Mass production of highly fluorescent full color carbon dots from the petroleum coke

Heavy oil is treated as an undesirable raw material in traditional refining markets because of its low yield. However, its rich natural aromatic structure and heteroatomic compounds make it possible to be a precursor to large-scale production of carbon materials. Using heavy oil and three SDA products as precursors, we synthesized highly fluorescent multi-color carbon dots (CDs) by hydrothermal method, which can precisely control the photoluminescence wavelength in the range of 350?650 nm. The synthesized carbon dots have the advantages of good long-term stability and stability under extreme pH conditions and low price. Importantly, the carbon dots synthesized with asphalt as the precursor have the highest fluorescence quantum yield. X-ray photoelectron spectroscopy (XPS) is used to elucidate the effects of different precursor on emission color change and photoluminescence quantum yield (PLQY), thus providing a controlled tuning of the system for the functionalization of CDs. And we further used the CDs in macrophage labeling. This pathway gives a reliable and repeatable industry possibility and may boost the applications of CDs into reality.     

Synthesis of N-Doped meso-macroporous carbon and its application to SO2 absorption

N-Doped meso-macroporous carbon materials were synthesized using melamine-formaldehyde resin as carbon precursor and silica spheres as a removable template. The as-synthesized carbon materials with a bimodal pores structure (about 3.9 and ～50–200 nm) display a high surface nitrogen content of 30 wt %. The macropores of carbon materials can be modulated by changing the diameter of template. The SO₂ adsorption experiments demonstrate a high adsorption capacity of 78.6 mg g^?1 and a considerable stability even over 9 cycles for the carbon materials.     

From metal-organic framework to nanoporous carbon: toward a very high surface area and hydrogen uptake

In this work, with a zeolite-type metal-organic framework as both a precursor and a template and furfuryl alcohol as a second precursor, nanoporous carbon material has been prepared with an unexpectedly high surface area (3405 m(2)/g, BET method) and considerable hydrogen storage capacity (2.77 wt % at 77 K and 1 atm) as well as good electrochemical properties as an electrode material for electric double layer capacitors. The pore structure and surface area of the resultant carbon materials can be tuned simply by changing the calcination temperature.     

From triazines to heptazines: deciphering the local structure of amorphous nitrogen-rich carbon nitride materials

Nitrogen-rich carbon nitride (CN x , x >/= 1) network materials have been produced as disordered structures by a variety of precursor-based methods, many that involve solid-state thermolysis at or above 500 degrees C. One popular precursor building block is the triazine unit (C 3N 3), and most postulated amorphous CN x network structures are based on cross-linked triazine units. Since hydrogen is most often observed in the product, these materials are usually more appropriately described as CN x H y materials. Results from recent carbon nitride studies using larger conjugated heptazine (C 6N 7) precursors and from rigorous structural investigations of triazine to heptazine thermal conversion processes have prompted a reexamination of likely local structures present in amorphous carbon nitride networks formed by triazine thermolysis reactions. In the present study, the formation and local structure of a CN x H y material formed via the rapid and exothermic decomposition of a reactive triazine precursor, C 3N 3(NHCl) 3, was examined by byproduct gas mass spectrometry, NMR and IR spectroscopy, base hydrolysis, and crystallographic analysis. The combined results clearly indicate that the moderate-temperature ( approximately 400 degrees C) self-sustaining decomposition of trichloromelamine results in ring fragmentation and reorganization into a CN x H y product that contains predominantly larger heptazine-like structural building blocks. These results may have applicability to many other disordered carbon nitride materials that are formed via triazine thermolysis. It also provides clearer and more accurate structural guidance in the use of these carbon nitrides as photoactive materials or coordination supports for metal and nonmetal species.     

Upper Limit of Nitrogen Content in Carbon Materials

Nitrogen‐doped carbon materials (NDCs) play an important role in various fields. A great deal of effort has been devoted to obtaining carbon materials with a high nitrogen content; however, much is still unknown about the structure of the nitrogen‐doped materials and the maximum nitrogen content possible for such compounds. Here, we demonstrate an interesting relationship between the N/C molar ratio and the N content of NDCs. The upper limit for the nitrogen content of NDCs that might be achieved was estimated and found to strongly depend on the carbonization temperature (14.32 wt % at 1000 °C and 21.66 wt % at 900 °C), irrespective of the precursor or preparation conditions. Simulations suggest that, especially in the carbon architectures obtained at high temperatures, nitrogen atoms are always located on separate hexagon moieties in a graphitic configuration, thereby yielding a critical N/C molar ratio very close to the value estimated from the experimental results.     

基于不同前驱体制备的硬碳负极材料的储锂性能

以聚丙烯腈、石油沥青和花生壳为前驱体,在1200℃下碳化制备三种不同的硬碳材料。通过扫描电子显微、X射线衍射、氮气吸附/脱附测试和拉曼光谱等方法探究不同前驱体所制备的硬碳材料的表面形貌和物相结构。通过恒流充放电测试考察了这三种硬碳负极材料的电化学性能。结果表明,花生壳基硬碳的初始放电比容量最高,但首圈库仑效率最低,石油沥青基硬碳的首圈库仑效率最高但是比容量最低,聚丙烯腈基硬碳具有较高的循环比容量和稳定性。     

The recent progress of pitch-based carbon anodes in sodium-ion batteries

Sodium-ion batteries(SIBs)have attracted significant attentions as promising alternatives to lithium-ion batteries for large-scale energy storage applications.Here carbon materials are considered as the most competitive anodes for SIBs based on their low-cost,abundant availability and excellent structural stability.Pitch,with high carbon content and low cost,is an ideal raw precursor to prepare carbon materials for large-scale applications.Nevertheless,the microstructures of pitch-based carbon are highly ordered with smaller interlayer distances,which are unfavorable for Na ion storage.Many efforts have been made to improve the sodium storage performance of pitch-based carbon materials.This review summarizes the recent progress about the application of pitch-based carbons for SIBs anodes in the context of carbon’s morphology and structure regulation strategies,including morphology adjustment,heteroatoms doping,fabricating heterostructures,and the increase of the degree of disorder.Besides,the advantages,present challenges,and possible solutions to current issues in pitch-based carbon anode are discussed,with the highlight of future research directions.This review will provide a deep insight into the development of low-cost and high-performance pitch-based carbon anode for SIBs.     

Surface characteristics of activated carbons obtained by pyrolysis of plasma pretreated PET

Activated carbon materials have been prepared by pyrolysis of plasma pretreated recycled PET. The obtained carbon materials have been texturally characterized by N2 (77 K) and CO2 (273 K) adsorption. Atomic force microscopy (AFM) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) have been used to analyze the surface of the treated precursors. Carbon materials obtained by He, N2, and CO2 plasma pretreatments (4 min) of the precursor and subsequent pyrolysis have shown a higher adsorption capacity than the corresponding chars (untreated pyrolised PET). This effect seems to be related to the elimination by the plasma treatments of low-molecular-weight products in the precursor, which are responsible for the formation of amorphous carbon deposits during the carbonization that blocks the porosity. Longer periods of treatment (15 min) do not favor the opening of the microporosity because cross-linking reactions in the precursor producing high molecular weight deposits prevail. The development of porosity is less relevant if oxygen plasma is used, as a considerable amount of oxygen functionalities are also formed. These groups can decompose during pyrolysation producing the above-mentioned amorphous carbon deposits. The textural characteristics of the carbon materials obtained after 4 min of plasma treatment on the precursor are very similar to those obtained after 4 h of CO2 (1073 K) activation of the same char. Therefore, this method can be an alternative to avoid the burnoff and high energy cost of the activation step.     

基于聚多巴胺的氮掺杂碳材料的制备及其电化学性能

多孔碳材料由于高的比表面积、优异的电子传导率、良好的化学稳定性等优点在超级电容器电极材料领域被广泛研究。 碳材料的组成及表面孔结构直接影响其电化学性能,为进一步提高碳材料的电容性能,本文首次以聚多巴胺球为前体,KOH为活化剂,通过高温碳化成功制备了良好电化学性能的氮掺杂多孔碳材料。 通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、 X射线粉末衍射(XRD)、傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)和Raman光谱等对所制备的氮掺杂多孔碳材料进行了形貌及结构组成的表征。 在6 mol/L KOH电解液中, 采用循环伏安、恒电流充放电对多孔碳材料的电化学性能进行了研究。 结果表明,由于双电层电容和赝电容的协同作用,在电流密度为1 A/g时,材料的比电容可达269 F/g,充放电循环1000圈后电容仍可保留初始值的93.5%。     

Modulating the Acidic and Basic Site Concentration of Metal-Organic Framework Derivatives to Promote the Carbon Dioxide Epoxidation Reaction

Metal-organic framework (MOF) is an ideal precursor/template for porous carbon, and its active components are uniformly doped, which can be used in energy storage and catalytic conversion fields. Metal-organic framework PCN-224 with carboxylporphyrin as the ligand was synthesized, and then Zn²⁺ and Co²⁺ ions were coordinated in the center of the porphyrin ring by post-modification. Here, PCN-224−ZnCo with different ratios of bimetallic Zn²⁺/Co²⁺ ions were used as the precursor, and the metal-nitrogen-carbon(M−N−C) material of PCN-224−ZnCo-950 was obtained by pyrolyzing the precursor at 950 °C in Ar. Because Zn is easy to volatilize at 950 °C, the formed M−N−C materials can reflect different Co contents and different basic site concentrations. The formed material still maintains the original basic framework. With the increase of Zn²⁺/Co²⁺ ratio in precursor, the concentration of N-containing alkaline sites in pyrolysis products gradually increase. Compared with the precursor, PCN-224−ZnCo₁-950 with Zn²⁺/Co²⁺=1 : 1 has greatly improved basicity and suitable acidic/ alkaline site concentration. It can be efficiently used to carbon dioxide absorption and catalyze the cycloaddition of CO₂ with epoxide. More importantly, the current method of adjusting the acidic/basic sites in M−N−C materials through volatilization of volatile metals can provide an effective strategy for adjusting the catalysis of MOF derivatives with porphyrin structure.