Nitrogen-containing Carbon Research Articles

ZnCl2-assisted conversion of nitrogen-containing biomass carbon from marigold flower: Toward highly porous activated nitrogen-doped carbon for low ESR and enhanced energy density supercapacitors

Herein, we report the synthesis and characterization of hierarchical porous activated nitrogen-doped carbon from pyrolysis of dried marigold flower precursor as an effect of different impregnation zinc chloride (ZnCl2) (1:1, 1:3 and 1:5) named FZ11, FZ13, and FZ15. BET and FESEM show the enhancement in porosity and surface area with activation with highest specific surface area of 1274.45m2/g for FZ15. XPS confirms the engineering of nitrogen content into functional nitrogen doped sites upon the action of ZnCl2 activation as N-reservoir which results in increase in specific capacitance of fabricated symmetric cell (without any conductive black) increases with activation and shows the highest specific capacitance of 179 F/g, energy density of 23 Wh/kg and power density of 556 W/kg for FZ15 sample. Addition of carbon black helps in lowering ESR to 0.77 Ω and enhancement in energy density and series combination of 3 such cells glow yellow LED for ~3 min.

Activating Fe activity and improving Ni activity via C3N4 substrate in alkaline oxygen evolution catalyzed by Ni-Fe phosphide

Ni phosphides have recently attracted considerable attention as promising catalysts for the oxygen evolution reaction (OER) and are generally promoted by Fe incorporation. However, the catalytic performance of nickel phosphide still does not meet the desired expectations. Additionally, the catalytic activity of iron (Fe) is insignificant and can be disregarded. In this study, we used C3N4 as a carbon substrate to modulate the 3d electron configurations and adsorption properties of Ni and Fe. Density functional theory (DFT) analysis reveals that the catalytic performance of Ni sites can be enhanced by utilizing the C3N4 substrate. Surprisingly, the Fe sites can also be activated to catalyze OER through a direct O2 mechanism and the catalytic activity of Fe is found to surpass that of Ni. As a result, the FeNi-C3N4-P catalyst demonstrated remarkable catalytic performance for OER. It exhibited a Tafel slope of 40.4 mV dec−1, an overpotential of 235 mV at 100 mA cm−2, and exhibited exceptional stability. This study highlights the activation of Fe and the enhancement of Ni by utilizing nitrogen-containing carbon substrates. This strategy offers promising prospects for the development of efficient Ni/Fe-based OER catalysts.

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.

Conductivity of carbonized and activated leather waste

The conductivity of chromium-tanned pigskin leather waste carbonized in various manner to nitrogen-containing carbons is reported. Four protocols have been tested: (1) The simple carbonization at 800 °C in inert atmosphere, (2) the carbonization at 500 °C followed by the activation with potassium hydroxide at 800 °C, (3) direct activation with the alkali at 800 °C and (4) the similar activation with potassium hydroxide excess. The fibrous collagen morphology was preserved after the carbonization except for some shrinkage. The yield in the simple carbonization, 26.9 wt%, was reduced to 23.9 wt% for the activated products. Elemental analysis indicated reduced content of organic elements after carbonization, and X-ray fluorescence the composition of growing inorganic part. The chromium content in biochar was close to 12 wt% and the X-ray diffraction revealed also the presence of metallic chromium in addition to expected chromium(III) oxide and sulfide. FTIR and Raman spectroscopies demonstrated the typical pattern of carbonized materials. The specific surface area and pore volume increased after the activation. The resistivity of the powdered carbonized leather was determined in four-point van der Pauw setup. It decreased by more than one order of magnitude as applied pressure increased from 0.1 to 10 MPa. The sample conductivity depended only a little on the way of carbonization and was of the order of tenths to units S cm−1 at 10 MPa. The precarbonization followed by the activation provided the best result with respect to the yield, nitrogen-content, specific surface area and conductivity of the carbonized material.

Improvement of Hybrid Electrode Material Synthesis for Energy Accumulators Based on Carbon Nanotubes and Porous Structures.

Carbon materials are promising for use as electrodes for supercapacitors and lithium-ion batteries due to a number of properties, such as non-toxicity, high specific surface area, good electronic conductivity, chemical inertness, and a wide operating temperature range. Carbon-based electrodes, with their characteristic high specific power and good cyclic stability, can be used for a new generation of consumer electronics, biomedical devices and hybrid electric vehicles. However, most carbon materials, due to their low electrical conductivity and insufficient diffusion of electrolyte ions in complex micropores, have energy density limitations in these devices due to insufficient number of pores for electrolyte diffusion. This work focuses on the optimization of a hybrid material based on porous carbon and carbon nanotubes by mechanical mixing. The purpose of this work is to gain new knowledge about the effect of hybrid material composition on its specific capacitance. The material for the study is taken on the basis of porous carbon and carbon nanotubes. Electrodes made of this hybrid material were taken as an object of research. Porous carbon or nitrogen-containing porous carbon (combined with single-, double-, or multi-layer carbon nanotubes (single-layer carbon nanotubes, bilayer carbon nanotubes or multilayer carbon nanotubes) were used to create the hybrid material. The effect of catalytic chemical vapor deposition synthesis parameters, such as flow rate and methane-to-hydrogen ratio, as well as the type of catalytic system on the multilayer carbon nanotubes structure was investigated. Two types of catalysts based on Mo12O28 (μ2-OH)12{Co(H2O)3}4 were prepared for the synthesis of multilayer carbon nanotubes by precipitation and combustion. The resulting carbon materials were tested as electrodes for supercapacitors and lithium ion intercalation. Electrodes based on nitrogen-containing porous carbon/carbon nanotubes 95:5% were found to be the most efficient compared to nitrogen-doped porous carbon by 10%. Carbon nanotubes, bilayer carbon nanotubes and multilayer carbon nanotubes synthesized using the catalyst obtained by deposition were selected as additives for the hybrid material. The hybrid materials were obtained by mechanical mixing and dispersion in an aqueous solution followed by lyophilization to remove water. When optimizing the ratio of the hybrid material components, the most effective porous carbon:carbon nanotubes component ratio was determined.

Conductivity of leather waste carbonized at various temperature: A challenge to conducting polymers

The pigskin leather was carbonized in inert atmosphere at temperatures up to 1200 °C in order to produce conducting nitrogen-containing carbons. The yield of the solid char was close to 30 wt% at 400 °C and remained still above 20 wt% even at the highest temperature. The original morphology of collagen fibres was preserved except for some shrinkage. The changes in the molecular structure were followed by FTIR spectra. Raman spectra reflected the conversion of the biopolymer to carbon. Specific surface area of carbonized products was low, of the order units m2g−1. The four-point setup was applied to evaluate the resistivity of samples as a function of pressure applied up to 10 MPa. The resistivity decreased with increasing pressure and corresponding double logarithmic presentations were linear. Electrical properties were found to be comparable with conducting polymers, such as polypyrrole. The conductivity of the product carbonized at 1000 °C and 1200 °C compressed at 10 MPa reached 5.3 and 11.2 S cm−1, close to the conductivity globular polypyrrole or polypyrrole nanotubes under the same conditions. The biochar obtained after the carbonization of leather waste thus can compete with conducting polymers when it comes to applications relying on electrical properties.

Green Synthesis of Carbon Quantum dots Derived from Lycium barbarum for Effective Fluorescence Detection of Cr (VI) Sensing.

Green and economical self-doped nitrogen-containing fluorescent carbon quantum dots (N-CQDs) were synthesized using a one-pot hydrothermal treatment method. The optical and structural properties of the N-CQDs were investigated in detail by UV-vis and fluorescence spectroscopy, X-ray diffraction (XRD) techniques, transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) spectroscopy, and elemental analysis illustrate the surface function and composition of N-CQDs. N-CQDs emit a broad fluorescence between365 ̴ 465nm and fluoresce most strongly at the excitation wavelength of 415nm. Meanwhile, Cr (VI) could significantly burst the fluorescence intensity of N-CQDs. N-CQDs showed an excellent sensitivity and selectivity to Cr (VI), which exhibited good linearity in the range of 0 ̴ 40 µmol/L with a detection limit of 0.16 µmol/L. In addition, the mechanism of Fluorescence quenching of N-CQDs by Cr (VI) was investigated. This work well provides a research idea for the preparation of green carbon quantum dots from biomass and their use for the detection of metal ions.

SYNTHESIS OF NITROGEN-CONTAINING CARBON BY SOLUTION PLASMA PROCESS AT VARIOUS PULSE REPETITION RATES

The solution plasma process (SPP) has attracted considerable attention for the synthesis of carbon nanomaterials; the SPP uses electrical discharges generated directly by a bipolar pulsed power supply for various combinations of the solvents and solutes in the solution. However, the SPP requires high-temperature heat treatment for enhancing conductivity and exhibiting catalyst activity. Furthermore, the metal used as the electrode in the SPP is generally sputtered during discharge. This study presents the feasibility of reducing the heat-treatment step and solving the problem of sputtering of the metal electrodes by simply increasing the repetition frequency of the bipolar pulsed power. During synthesis, the pulse frequency acts as the graphitization catalyst. The enhancement of crystallinity was further confirmed by X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The findings of this study are expected to contribute toward research on improving the properties of carbon for various applications of the SPP synthesis methods.

SORPTION PROPERTIES OF OXIDIZED AND NON-OXIDIZED ACTIVATED CARBON FOR COPPER(II) IONS

The problem of obtaining effective sorption materials is relevant in connection with the growing volumes of industrial wastewater and the development of individual technologies for their purification, including sorption methods. Activated carbon has established itself as a unique sorbent with a high sorption capacity for compounds of various nature. Modification of its surface, its oxidation leads to an increase in adsorption activity. The aim of this work is to compare the sorption properties of oxidized and non-oxidized activated carbon with respect to copper(II) ions. The concentration of Cu(II) ions in the solution was determined by atomic absorption analysis on an MGA-915 spectrometer. The degree of coal oxidation was characterized by the value of the static exchange capacity. Studies on the model synthetic nitrogen-containing carbon SKN showed the presence of different amounts of oxygen-containing surface functional groups: weakly acidic (lactonic) ‒COO‒; strongly acidic (carboxylic) ‒COOH; phenolic ‒OH. It is shown that without access to oxygen, the mechanisms of interaction of activated carbon of different oxidation states with Cu(II) ions are different: when weakly oxidized carbon is used, reductive sorption occurs, and if highly oxidized carbon serves as a sorbent, ion exchange occurs. It was found that for SKN coal with a low oxygen content, the boundary sorption of Cu(II) ions in a deaerated medium is about 40 mg/g; in the presence of oxygen, it decreases to 6 mg/g. An increase in the proportion of carboxyl and phenolic groups leads to an increase in the sorption of Cu(II) ions. Reductive sorption of copper(II) from aerated solutions is thermodynamically prohibited. It is recommended to use additional oxidation of coal to increase the content of PFG and the sorption capacity of the sorbent. For the extraction of copper(II) from aqueous technological solutions, carbon materials with a sufficient amount of oxygen-containing functional groups of various nature are most effective.

Tailored synthesis of a palladium catalyst supported on nitrogen-doped carbon nanotubes for gas-phase formic acid decomposition: A strong influence of a way of nitrogen doping

Palladium catalysts supported on different nitrogen-containing carbon nanotubes (N-CNTs) were successfully used in the continuous gas-phase formic acid decomposition for hydrogen production. A strong influence of a way of carbon tubes doping by nitrogen on the activity of catalysts comprising metallic nanoparticles of ca. 1 nm in size and single-atom Pd2+ species was found. A key role of the single-atom species, demonstrating excellent stability in various chemically aggressive media, in the catalyst activity was discovered when bamboo-like N-CNTs synthesized by catalytic chemical vapor deposition were used as a support. A substantial increase in the activity of Pd nanoparticles was achieved by the use of N-СNTs prepared by the post-treatment of oxidized multiwalled carbon nanotubes by ammonia resulting in the formation of the dominating surface amine groups. The combination of the electron-rich palladium nanoparticles and surface amine groups leads to an increase in the TOF value by a factor of 7 at 70 °C. The catalyst operates stable at >99 % selectivity to hydrogen with the mass specific performance 200 l H2/gPd ⋅ h.

Nitrogen-containing carbon nanofibers as supports for bimetallic Pt-Mn catalysts in aqueous phase reforming of ethylene glycol

Aqueous phase reforming (APR) of ethylene glycol was performed at 225 °C and 30 bar in batch and continuous reaction conditions. The effect on the APR performance by functionalizing carbon supports with nitrogen and adding Mn to Pt-based catalysts was investigated. The presence of nitrogen species on the carbon surface and Mn-addition (PtMn) improved the catalytic activity and promoted H2 production. XPS results suggest that the enhancement of the catalytic activity may be attributed to charge transfer from platinum to the nitrogen groups and Mn. Pt-based catalysts were stable under the studied reaction conditions, while up to 97 % of the manganese leached into the liquid solution during APR. However, the catalytic activity was maintained even with such significant decrease in Mn content, indicating that only a small amount of Mn is necessary to maintain the promotional effect on Pt during APR.

Promoting amorphization of commercial TiO2 upon sodiation to boost the sodium storage performance

Anatase TiO2 is a promising anode material for sodium-ion batteries, yet the low electronic and ionic conductivities are the main obstacles for its practical application. Even though the amorphization of TiO2 upon sodiation has already been observed, its underneath mechanisms are not fully elucidated. Herein, a low-cost nitrogen-containing carbon source of polyacrylonitrile is adopted to modify commercial anatase TiO2 by a convenient and nontoxic ball-milling technique combined with subsequent annealing treatment. In particular, the employment of a nitrogen-doping approach accompanied by nitrogen-doped carbon coating, results in a greatly improved conductivity, overall leading to a high reversible capacity of about 260 mA h g−1 at 25 mA g−1, superior rate capabilities, and an ultra-stable capacity of about 186 mA h g−1 after 1600 cycles at 500 mA g−1. Detailed characterizations denote that the improved conductivity as well as the small size of the synthesized TiO2 grains play a key role in the TiO2 amorphization upon sodiation, with the TiO2/C nanocomposite undergoing a complete amorphization in just few cycles. Finally, the irreversible amorphization of TiO2 is confirmed to be a crucial ingredient facilitating the Na+ diffusion kinetics and pseudocapacitive behavior, thus boosting the sodium storage performance.

Effect of Nitrogen-Containing Carbon Shell-Coated Carbon Support on the Catalytic Performance of Platinum–Cobalt Alloy Catalyst for Oxygen Reduction

Effect of Nitrogen-Containing Carbon Shell-Coated Carbon Support on the Catalytic Performance of Platinum–Cobalt Alloy Catalyst for Oxygen Reduction

Carbonized Leather Waste: A Review and Conductivity Outlook.

The carbonization of collagen-based leather waste to nitrogen-containing carbon is reviewed with respect to the preparation, characterization of carbonized products, and applications proposed in the literature. The resulting nitrogen-containing carbons with fibrous morphology have been used as adsorbents in water pollution treatment, in electrocatalysis, and especially in electrodes of energy-storage devices, such as supercapacitors and batteries. Although electrical conductivity has been implicitly exploited in many cases, the quantitative determination of this parameter has been addressed in the literature only marginally. In this report, attention has been newly paid to the determination of conductivity and its dependence on carbonization temperature. The resulting powders cannot be compressed into pellets for routine conductivity determination. A new method has been used to follow the resistivity of powders as a function of pressure up to 10 MPa. The conductivity at this pressure increased from 9.4 × 10-8 S cm-1 for carbonization at 500 °C to 5.3 S cm-1 at 1000 °C. The conductivity of the last sample was comparable with conducting polymers such as polypyrrole. The carbonized leather thus has the potential to be used in applications requiring electrical conduction.

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.

Adsorptive removal of oxytetracycline in wastewater by Cu/Al doped carbon microspheres prepared from low-molecular-weight chitosan

A series of Cu/Al doped nitrogen-containing carbon microspheres prepared from low-molecular-weight chitosan (Cu/Al@NC-x, x = 1, 2, 3) were synthesized by a facile one-pot hydrothermal strategy and used for the adsorptive removal of oxytetracycline (OTC) contaminants to polish up the quality of water. Batch adsorptive experiments were performed to appraise the potential of Cu/Al@NC-x as an effective adsorbent for OTC. The effects of initial OTC concentration, solution pH, coexisting ions, adsorption time, and temperature on adsorptive performance were systematically studied. Cu/Al@NC-2 possessed the highest adsorption performance for OTC with maximum equilibrium adsorption capacity of 1727.65 mg g−1 (25 °C), 2583.10 mg g−1 (35 °C), and 2900.84 mg g−1 (45 °C), respectively. The kinetics and isotherm simulation data complied well with the pseudo-second-order kinetic and Langmuir isotherm models, respectively. The thermodynamic analysis (ΔH° > 0, ΔG° < 0) illustrated the spontaneous endothermic process of Cu/Al@NC-2 adsorbing OTC. Especially, Cu/Al@NC-2 still retained an excellent removal efficiency of 92.25 % for OTC after five adsorption cycles, verifying the feasibility of Cu/Al@NC-2 in antibiotic wastewater treatment.

Construction of multiple active sites by solution-free self-generating dual-template strategy: Boosting the ORR performance of NiFe/N-doped 3D porous carbon nanosheets

The oxygen reduction reaction (ORR) that occurs at the cathode of fuel cells has vital influence on the overall performance of the related electrochemical energy conversion devices. Metal-nitrogen-carbon (M-N-C) catalysts are expected to take the place of traditional expensive commercial Pt-C as a new generation of ORR electrocatalyst. In this paper, a self-generating dual-template strategy was used to efficiently synthesize NiFe/N-doped 3D porous carbon nanosheets. In the specific synthesis process, the precursor of PBA (Ni3[Fe(CN)6]2) and the protective nitrogen-containing carbon source can be used as a primary pore-forming agent for in-situ forming of pore for the catalyst. The KCl and FeNi alloy produced in the synthesis process can also be used as an in-situ secondary template for pore forming of the electrocatalyst. The self-generating dual-template can not only produce porous structure to provide more interfaces and improve mass transfer, but also fabricate more active sites provided by N-doping and bimetal. The obtained NiFe/N-doped 3D porous carbon nanosheet (NFCN-MP4000) exhibits excellent electrocatalytic methanol tolerance and durability in alkaline electrolytes. Its ORR activity was comparable to that of commercial Pt/C (20 wt%), and showed a limiting current density superior to that of Pt/C (6.10 mA cm−2). This work provides a strategy for the construction of electrocatalytic materials with high performance for methanol tolerance and durability.

Nitrogen-containing nanoporous carbons synthesized from direct carbonization of non-porous coordination polymers for CO2 capture

Nitrogen-containing nanoporous carbons synthesized from direct carbonization of non-porous coordination polymers for CO2 capture

Hygroscopicity of nitrogen-containing organic carbon compounds: o-aminophenol and p-aminophenol.

Nitrogen-containing Organic Carbon (NOC) is a major constituent of atmospheric aerosols and they have received significant attention in the atmospheric science community. While extensive research and advancements have been made regarding their emission sources, concentrations, and their secondary formation in the atmosphere, little is known about their water uptake efficiencies and their subsequent role in climate, air quality, and visibility. In this study, we investigated the water uptake of two sparingly soluble aromatic NOCs: o-aminophenol (oAP) and p-aminophenol (pAP) under subsaturated and supersaturated conditions using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) and a Cloud Condensation Nuclei Counter (CCNC), respectively. Our results show that oAP and pAP are slightly hygroscopic with comparable hygroscopicities to various studied organic aerosols. The supersaturated single hygroscopicity parameter (κCCN) was measured and reported to be 0.18 ± 0.05 for oAP and 0.04 ± 0.02 for pAP, indicating that oAP is more hygroscopic than pAP despite them having the same molecular formulae. The observed disparity in hygroscopicity is attributed to the difference in functional group locations, interactions with gas phase water molecules, and the reported bulk water solubilities of the NOC. Under subsaturated conditions, both oAP and pAP aerosols showed size dependent water uptake. Both species demonstrated growth at smaller dry particle sizes, and shrinkage at larger dry particle sizes. The measured growth factor (Gf) range, at RH = 85%, for oAP was 1.60-0.74 and for pAP was 1.53-0.74 with increasing particle size. The growth and shrinkage dichotomy is attributed to morphological particle differences verified by TEM images of small and large particles. Subsequently, aerosol physicochemical properties must be considered to properly predict the droplet growth of NOC aerosols in the atmosphere.

N-Doped porous carbons obtained from chitosan and spent coffee as electrocatalysts with tuneable oxygen reduction reaction selectivity for H2O2 generation.

Nitrogen-containing porous carbons prepared by the pyrolysis of adequate biopolymer-based precursors have shown potential in several electrochemical energy-related applications. However, it is still of crucial interest to find the optimal precursors and process conditions which would allow the preparation of carbons with adequate porous structure as well as suitable nitrogen content and distribution of functional groups. In the present work we suggested a straightforward approach to prepare N-doped porous carbons by direct pyrolysis under nitrogen of chitosan : coffee blends of different compositions and using KOH for simultaneous surface activation. The synthetized carbon materials were tested for the electrochemical oxygen reduction to hydrogen peroxide (H2O2). A higher fraction of chitosan in the precursor led to a decrease in meso- and nano-porosity of the formed porous carbons, while their activity towards H2O2 generation increased. The nitrogen species derived from chitosan seem to play a very important role. Out of the synthesized catalysts the one with the largest content of pyridinic nitrogen sites exhibited the highest faradaic efficiency. The faradaic efficiencies and current densities of the synthesized materials were comparable with the ones of other commercially available carbons obtained from less renewable precursors.