Nitrogen-doped Mesoporous Carbon Nanosheets Research Articles

Synthesis of metal-free nitrogen-doped mesoporous carbon nanosheets with reference to molecular self-assembly for efficient peroxymonosulfate activation

The application of metal-free carbon materials in Sulfate radical-based advanced oxidation processes (SR-AOPs) has attracted great attention. In SR-AOPs, porosity and active sites are the keys for nitrogen-doped carbon materials to exhibit high catalytic activity. In this paper, melamine and gallic acid were selected as raw materials, preparing metal-free nitrogen-doped carbon materials by using the molecular self-assembly synthesis method. The catalysts with different structural morphology and surface chemistry were obtained by controlling the pyrolysis temperature. It proposed the formation mechanism of nitrogen-doped mesoporous carbon nanosheets (NMC). The pyrolysis temperature was critical for the regulation of surface properties as well as the structure of carbon materials. It was found that NMC-800 exhibited fluffy and porous microstructure, and various active sites on the surface of the catalyst, including graphite N, pyridine N and CO. In the NMC-800/PMS system, the SMX degradation efficiency and corresponding rate constant could achieve 90.3 % and 0.1705 min−1, respectively. Besides, the degradation pathways and intermediate products of SMX were discussed by the analysis of quenching experiments, electron spin resonance (ESR) and liquid chromatography-mass spectrometry (LC-MS).

Sub-nanometric Manganous Oxide Clusters in Nitrogen Doped Mesoporous Carbon Nanosheets for High-Performance Lithium-Sulfur Batteries.

The greatest challenge for lithium-sulfur (Li-S) batteries application is the development of cathode hosts to address the low conductivity, huge volume change, and shuttling effect of sulfur or lithium polysulfides (LiPs). Herein, we demonstrate a composite host to circumvent these problems by confining sub-nanometric manganous oxide clusters (MOCs) in nitrogen doped mesoporous carbon nanosheets. The atomic structure of MOCs is well-characterized and optimized via the extended X-ray absorption fine structure analysis and density functional theory (DFT) calculations. Benefiting from the unique design, the assembled Li-S battery displays remarkable electrochemical performances including a high reversible capacity (990 mAh g-1 after 100 cycles at 0.2 A g-1) and a superior cycle life (60% retention over 250 cycles at 2 A g-1). Both the experimental results and DFT calculations demonstrate that the well-dispersed MOCs could significantly promote the chemisorption of LiPs, thus greatly improving the capacity and rate performance.

Phosphorus- and Nitrogen-Doped Carbon Nanosheets Constructed with Monolayered Mesoporous Architectures

Two-dimensional (2D) sandwich-structured phosphorus- and nitrogen-doped mesoporous carbon nanosheets have been synthesized by using graphene oxide (GO) as the substrate, triblock copolymer F127 mic...

Synthesis of nitrogen-doped mesoporous carbon nanosheets for oxygen reduction electrocatalytic activity enhancement in acid and alkaline media

In the present work, nitrogen-doped mesoporous carbon nanosheets (NMCNs) are prepared and extensively investigated for the oxygen reduction reaction. Initially, by using dual templates, viz. graphene oxide and a cationic surfactant, silica films (thickness: 1.0 nm) are synthesized and characterized using transmission electron microscope (TEM), nitrogen adsorption-desorption (N2 ad/des) measurements, and small-angle X-ray diffraction (SA-XRD).Morphology and structure of silica evolve along with graphene oxide concentration, while the co-operative assembly and the final structure are determined by the electrostatic interaction between the dual templates. The effect of silica template on the resultant NMCNs is investigated physicochemically by photoelectron spectroscopy (XPS), TEM, N2 ad/des and electrochemically by cyclic voltammetry (CV), and linear sweep voltammetry (LSV).NMCNs are featured of a high content of nitrogen dopant, high specific surface area (SSA) and ultrathin thickness (1.5 nm), favoring catalysis and facilitating the mass transport of the reactive species. From the electrochemical tests, it is confirmed that NMCNs yield a high oxygen reduction reaction (ORR) electrocatalytic activity in acid and alkaline environment; this activity is similar or even better as compared with the one measured over carbon supported platinum commercial catalyst (40 wt % Pt/C).

Microporous MOFs Engaged in the Formation of Nitrogen-Doped Mesoporous Carbon Nanosheets for High-Rate Supercapacitors.

Nitrogen-doped mesoporous carbon nanosheets (NMCS) have been fabricated from zinc-based microporous metal-organic frameworks (ZIF-8) by pyrolysis in a molten salt medium. The as-prepared NMCS exhibit significantly improved specific capacitance (NMCS-8: 232 F g-1 at 0.5 A g-1 ) and capacitance retention ratio (75.9 % at 50 A g-1 ) compared with the micropore-dominant nitrogen-doped porous carbon polyhedrons (NPCP-5: 178 F g-1 at 0.5 A g-1 , 15.9 % at 20 A g-1 ) obtained by direct pyrolysis of nanocrystalline ZIF-8. The excellent capacitive performance and high rate performance of the NMCS can be attributed to their unique combination of structure and composition, that is, the two-dimensional and hierarchically porous structure provides a short ion-transport pathway and facilitates the supply of electrolyte ions, and the nitrogen-doped polar surface improves the interface wettability when used as an electrode.

Nitrogen-doped mesoporous carbon nanosheets derived from metal-organic frameworks in a molten salt medium for efficient desulfurization

In this work, we report a novel synthesis of two-dimensional (2D) N-doped mesoporous carbon nanosheets (NMCS) with high nitrogen content and developed porosity from microporous Zn-based zeolitic imidazolate framework (ZIF-8) polyhedrons in a molten salt medium. The ZIF precursors allow high nitrogen content of the NMCS while the molten salt medium leads to the formation of 2D nanosheets with mesoporosity during the pyrolysis process. The obtained NMCS exhibit highly catalytic activity in the metal-free catalytic oxidation of H2S toward elemental sulfur at room temperature, high breakthrough sulfur capacity is achieved over NMCS, much superior to that of ZIF-8 derived N-doped porous carbons obtained by direct pyrolysis. The transformation of three-dimensional ZIF-8 into nitrogen-doped 2D carbon nanosheets via molten salt media has great potential for the large-scale and green production of porous carbon nanosheets for highly efficient desulfurization and energy storage-conversion.

Bottom-up fabrication of nitrogen-doped mesoporous carbon nanosheets as high performance oxygen reduction catalysts

Nitrogen-doped mesoporous carbon nanosheets (NMCNs) with uniform hexagonal structures are fabricated via the thermal treatment of polyaniline enwrapped cobalt hydroxide (Co(OH)2) nanosheets and the subsequent acid etching of the resulting composites. It is found that the morphologies, poroisties and compositions of the NMCNs are greatly dependent on the ratio of the added aniline and Co(OH)2 nanosheets, which can in turn affect the electrochemical behavior of the NMCNs. As the electrocatalyst for oxygen reduction reaction in alkaline media, the NMCNs obtained with the aniline/Co(OH)2 ratio of ∼1.2 manifest excellent perfromance with the onset potential of −0.119V, the half-wave potential of −0.182V and the limiting current density of 5.06mAcm−2, which are superior to most of the previously reported N-doped porous carbon nanosheets.

Nitrogen-doped mesoporous carbon nanosheets from coal tar as high performance anode materials for lithium ion batteries

Nitrogen-doped mesoporous carbon nanosheets from coal tar as high performance anode materials for lithium ion batteries

Nitrogen-doped mesoporous carbon nanosheets from coal tar as high performance anode materials for lithium ion batteries

Nitrogen-doped mesoporous carbon nanosheets (NMCNs) were prepared from coal tar and melamine using a layered MgO as template. Porous structures and nitrogen doping levels were readily tuned by adjusting experimental parameters. NMCNs show high specific capacities and excellent cyclic stabilities as anode materials for lithium ion batteries. A sample prepared under optimum conditions shows a high reversible capacity of nearly 1 000 mAh/g at a current density of 100 mA/g, which can be ascribed to its unique mesoporous sheet-structure, a high specific surface area of 1 209 m2/g, and a uniform and high bulk nitrogen content of 8.6%. Our work demonstrates that coal tar can act as an excellent carbon source for the production of carbon materials with high performance in lithium-ion batteries.