and peak power density (75 mW cm−2). This approach makes YF3@NC to be a promising candidate as cathode catalyst in ZABs in the future.

Preparation of nitrogen-containing carbon using a one-step thermal polymerization method for activation of peroxymonosulfate to degrade bisphenol A

Nitrogen-containing carbon materials (NCC-x) are promising metal-free catalysts for activation of peroxymonosulfate (PMS) to treat with aqueous organic pollutants. In this study, NCC-x were synthesized via a facile thermal polymerization method using urea and terephthalaldehyde as precursors. This method was derived from the polymerization method of graphitic carbon nitride (g-C3N4) and the reaction between the precursors was based on Schiff base chemistry. Compared with the synthesis of g-C3N4 using urea as the precursor, formation of a melamine ring was inhibited and the cyano groups were produced in NCC-x during the polymerization process. The obtained NCC-x catalysts had high specific surface areas, many graphite-nitrogen active sites, and high degrees of graphitization, thus exhibiting excellent activities for the degradation of bisphenol A via PMS activation. This study introduces a convenient method to obtain a highly efficient nitrogen-containing carbon PMS activator and the results are useful for the development of bisphenol A treatment by PMS activation using carbon-containing materials.

Front Cover: Green Conversion of Microalgae into High‐Performance Sponge‐Like Nitrogen‐Enriched Carbon (ChemElectroChem 3/2019)

The Front Cover shows sponge-like nitrogen-containing carbon materials prepared by using a one-step activation method from nitrogen-rich microalgae biomass. A large Brunauer–Emmett–Teller surface area of 865 m2/g is obtained with a high nitrogen content of 7.5 wt %. This research provides a convenient and ecofriendly way to prepare high-performance nitrogen-containing carbons. More information can be found in the Article by Y. Liu et al. on page 646 in Issue 3, 2019 (DOI: 10.1002/celc.201801272).

Nitrogen-containing three-dimensional biomass porous carbon materials as an efficient enzymatic biosensing platform for glucose sensing.

A novel glucose biosensor was developed by immobilizing glucose oxidase (GOD) on a three-dimensional (3D) porous cane vine (wisteria) stem-derived carbon (3D-CVS), which was firstly proposed as novel support material for electrochemical biosensors using loaded biomolecules. Here, an integrated 3D-CVS electrode was fabricated by loading GOD molecule onto a whole piece of 3D-CVS electrode for a glucose biosensor. The morphologies of integrated 3D-CVS and 3D-CVS/GOD electrode were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM results show the 3D macroporous structure of the integrated 3D-CVS electrode. TEM results show that there are some micro-holes and defects in the 3D-CVS electrode. Electrochemical behaviors and electrocatalytic performance of integrated 3D-CVS/GOD electrode were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. The effects of pH and scanning rate on the electrochemical response of biosensors have been studied in detail. The glucose biosensor showed a wide linear range from 0.58 μM to 16 mM, with a high sensitivity of 86.17 μA mM−1 and a low detection limit of 0.19 μM. Furthermore, the glucose biosensor exhibited high selectivity, good repeatability and nice stability.

Use of Nitrogen-Containing Carbon Supports To Control the Acidity of Supported Heteropolyacid Model Catalysts

Physical and chemical properties of heteropolyacids (HPAs), e.g., H3PMo12O40 supported on nitrogen-containing carbon materials, were investigated. Supports included nitrogen-doped graphitic carbons (N–C-1000 (2 N at. %) and N–C-600 (19 N at. %)) and mesoporous graphitic carbon nitride (mpgC3N4 (53 N at. %)). The ability to disperse HPAs without crystallite formation followed the trend N–C-600 < N–C-1000 ≈ activated carbon (C) < mpgC3N4. HPAs preferentially interact with pyridinic nitrogen and surface NH2 groups; the latter lead to ammonium HPA salt crystallites observed via X-ray diffraction (XRD). At low coverage, HPAs are molecularly dispersed on all four supports. At comparable polyoxometalate coverages, C and N–C-1000 showed similar dehydration/oxidation activities in methanol oxidation. However, N–C-600 and mpgC3N4 exhibited lower activities for both reactions. The much-greater decrease in dehydration vs oxidation activity on nitrogen-rich supports led to higher catalyst oxidation selectivities. This...

Knoevenagel condensation reactions catalyzed by nitrogen-containing mesoporous carbon materials under mild reaction conditions

A series of nitrogen-containing ordered mesoporous carbon (NOMC) materials have been prepared by a convenient soft-templating method. The physicochemical properties of the NOMC samples were characterized by N2 adsorption and desorption, small-angle XRD, FT-IR, XPS, and TEM. As solid base catalysts, NOMCs exhibited remarkable catalytic activities for Knoevenagel condensation reactions under mild reaction conditions, depending on their synthetic calcination temperature. Among them, NOMC-500 showed the highest catalytic activity. For Knoevenagel condensation of benzaldehyde and malononitrile, the conversion of aldehyde was higher than 85% under 50 °C. Moreover, the catalysts had good catalytic applicability for wide substrates. The catalytic activity obtained on NOMC catalyst is compared with other nitrogen-containing carbon-based materials. Nitrogen-containing ordered mesoporous carbon materials, prepared by a soft-templating method under aqueous solution and as solid base catalysts, demonstrated high catalytic activity in Knoevenagel condensation reactions under mild reaction conditions.