Nitrogen-doped Carbon Microspheres Research Articles

N-doped CNTs/CoNi nanochains-carbon hollow microspheres multi-level multi-scale heterogeneous interface structures and microwave absorption properties

Constructing multi-level multi-scale heterogeneous interfaces in magnetic carbon-based composites remains a formidable challenge, requiring rational material combinations to effectively balance dielectric and magnetic losses for achieving high strength and wide frequency wave absorption. Electromagnetic wave (EMW) absorbing materials consisted of cobalt-nickel (CoNi) magnetic nanochain, nitrogen-doped carbon nanotubes (NCNTs) and hollow carbon microspheres were prepared by hydrothermal method without external magnetic field. These composites possessed a unique multi-level multi-scale heterogeneous interface structure that is highly advantageous for efficient absorption of EMWs. The CoNi nanoparticles were self-assembled into uniformly distributed and randomly oriented magnetic nanochains, which were further reassembled with NCNTs and hollow carbon microspheres to form heterogeneous interface structures resembling a rose, chrysanthemum, hedgehog ball, and bauhinia tree. Due to the high-density interface enhancing the loss ability of interface polarization, as well as the higher saturation magnetization, coercivity, and wave absorption ability of the magnetic nanochains compared to the magnetic nanoparticles themselves, the minimum reflection loss achieved is −66.86 dB, and the effective absorption bandwidth achieved is 5.01 GHz, at a content as low as 11 wt%. This study provides a new idea for generating nanochains without magnetic fields and constructing multi-level and multi-scale heterogeneous interface structures to achieve strong absorption and wide effective absorption bandwidth (EAB).

Facile synthesis of self-nitrogen-doped carbon spheres for high-efficient photocatalytic CO2 reduction to CO

In this work, self-nitrogen-doped carbon microsphere photocatalysts were prepared by hydrothermal and carbonation pyrolysis with first application in photocatalytic CO2 reduction. Coupled with relevant characterization, nitrogen-doped carbon microspheres were successfully prepared and the introduction of nitrogen significantly improved the photogenerated charge separation efficiency and CO2 photoreduction to CO activity, leading to the highest photocatalytic reduction activity with a CO yield of 185.71 μmol g−1 (9 h) under simulated sunlight irradiation. More importantly, its performance remains at about 98 % after ten consecutive cycle tests, indicating the excellent active stability of self-nitrogen-doped carbon spheres. Possible mechanisms for photocatalytic reduction and the role of nitrogen in photocatalytic adsorption and reduction processes are analyzed and proposed. The research provides novel strategies for the design of bifunctional catalysts that offer robust adsorption and efficient reduction, enabling the sustainable conversion of CO2.

Surface-coated AlF3 nanolayers enable polysulfide confinement within biomass-derived nitrogen-doped hierarchical porous carbon microspheres for improved lithium-sulfur batteries

The electrically insulating and volumetric deformation of sulfur and the shuttle effect of the intermediate lithium polysulfide (LiPSs) have severely hindered the development of lithium-sulfur batteries (LSBs). Herein, a synergistic strategy of hierarchical porous nitrogen-doped carbon microspheres (PNCM) derived from low-cost biomass with surface-coated AlF3 nanolayer as a multifunctional sulfur host (denoted as PNCM@S@AlF3) was developed. The PNCM not only possesses an abundant pore structure, large surface area, and high electrical conductivity but also features an intrinsic N-doped and fluorinated framework, which effectively enhances the physical adsorption and chemical anchoring to LiPSs. In addition, the AlF3 nanolayer protects the open surface of the porous carbon to isolate sulfur species from the electrolyte to reduce irreversible losses while accelerating the redox kinetics of LiPSs through strong polar adsorption and bonding. Hence, the PNCM@S@AlF3 cathode exhibits an initial capacity as high as 1176.2 mAh/g at 0.2C, and the cycling stability and rate capability are superior to that of PNCM@S without AlF3 coating. Impressively, the PNCM@S@AlF3 cathode delivers stable long-term cycling performance at a high rate of 2C, with 95.6% capacity retention after 500 cycles. This work presents a facile, sustainable, and efficient synergistic strategy for developing advanced LSBs.

Efficient degradation of rhodamine B by MoS2 modified Co-MOF derived nitrogen-doped carbon activated peroxymonosulfate

How to improve the issues of ion agglomeration and metal ion leaching, and how to prepare cobalt-based catalysts with high reactivity and stability, are highly desired yet challenging. In this paper, MoS2 modified Co-MOF derived nitrogen-doped carbon (Co/PCN/MoS2) microspheres rich in active sites were prepared using a simple carbonation-hydrothermal method, with g-C3N4, MoS2 and Co-MOF to overcome the aforementioned limitations. The flower-like nanostructure of MoS2 contributed to exposing more marginal active sites, allowing the high dispersion of Co-MOF within its structure. Meanwhile, Mo4+/Mo6+ and S species coexisted in MoS2, which promoted the valence cycle and electron transfer process, and improved the catalytic activity of the composite. The successful synthesis of Co/PCN/MoS2 was proved by XRD, SEM and FTIR characterizations. The electrochemical performance analysis showed that Co/PCN/MoS2 exhibited higher redox capacity than MoS2, and Co/PCN/MoS2/PMS system achieved the degradation rate of RhB as high as 97.19% within 30 min, which is higher than that of Co-MOF/g-C3N4/PMS (80.67%), Co-MOF/MoS2/PMS (78.08%), Co-MOF/PMS (77.00%), g-C3N4/PMS (53.68%) and MoS2/PMS (28.10%) systems. It had good anti-interference ability against coexisting substances, achieved good degradation performance in a wide pH range (pH 2.0–10.0), and possessed excellent stability and reusability with RhB degradation rate of 91.10% after 5 cycles. The quenching test confirmed that non free radical 1O2 is the main ROS for RhB degradation. This work is expected to provide a new idea and direction for the design and development of metal-doped heterogeneous catalysts with high activity and stability.

Nitrogen-doped lychee-like saccharide-based carbon microspheres with high-performance microwave absorption

The reasonable design of multiple interfaces and heteroatom doping can substantially improve the wave-absorbing performance of electromagnetic wave (EMW) absorbing materials. As the carbon source of biomass, the carbon material with abundant oxygen-containing groups on the surface can be obtained by hydrothermal method, which is conducive to modification and design of the morphology. In addition, N-hydroxymethyl acrylamide contains rich N atoms and has good water solubility, which can be well combined with sugar to prepare high-performance wave-absorbing materials. In this study, D-xylose and glucose were used as carbon sources, water was used as solvent, N-hydroxymethyl acrylamide was added, and nitrogen-doped lychee-like saccharide-based carbon microspheres (LSCMs) were obtained by hydrothermal synthesis and high-temperature carbonization. LSCMs-2 with good EMW attenuation capability and impedance matching performance was obtained by controlling the proportion of different raw materials. Under the optimal filling conditions, the EMW absorber is only 2 mm thick and achieves a minimum reflection loss (RL min) of −47.44 dB at 13.84 GHz with an effective absorption bandwidth (EAB) of 12.24–17.36 GHz (5.12 GHz). The excellent EMW attenuation performance is mainly attributed to dipole polarization and interface polarization in the LSCMs. This research offers a new green synthesis route for the preparation of EMW absorbers with wider bandwidth, thinner thickness and better absorption performance.

Dissolution of alkali lignin in ionic liquid to fabricate nitrogen-doped carbon microspheres for electrochemical supercapacitors

Ionic liquids (ILs) have been extensively sought after for green solvents, catalysts, adsorbents, and carbon precursors. Herein, 1-ethyl-3-methylimidazolium acetate ([Emim][Ac])–lignin nitrogen-doped carbon microspheres (ECLMs) were easily synthesized through pre-oxidation and carbonization processes using a solution containing [Emim][Ac] and alkali lignin. The pre-oxidation process is analogous to the ionothermal carbonization method, wherein [Emim][Ac] serves as a reaction medium for preparing the ELCMs precursor. During the carbonization process, [Emim][Ac] served as a templating agent and heteroatom source to facilitate nitrogen doping and formation of micropores and mesopores. The as-synthesized ELCMs exhibits a considerably high specific surface area of 1267.2 m2/g and an optimal nitrogen-doping level of 2.21 %. This reveals its potential as a promising candidate for electrode materials in supercapacitor. The ELCMs demonstrate a remarkable specific capacitance of 262.5 F/g at 0.5 A/g and excellent rate capability in a three-electrode system. Additionally, the symmetric supercapacitor fabricated with electrode materials of ELCMs and a cellulose separator exhibits excellent cycling stability, with an impressive capacitance retention rate of 91.0 % after undergoing 5000 cycles at 5 A/g. Moreover, it achieves an ideal energy density of 4.17 Wh/kg at power density of 126 W/kg. This study investigates an effective strategy for designing and synthesizing different heteroatom-doped carbon materials from IL-biomass resources to enhance their applicability in energy storage devices.

CoFe2O4 decorated graphene/C18-functionalized mesoporous silica nanocomposites prepared for magnetic enrichment and electrochemical detection of promethazine in beef

Promethazine (PHZ) is used as a sedative in veterinary medicine, and its residue can threaten the health of human. The electrochemical detection of PHZ is suitable method for application in the field. However, the traditional electroanalysis is difficult to perform directly in meat samples due to matrix interference. This work integrates magnetic solid-phase extraction and differential pulse voltammetry for highly sensitive and selective determination of PHZ in beef and beef liver for the first time. CoFe2O4/graphene coated with C18-functionalized mesoporous silica (MG@mSiO2-C18) is synthesized as dispersed magnetic adsorbent to extract PHZ. Magnetic glassy carbon electrode modified with nitrogen-doped hollow carbon microspheres (HCM) attracts the MG@mSiO2-C18 with PHZ, and directly detects the PHZ without elution procedure. MG@mSiO2-C18 can separate PHZ to avoid the interference of impurities on following detection, and also concentrate PHZ on magnetic electrode. Additionally, the electrode modification with HCM can amplify the electrochemical signal of PHZ. Finally, the integrated PHZ determination method exhibits a wide linear range from 0.08 µmol/L to 300 µmol/L with a low limit of detection of 9.8 nmol/L. The beef sample analysis presents excellent recovery, demonstrating that this protocol is promising for the rapid and onsite detection of PHZ in real meat samples

Pd NPs encapsulated by COF in nitrogen-doped macroporous chitosan carbon microspheres act as an efficient and recyclable multifunctional catalyst

Developing efficient, recoverable, and versatile palladium catalysts is of great significance. In this paper, nitrogen-doped macroporous chitosan carbon microspheres (MCM) were prepared by emulsion polymerization method with polystyrene microspheres as a template. The core-shell structured MCM@Pd@COF catalysts were then prepared using a coral-structured COF shell layer to seal the Pd NPs in the channels of the MCM. The introduction of COF with good photocatalytic properties improved the stability of the material while imparting its photocatalytic properties without affecting its catalytic activity. MCM@Pd@COF efficiently catalyzed the Suzuki coupling reaction (Iodobenzene and phenylboronic acid, 98 % yield, TON = 6.7 × 105, TOF = 3.4 × 105 h−1), and the reduction of 4-nitrophenol (4-NP, reaction rate constant Kapp = 9.48 × 10−1 min−1). The kinetic study revealed that the reduction reaction of 4-NP by MCM@Pd@COF was compliant with the quasi-first-order kinetic model. Furthermore, MCM@Pd@COF removed up to 96.3 % of high concentrations of rhodamine B (RhB) within 30 min under visible light irradiation. Mechanistic investigation showed that MCM@Pd@COF efficiently promotes the production of O2– and OH radicals under visible light irradiation, which drives the photocatalytic degradation of organic dyes. There was no significant decrease in the catalytic activity of MCM@Pd@COF over the eight uses.

Mechanisms and degradation pathways of doxycycline hydrochloride by Fe3O4 nanoparticles anchored nitrogen-doped porous carbon microspheres activated peroxymonosulfate

Peroxymonosulfate (PMS) based advanced oxidation processes have gained widespread attention in refractory antibiotics treatment. In this study, Fe3O4 nanoparticles anchored nitrogen-doped porous carbon microspheres (Fe3O4/NCMS) were synthesized and applied to PMS heterogeneous activation for doxycycline hydrochloride (DOX-H) degradation. Benefitting from synergy effects of porous carbon structure, nitrogen doping, and fine dispersion of Fe3O4 nanoparticles, Fe3O4/NCMS showed excellent DOX-H degradation efficiency within 20 min via PMS activation. Further reaction mechanisms revealed that the reactive oxygen species including hydroxyl radicals (•OH) and singlet oxygen (1O2) played the dominant role for DOX-H degradation. Moreover, Fe(II)/Fe(III) redox cycle also participated in the radical generation, and nitrogen-doped carbonaceous structures served as the highly active centers for non-radical pathways. The possible degradation pathways and intermediate products accompanying DOX-H degradation were also analyzed in detail. This study provides key insights into the further development of heterogeneous metallic oxides-carbon catalysts for antibiotic-containing wastewater treatment.

SnO2 nanoparticles composited with biomass N-doped carbon microspheres as low cost, environmentally friendly and high-performance anode material for sodium-ion and lithium-ion batteries

The oxygen vacancy-riched tin dioxide (SnO2) nanoparticles composites with biomass nitrogen-doped carbon microspheres (SNC composite materials) were fabricated to enhance the electrochemical performance of SnO2 as anode materials for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs). The optimal SNC-2 electrode not only shows excellent electrochemical performance (reversible capacity of 557.1 mAh g−1 after 50 cycles at 0.05 A g−1, high-rate capability of 329.5 mAh g−1 and reversible capacity of 320 mAh g−1 after 1000 cycles even at a high current density of 1.0 A g−1) in SIBs, but also exhibits superior electrochemical performance in LIBs. Furthermore, ex-situ solid-state nuclear magnetic resonance (NMR) results (23Na, 19F and 119Sn MAS NMR spectra) reveal that the reversibility of the alloy NaxSn and SnO2, as well as the formation of NaF during the electrode reaction of SNC-2. The sodium peroxide (Na2O2) is probed by ex-situ solid-state NMR and ex-situ electron paramagnetic resonance (EPR) tests during the electrochemical process of SNC-2 electrodes for SIBs. An optimized reaction mechanism characterized by the formation of Na2O2 in SnO2 anodes for SIBs is proposed according to our work.

Lithiophilic onion-like carbon spheres as lithium metal uniform deposition host

Lithium metal is considered as a promising anode material for next-generation secondary batteries, owing to its high theoretical specific capacity (3860 mA h g−1). Nevertheless, the practical application of Li in lithium metal batteries (LMBs) is hampered by inhomogeneous Li deposition and irreversible “dead Li”, which lead to low coulombic efficiency (CE) and safe hazards. Designing unique lithiophilic structure is an efficient strategy to control Li uniformly plating /stripping. Here, we report the silver (Ag) nanoparticles coated with nitrogen-doped onion-like carbon microspheres (Ag@NCS) as a host to reduce the nucleation overpotential of Li for dendrite-free LBMs. The Ag@NCS were prepared by a simple one-step injection pyrolysis. The lithiophilic Ag is demonstrated to be priority selective deposition of Li in the carbon cage. Meanwhile, the onion-like structure benefits to uniform lithium nucleation and dendrite-free lithium during cycling. Impressively, we successfully captured lithium metal on different hosts at atomic scale, further proving that Ag@NCS can effectively and uniformly deposit Li. Besides, Ag@NCS show a superiorly electrochemical performance with a low nucleation overpotential (∼1 mV), high CE and stable cycling performance (over 400 cycles at 0.5 mA cm−2) compared to the Ag-free onion-like carbon in LMBs. Even under harsh conditions (1 mA cm−2, 4 mA h cm−2), Ag@NCS still present superior cycling stability for more than 150 cycles. Furthermore, a full cell composed of LiFePO4 cathode exhibits significantly improved voltage hysteresis with low voltage polarization. This work provides a new choice and route for the design and preparation of lithiophilic host materials.

Controlling the D-band for improved oxygen evolution performance in Ni modulated ultrafine Co nanoparticles embedded in Nitrogen-doped carbon microspheres

Despite the challenges on tuning the d-band structure of transition metals, the d-band is of great importance for promoting the interaction between catalytic and intermediates during the oxygen evolution reaction (OER) process. Herein, ultrafine Co nanoparticles embedded in the surface layer of nitrogen-doped carbon microspheres are prepared through an in-situ co-coordination strategy, and its d-band is modulated by introducing different Ni amounts. The introduction of Ni in the Co crystal lattice can tune the d-band center and unpaired electrons, which collectively result in an enhancement of OER activity and kinetics. By investigating the catalysts with Ni content from 0% to 75%, it is concluded that the catalyst with 25% Ni shows optimal OER activity, lower overpotential (285 mV at 10 mA cm−2) and higher current densities (73.75 mA cm−2 at 1.63 V). Moreover, the good stability is also demonstrated with the negligible decrease on current densities after 3000 CV cycles or 100 h of continuous test in alkaline media. This concept of modulating the d-band structure by introducing a transition metal with different contents in another transition metal crystal lattice could present an alternative pathway to the development of highly active catalytic materials for OER and beyond.

Green self-activation engineering of metal–organic framework derived hollow nitrogen-doped carbon spheres towards supercapacitors

Hollow nitrogen-doped carbon microspheres are fabricated via a green self-activation strategy, and exhibit attractive electrochemical properties for aqueous supercapacitors.

Cobalt-embedded hierarchically-porous hollow carbon microspheres as multifunctional confined reactors for high-loading Li-S batteries

Abstract The shuttle effect of dissolved polysulfides migrating to and depositing on anodes often leads to low round-trip efficiency and short cycle life for lithium-sulfur (Li-S) batteries. Herein, we report the rational design of cobalt-embedded nitrogen-doped hollow carbon microspheres (Co@N-HCMSs) as a multifunctional sulfur host for Li-S batteries. The hollow carbon microspheres exhibit large central cavities wrapped by a hierarchically porous shell, showing a large surface area of 1954 m2 g−1. Furthermore, the carbon shells display a unique porous architecture, in which small pores are scattered on the outside and large pores are inside, thereby functioning as a selection barrier to confine polysulfides and diffuse Li+ simultaneously. Moreover, the highly dispersed cobalt nanoparticles in the porous shell activate the surrounding N-doped carbon layer, which not only promote chemical adsorption of polysulfides but also catalyze polysulfide conversion. This facilitation effect has been confirmed by Bader charge and density function theory (DFT) calculations. When applied in Li-S batteries, the sulfur-impregnated Co@N-HCMSs cathode material exhibits excellent electrochemical performances, especially with a high sulfur content of 90.5 wt% and a high areal sulfur loading of 5.1 mg cm−2.

Improving the performance of lithium ion capacitor by stabilizing anode working potential using CoSe2 nanoparticles embedded nitrogen-doped hard carbon microspheres

Lithium-ion capacitors (LIC) have problems such as the imbalance of electrochemical kinetics between the battery-type anode and the capacitive cathode, and the large change in the working potential of the hard carbon anode during charge and discharge, which limit the improvement of electrochemical performance for LIC. To solve these problems, CoSe2 nanoparticles embedded nitrogen-doped hard carbon microspheres (NCS-CoSe2) are synthesized and used as the anode material of LIC. Electrochemical tests show that NCS-CoSe2 has a reversible specific capacity of as high as 500 mAh g−1 at a current density of 1 A g−1, which can effectively stabilize the working potential of the anode. At a high working voltage window of 2.2–4.5 V, the potential change of the NCS-CoSe2 anode is as low as 0.35 V, significantly smaller than that of the pure hard carbon (0.87 V). Regarding the electrode kinetics, the NCS-CoSe2 anode is matched with the active carbon cathode well. When the power density rises sharply from 335 W kg−1 to 6700 W kg−1, the energy density of NCS-CoSe2//AC LIC can attain 82 Wh kg−1 (56.9% of initial energy density).

Silicon nanoparticle self-incorporated in hollow nitrogen-doped carbon microspheres for lithium-ion battery anodes

In this study, Silicon nanoparticles (Si NPs) were homogeneously self-incorporated into melamine–formaldehyde resin microspheres using a facile hydrothermal technique, followed by annealing the precursors to form hollow nitrogen-doped carbon microspheres (hNC MSs) containing approximately 10.8 wt.% Si NPs (Si@hNC MSs). Melamine was directly polymerized with formaldehyde, providing N and C sources for Li-ion battery anodes. Electrochemical tests demonstrated that the Si@hNC MS anode delivered a high reversible capacity of 872 mAh g–1 at a current density of 200 mA g–1 after 360 cycles. The hNC MSs largely limited the Si volumetric changes caused by repeated charging and discharging, resulting in the high electrochemical stability of the Si anode. This work demonstrates that melamine–formaldehyde resins can be used directly as C and N sources and can effectively mitigate the Si volumetric expansion. Moreover, we believe that this unique resin, an effective C source, has promising potential for improving the electrochemical performance of other metal or metal-oxide anodes.

Preparation of submicron monodisperse melamine resin microspheres and nitrogen-doped carbon microspheres derived from them

Preparation of submicron monodisperse melamine resin microspheres and nitrogen-doped carbon microspheres derived from them

Nitrogen-Doped Mesoporous Carbon Microspheres by Spray Drying-Vapor Deposition for High-Performance Supercapacitor.

Nitrogen-doped mesoporous carbon microspheres have been successfully synthesized via a spray drying-vapor deposition method for the first time, using commercial Ludox silica nanoparticles as hard templates. Compared to freeze-drying and air-drying methods, mesoporous carbon with a higher packing density can be achieved through the spray drying method. Vapor deposition of polypyrrole followed by carbonization and etching is beneficial for the generation of ultra-thin carbon network. The mesoporous carbon microspheres possess a mesopore-dominate (95%) high surface area of 1528 m2 g−1, a wall thickness of 1.8 nm, and a nitrogen content of 8 at% in the framework. Benefiting from the increased apparent density, high mesopore surface area, and considerable nitrogen doping, the resultant mesoporous carbon microspheres show superior gravimetric/volumetric capacitance of 533.6 F g−1 and 208.1 F cm−3, good rate performance and excellent cycling stability in electric double-layer capacitors.

Hierarchical porous nitrogen-doped carbon microspheres after thermal rearrangement as high performance electrode materials for supercapacitors

Polyimides have been used as the precursor of carbon materials. Thermal rearrangement polymers with porous structure can be prepared by thermal treatment of hydroxyl-containing polyimides in the solid state. Herein, hydroxyl-containing polyimides with hierarchical microspheres were firstly prepared by solvothermal method. After thermal rearrangement at 450 °C and further carbonization, the hierarchical porous nitrogen-doped carbon microspheres were obtained, which showed good electrochemical characteristics. The effects of the concentration of polymer solution, thermal rearrangement time and final carbonization temperature on the structure and properties of final carbon materials were investigated. The hierarchical porous carbon materials were tested as an electrode for supercapacitors, and HPI-45–2-800 with high specific surface area of 877 m2 g−1 exhibited excellent electrochemical properties. The specific capacitance of HPI-45–2-800 was 211.3 F g−1 at the current density of 0.5 A g−1. When the current density was increased to 10 A g−1, the retention rate of specific capacitance was as high as 55%. After 10,000 cycles of charging and discharging, the specific capacitance of HPI-45–2-800 electrode was still retained 99.94% of the initial capacitance, showing excellent long-term charge–discharge cycling stability. The hierarchical porous nitrogen-doped carbon microspheres after thermal rearrangement are expected to be high performance electrode materials for supercapacitors.

Hierarchically Structured Nitrogen-Doped Carbon Microspheres for Advanced Potassium Ion Batteries

Because of their unique properties, microstructured carbons have received widespread attention in various fields, such as energy storage, medicine, and biosensors. In this study, hierarchically str...