N-doped Mesoporous Carbon Spheres Research Articles

Mesoporous carbon spheres modified with atomically dispersed iron sites for efficient electromagnetic wave absorption

Carbon materials have obtained some achievements in electromagnetic wave (EMW) absorption owing to their excellent electrical conductivity and low density. However, poor impedance matching and high electrical conductivity limit their EMW absorption properties. Metal single atoms absorbers have garnered considerable attention in EMW absorption, largely due to the high metal availability and special coordination structure, but the modulation of the EMW absorption properties still needs to be improved. Herein, atomically dispersed Fe sites embedded into the N-doped mesoporous carbon spheres (Fe–SAs/NC) were synthesized through a facile coordination-assisted polymerization assembly strategy without acid leaching treatment. Benefitting from abundant mesoporous structure, the Fe–SAs/NC displays large specific surface area (339 m2 g−1) and optimized impedance matching, which results in an effective reduction of the absorber density. The homogeneously dispersed Fe single atoms (Fe–SAs) on the carbon skeleton lead to the improvement in conduction and dipole polarization losses of Fe–SAs/NC, which endows Fe–SAs/NC with exceptional EMW absorption properties. Experimental results indicate that Fe–SAs/NC displays desirable EMW absorption properties with the minimal reflection loss of −52.5 dB at 2.8 mm and the effective absorption bandwidth of 4.8 GHz. The study provides valuable insights for the development of carbon materials modified with atomically dispersed metal sites to achieve high-efficient EMW absorbers.

FeCo Alloy Nanoparticles Supported on N-doped Mesoporous Carbon Spheres for Hydrogen Evolution and Reduction of Organic Dyes

FeCo Alloy Nanoparticles Supported on N-doped Mesoporous Carbon Spheres for Hydrogen Evolution and Reduction of Organic Dyes

Enhanced stability in Co0.8Ni0.2/NDMCS catalysts: Carbon nitride encapsulation for robust hydrogen generation

Catalytic hydrolysis of NaBH4 is a promising method for "on-demand" hydrogen generation, with cobalt catalysts playing a key role due to their high hydrogen generation rates. However, rapid cobalt dissolution and poor recycling hinder stable hydrogen production. This study presents a dual-mode stabilization technique using carbon nitride encapsulation to address these challenges. Co0.8Ni0.2 alloy nanoparticles (NPs) are confined within N-doped mesoporous carbon spheres (NDMCS) and encapsulated with a carbon nitride shell (∼ 5 nm thick). XPS results reveal strong non-classical metal-support interaction, increasing activation energy from 38.82 to 44.6 kJ mol−1, which controls cobalt's reactivity, leading to excellent recycling efficiency (90 % retention of initial rate, no change in particle size) in high-concentration reactants (2 %NaBH4 + 2 %NaOH). The retention rate drops to 26.8 % without this stabilization due to rapid metal dissolution. This stability of Co0.8Ni0.2 alloy in alkaline conditions has significant practical implications for hydrogen generation and other electrochemical applications.

Exploring nitrogen doped mesoporous carbon spheres for superior microwave absorption

Mesoporous carbon materials hold significant promise for usage in microwave absorption due to their wide and unique advantages stemming from their mesoporous structure. This study synthesizes N-doped mesoporous carbon spheres (NMCs) by carbonizing mesoporous silica nanospheres (MSN). By controlling the annealing temperature, the resulting NMCs exhibit a significant increase in pore size. The exceptional microwave absorption capability of multifunctional carbon with a mesoporous structure result from its appropriate composition. The minimum reflection loss (RL) can reach −58.04 dB with a thickness of 3.3 mm, and the corresponding effective absorption bandwidth (EAB) reaches up to 8.19 GHz, outperforming the many previously documented microwave absorbing materials. The material's practical application potential was evaluated using computer simulation technology (CST), resulting in a simulated RCS value of 32.88 dBm2.The microwave absorption process of this material has been extensively studied and thoroughly described. Our study offers valuable guidance for developing and producing efficient microwave absorbers doped with nitrogen and possessing a unique mesoporous structure.

FeCo alloy nanoparticles supported on N-doped mesoporous carbon spheres for effective degradation of antibiotics and industrial dyes

Iron (Fe) is widely recognized for its effectiveness in the Fenton reaction and is commonly used in wastewater treatment. However, exploring other metals in similar Fenton-like reactions has been relatively limited. FeCo alloy nanoparticles (NPs), anchored on nitrogen-doped mesoporous carbon spheres (FeCo/NMCS), have been effectively synthesized and used as a Fenton-like catalyst in wastewater treatment under alkaline conditions. The NMCS exhibited spherical with an average diameter of 488.1 nm, while the FeCo alloy NPs, uniformly distributed over the NMCS, had an average diameter of 8.2 nm. The mesopores served as anchoring points for the NiCo alloy NPs, effectively preventing their possible agglomeration. The NMCS was composed of 3.91 wt% nitrogen. With 30 mg of FeCo/NMCS and 25 mM H2O2, more than 92% of tetracycline hydrochloride (TC) was degraded within 35 min at pH levels 7, 9, and 11. The remarkable degradation rate was attributed to the dual active sites present in the FeCo alloys. The rapid degradation of TC, even at pH 11, indicates the potential of FeCo/NMCS as a valuable solution for wastewater treatment under alkaline conditions. Industrial reactive (Y145, R195, B222A) and disperse dyes (O30, R167, B79) with a concentration of 10 ppm were degraded within 20 min when using 10 mg of the FeCo/NMCS catalyst and 25 mM H2O2 at pH 9. After five consecutive TC degradation cycles at pH 7 and 9, the FeCo/NMCS demonstrated consistent performance, emphasizing its reusability. FeCo/NMCS provides a promising solution to pollution control and wastewater treatment with stability, superior catalytic activity, magnetic separability, and recyclability.

Modulating the d-Band Center Enables Ultrafine Pt3 Fe Alloy Nanoparticles for pH-Universal Hydrogen Evolution Reaction.

By providing dual active sites to synergistically accelerate H2 O dissociation and H+ reduction, ordered intermetallic alloys usually show extraordinary performance for pH-universal hydrogen evolution reaction (HER). Herein, activated N-doped mesoporous carbon spheres supported intermetallic Pt3 Fe alloys (Pt3 Fe/NMCS-A), as a highly-efficient electrocatalyst for pH-universal HER, are reported. The Pt3 Fe/NMCS-A exhibits low overpotentials (η10 ) of 13, 29, and 48mV to deliver 10mAcm-2 in 0.5mH2 SO4 , 1.0mKOH, and 1.0m phosphate buffered solution (PBS), respectively, as well as robust stability to maintain the overall catalytic performances. Theoretical studies reveal that the strong Pt 5d-Fe 3d orbital electronic interactions negatively shift the d-band center (εd ) of Pt 5d orbital, resulting in reduced H* adsorption energy of Pt sites and enhanced acidic HER activity. With Pt and Fe acting as co-adsorption sites for H* and *OH intermediates, respectively, a low energy barrier is required for Pt3 Fe/NMCS-A to dissociate H2 O to afford H* intermediates, which greatly promotes the H* adsorption and H2 formation in alkaline and neutral conditions. The synthetic strategy is further extended to the synthesis of Pt3 Co and Pt3 Ni alloys with excellent HER activity in pH-universal electrolytes, demonstrating the great potential of these Pt-based alloys for practical applications.

Ru-Ni Alloy Nanoparticles Loaded on N-Doped Amphiphilic Mesoporous Hollow Carbon@silica Spheres as Catalyst for the Hydrogenation of α-Pinene to cis-Pinane.

N-doped mesoporous carbon spheres (NHMC@mSiO2 ) encapsulated in silica shells were prepared by emulsion polymerization and domain-limited carbonization using ethylenediamine as the nitrogen source, and Ru-Ni alloy catalysts were prepared for the hydrogenation of α-pinene in the aqueous phase. The internal cavities of this nanomaterial are lipophilic, enhancing mass transfer and enrichment of the reactants, and the hydrophilic silica shell enhances the dispersion of the catalyst in water. N-doping allows more catalytically active metal particles to be anchored to the amphiphilic carrier, enhancing its catalytic activity and stability. In addition, a synergistic effect between Ru and Ni significantly enhances the catalytic activity. The factors influencing the hydrogenation of α-pinene were investigated, and the optimum reaction conditions were determined to be as follows: 100 °C, 1.0 MPa H2 , 3 h. The high stability and recyclability of the Ru-Ni alloy catalyst were demonstrated through cycling experiments.

Sandwich-like hierarchical porous dual-carbon catalyst with more accessible sites for boosting oxygen reduction reaction

Fabricating highly efficient catalysts toward oxygen reduction reaction (ORR), especially carbon-based metal-free ones, plays a crucial role in large-scale applications of various renewable energy conversion devices. However, the poor electrocatalytic performance of these carbon catalysts severely hinders their application because most active sites are deeply buried inside the carbon framework and fail to be accessible for the reactants. In this work, we fabricate multimodally porous N-doped dual-carbon catalyst with a sandwich-like structure, that is, N-doped mesoporous carbon spheres loaded on reduced graphene oxide nanosheets (N-MCS@rGO). The obtained catalysts exhibit interconnected hierarchical microporous/mesoporous/macroporous structure and a high specific surface area, which can simultaneously maximize the efficient utilization of active sites and facilitate mass transport, resulting in superior alkaline ORR activities. The half-wave potential of the N-MCS@rGO was ~0.85 V vs. reversible hydrogen electrode (RHE) in 0.1 M KOH, preceding most of the non-noble metal catalysts and comparable with ~0.86 V vs. RHE of commercial 20 wt% Pt/C catalysts. The established Zn-air batteries using the N-MCS@rGO as the air cathode exhibit a high power density of 100 mW/cm2, outperforming the commercial Pt/C catalyst-based battery. This work supplies an interesting avenue in the rational construction of multidimensional hierarchically porous materials for advanced energy conversion technologies.

The extraction of four endocrine disrupters using hollow N-doped mesoporous carbon spheres with encapsulated magnetite (Fe3O4) nanoparticles coupled to HPLC-DAD determination

Magnetite/hollow core–shell N-doped mesoporous carbon sphere (Fe3O4/N-HCSCs) composites were prepared as a sorbent for ultrasound-assisted magnetic solid-phase extraction of four endocrine disrupter compounds (EDCs) from water samples prior to the EDCs determination by high-performance liquid chromatography with a diode array detector (HPLC-DAD) (analytical wavelength, 260 nm). The Fe3O4/N-HCSCs, which contained N-HCSCs with encapsulated magnetite nanoparticles, were also characterized. The extraction and elution conditions were optimized by a one-factor-at-a-time approach using prepared Fe3O4/N-HCSCs for the selected the EDCs (triclosan, triclocarban, bisphenol A, and tetrabromobisphenol A bis(allyl)ether). Under the optimum extraction/elution conditions, the previously mentioned procedure achieved low detection limits (0.05–0.1 μg·L−1), high recovery values (88.0%–97.0%), satisfactory preconcentration factors (115–136), and good reproducibility (relative standard deviations of less than 5.8%, n = 4). Kinetic and isotherm studies showed that the adsorption process followed pseudo-second-order kinetic and Freundlich equilibrium models. The Fe3O4/N-HCSCs had a good selectivity for the selected EDCs, mainly due to the large specific surface area of the sorbent, the presence of nitrogen species on the sorbent, and the hydrophobic interaction between the EDCs and sorbent. This work revealed the potential value of the method for rapidly screening EDCs in environmental water samples.

Conversion of CO2 into cyclic carbonate catalyzed by an N-doped mesoporous carbon catalyst

Ammonium hydroxide is first used as a nitrogen source to synthesize N-doped mesoporous carbon spheres (N-MCSs). Using N-MCS800 as a catalyst, the TOF of the cycloaddition of CO2 with epichlorohydrin is 236 h−1.

One-pot and surfactant-free synthesis of N-doped mesoporous carbon spheres for the sensitive and selective screening of small biomolecules

Abstract A facile electrochemical sensor based on the mesoporous N-doped carbon spheres (MNCS) was reported for the sensitive and selective screening of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The MNCS materials were prepared in a one-pot and surfactant-free synthesis method through the ethylenediamine-assisted cooperative self-assembly between 3-aminophenol/formaldehyde (APF) and silica templates. The resulted MNCS showed the high nitrogen content (8.21 at.%) and rich specific surface areas (up to 1149 m2 g−1). Benefited from the good properties of MNCS, the MNCS modified GC electrode (MNCS/GCE) exhibited high electrocatalytic activity towards AA, DA and UA with large peak potential separation and enhanced peak currents. Besides, MNCS/GCE displayed high sensitivity and good selectivity in the simultaneous detection of AA, DA and UA with low detection limits (S/N = 3) of 5.39 μM, 0.17 μM and 0.34 μM, respectively. Furthermore, MNCS/GCE possessed good stability and great anti-interference towards some common compounds in body fluid. Therefore, it was successfully applied to determine the three species in artificial urine samples. The attractive features of MNCS provided the potential applications of MNCS in sensing biomolecules.

Construction of NiCo2S4 heterostructure based on electrochemically exfoliated graphene for high-performance hybrid supercapacitor electrode

Bimetallic transition metal sulfides (TMSs) hold great promise as electrode materials for supercapacitive energy storage devices compared with their monometallic counterparts. However, it is still necessary to develop efficient synthetic protocols for favorable electrode architecture in order to further improve the electrochemical performance. This study presents a facile and controllable method to construct NiCo2S4 heterostructure based on electrochemically exfoliated graphene with good adhesion, which involves the growth of bimetallic MOF precursor and in-situ conversion into NiCo2S4 nanoparticles. This integrated architecture was found to be efficient for supercapacitive energy storage, as evident by the improved utilization of NiCo2S4 and excellent electrochemical performance including high capacity of 1802.5 F g−1 at 1 A g−1 and good rate capability (86.1% capacity retention at 10 A g−1). Additionally, N-doped mesoporous carbon spheres (NMCS) were synthesized by sacrificial template method and used as anode for practical application. Benefiting from good charge balance and compatibility, the assembled EEG@NiCo2S4//NMCS hybrid supercapacitor (HSC) exhibited outstanding energy density (30.4 Wh kg−1 at 800.0 W kg−1) and excellent cycling stability (80.1% capacitance retention after 9000 cycles).

Periodic Three-Dimensional Nitrogen-Doped Mesoporous Carbon Spheres Embedded with Co/Co3O4 Nanoparticles toward Microwave Absorption.

Although various bio-inspired materials with outstanding mechanical, acoustic, and optic properties have been developed, bio-inspired materials for microwave absorption applications are rarely reported. Herein, under the inspiration of the opal structure, for the first time, a kind of Co@Co3O4/nitrogen-doped (N-doped) mesoporous carbon sphere (Co@Co3O4/NMCS) with a periodic three-dimensional structure toward microwave absorption application was designed and synthesized. The microwave absorption performance was optimized with respect to the content of Co@Co3O4 nanoparticles. Co@Co3O4/NMCS with ∼20 wt % Co@Co3O4 achieves a reflection loss of -53.8 dB at 5.7 GHz. The simulated radar cross section demonstrated that the Co@Co3O4/NMCS can efficiently suppress the strong electromagnetic scattering from a metal groove structure, which further reveals its excellent absorbing performance. These periodic porous structures of N-doped mesoporous carbon spheres combined with the magnetic Co@Co3O4 nanoparticles contribute to the excellent microwave-absorbing performance.

Fe, N-doped carbon spheres prepared by electrospinning method as high efficiency oxygen reduction catalyst.

Electrocatalysts for the oxygen reduction reaction (ORR) are crucial in metal–air batteries, fuel cells and other electrochemical devices. In this study, iron and nitrogen co-doped carbon sphere electrocatalysts were synthesized by electrospinning and thermal treatment. According to the results, the catalyst marked as Fe–N/MCS-181 (Fe, N-doped mesoporous carbon spheres, iron nitrate nonahydrate as the iron source) has not only the highest iron content, which reaches up to 0.13%, but also a spherical shape. And its pore sizes are 11 and 35 nm. For the electrochemical performance, the onset potential (Eonset) of Fe–N/MCS-181 is −0.018 V, while the half-wave potential (E1/2) of Fe–N/MCS-181 is −0.145 V, which is better than the commercial Pt/C catalyst (E1/2 is −0.18 V). The durability of the Fe–N/MCS-181 catalyst is better than commercial Pt/C. After 10 000 s, the retention ratio of current density is 86.4%, while that of the commercial Pt/C catalyst is 84.2%. At the same time, the methanol tolerance of the Fe–N/MCS-181 catalyst is also excellent. After adding methanol, the current density of the Fe–N/MCS-181 catalyst has no obvious change. This study provides an easy method to fabricate a highly efficient and durable Fe, N-doped carbon catalyst for the oxygen reduction reaction.

Ionic liquid-induced tunable N-doped mesoporous carbon spheres for supercapacitors

N-Doped mesoporous carbon spheres with tunable structures have been prepared by a feasible co-assembly under the induction of an ionic liquid for supercapacitors.

Corrosion performance of carbon steel in N-doped mesoporous carbon spheres (NMCS)-containing alkaline medium in presence of chloride

The electrochemical response of carbon steel in chloride-free or chloride-containing 0.1 M and 0.9 M NaOH, in the presence of 0.016 wt.% NMCS, is the subject of this work. The NMCS exhibited a negative (in 0.1 M NaOH) and positive (in 0.9 M NaOH) zeta-potential. This determined altered steel electrochemical response, improved overall, especially in chloride-containing 0.9 M NaOH. The effect was related to an enhanced Fe3+ contribution in the passive film, when NMCS were present. The improved corrosion resistance was also attributable to a NMCS-triggered competition of OH− vs. Cl− ions in the medium, in other words, NMCS interference to promote passive layer stability.

Aging mechanism of MoS2 nanosheets confined in N-doped mesoporous carbon spheres for sodium-ion batteries

N-doped hollow carbon nanospheres (NHCS) with mesoporous carbon shells is selected as nanoreactors and encapsulated with few-layered MoS2 nanosheets to monitor its electrochemical properties and structural conversion in long-term cycling. Mesoporous walls of NHCS can facilitate electrolyte penetration and provide conductive shells for superior mass diffusion and charge transfer. When serving as SIB anodes, MoS2@NHCS has a capacity value of 371 mAh g-1 at 1 A g-1 with a capacity retention of 94.9% after 100 cycles which is higher than powder form MoS2 and is among the highest values of earlier reported MoS2 electrodes. The origin of gradual capacity decay of MoS2@NHCS anodes in-between 50 to 150 cycles has been investigated. Transmission electron microscopy and ex-situ X-ray diffraction have shown significant morphology change of space-confined MoS2 and the production of MoO3 together with oxygen-deficient MoOx after continuous charge/discharge test. After long-term cycle test of MoS2@NHCS, the ratios of Mo6+ and Mo5+ increased significantly with the decreasing of Mo4+ ratio, while the sulfur from MoS2 transformed from S2− to SO42−. This work highlight the phase transformation and composition change of MoS2 for MoS2-based anode in long-duration charge/discharge tests.

Material properties of cement paste and mortar, modified with N-doped mesoporous carbon spheres (NMCSs)

The addition of nitrogen doped mesoporous carbon spheres (NMCSs) to Portland cement-based materials was studied as an approach to produce materials of desired properties. Lower electrical resistivity and higher compressive strength were recorded in the presence of NMCSs, while the addition of a dispersion agent (Pluronic F127), caused an increase in electrical resistivity and strength reduction. This performance was related to the variation in zeta potential and hydrodynamic radius of NMCSs in alkaline medium. The zeta-potential of NMCSs was defined by the non-ionic surfactant F127. This led to a “poisoning” of the active NMCSs surface, consequently hindering the interaction of NMCSs with the cement-based material. Therefore, F127 is a non-suitable dispersing agent. In contrast, the presence of NMCSs alone enhances the desired cement-based materials properties, where reduced electrical resistivity and increased compressive strength were achieved, while cement hydration and pore network development were maintained close to NMCSs-free specimens.

Controlled Growth of N-Doped and Large Mesoporous Carbon Spheres with Adjustable Litchi-Like Surface and Particle Size as a Giant Guest Molecule Carrier.

N-doped mesoporous carbon nanospheres (NMCNs) with tunable particle size, pore size, surface roughness, and inner cavity are extremely important for the future development of new carriers for nanoencapsulation, high-performance giant molecule transport, and cell uptake. However, constructing such a multifunctional material via a simple method still remains a great challenge. Herein, a controlled growth technology was developed for the first time to synthesize such NMCNs based on the initial reaction temperature (IRT) and solution polarity. In this strategy, the IRT not only can adjust the micelle aggregation to obtain NMCNs with large mesopores but also can make the F127 micelle more lyophobic to prepare hollow N-doped mesoporous carbon spheres, which is a great breakthrough. Inspiringly, by varying the solution polarity to make nonuniform growth of nanoparticles, the litchi-like rough surface of NMCNs was obtained, which could significantly improve the cell uptake performance of NMCNs. The current understanding of nucleation and growth mechanism of nanospheres was further extended and realized the development of NMCNs with large mesopores and litchi-like rough surface, which provided a new and interesting fundamental principle for the synthesis of NMCNs. The mesoporous structure of NMCNs was successfully reverse-replicated by nanocasting of tetraethylorthosilicate to obtain mesoporous silica spheres (MSNs), revealing the easy transformation between NMCNs and MSNs. Insulin as a peptide drug cannot be directly administered orally. But it can be used as oral preparation after being loaded into NMCNs, which has never been reported before. Interestingly, the results of the animal experiment showed an excellent in vivo hypoglycemic activity. This finding provides a new paradigm for the fabrication of structurally well-defined NMCNs with a great promise for drug carriers.

N-doped mesoporous carbon spheres as the oxygen reduction reaction catalysts

The interest in the design and controlled fabrication of mesoporous carbon nanospheres emanates from their tremendous potential applications in adsorption, energy conversion and storage, gene therapy, and catalysis. Here, we report the synthesis of uniform N-doped mesoporous carbon spheres with tunable particle size from 40 to 750 nm by a one-pot soft template method. The synthetic method also allowed the preparation of N-doped microporous or mesoporous hollow carbon spheres. While all the resulting materials showed favourable electrocatalytic activity, the metal-free N-doped mesoporous hollow carbon spheres with particle size of ∼150 nm, in particular, exhibited the highest activity.