Preparation Of Carbon Spheres Research Articles

LiBr hydrate as reaction medium for preparation of carbon spheres from wood powders via hydrothermal carbonization

In this work, a suitable solvent (Lithium Bromide Hydrate) was selected and used for the efficient dissolution and carbonization of biomass for the preparation of carbon spheres directly from wood powders by hydrothermal carbonization (HTC), which was so far the first successful attempt of making carbon spheres directly from woody biomass. The impacts of the preparation conditions on the yield and morphology of carbon spheres were carefully studied, and it was found that the yield and degree of carbonization of carbon spheres were positively correlated with the temperature and reaction time. The optimal operation conditions were determined as 170 °C, reaction time 5 h and LiBr concentration 65 wt%. And the produced carbon spheres have an average particle size of 603 nm with a yield of 22.4%. The characterization of carbon spheres revealed that the prepared nanoparticles had excellent spherical morphology and multifunctional groups, which led to a better surface reactivity than the raw material itself. Moreover, levulinic acid (LA) and 5-hydroxymethylfurfural (5-HMF) were found in the liquid phase of the reaction products, indicating the furan derivatives were formed in the HTC process, which demonstrated a great potential of biomass valorisation with this innovative process.

Polyol assisted formaldehyde reduction of bi-metallic Pt-Pd supported agro-waste derived carbon spheres as an efficient electrocatalyst for formic acid and ethylene glycol oxidation

This report explains, (i) the preparation of carbon spheres (CS) from agro-waste through hydrothermal carbonization (HTC) followed by high temperature carbonization, (ii) the decoration of bi-metallic Pt-Pd nanoparticles (Pt-Pd NPs) with different compositions (Pt/C, Pt0.5Pd1/C, Pt1Pd1/C and Pt1Pd0.5/C, Pd/C) on the carbon by ethylene glycol solvated polyol assisted formaldehyde reduction method and (iii) subsequently used as the electrocatalyst for formic acid (FA) and ethylene glycol (EG) electro-oxidation. The structural and morphological properties of the electrocatalysts were studied using advanced physicochemical characterization techniques. The obtained results well evidence the homogeneous dispersion of Pt-Pd NPs on the surface of the carbon. Especially, Pt0.5Pd1/C exhibited excellent electrocatalytic property towards formic acid electro-oxidation reaction (FAOR) with a higher current density (256 mA cm−2) and stability due to “third body effect”. On the other hand, Pt1Pd0.5/C expressed superior electrochemical performance towards ethylene glycol electro-oxidation reaction (EGOR) due to the strong interaction between high Pt content and Pd. Hence, this work reveals the improved electrocatalytic performance of bi-metallic Pt-Pd NPs supported biomass-derived carbon as a promising anodic electrocatalyst towards FAOR and EGOR.

Fast preparation of carbon spheres from enzymatic hydrolysis lignin: Effects of hydrothermal carbonization conditions

This study explores the effect of carbon sphere preparation conditions on the morphology of the carbon spheres and the micropore development by fast potassium hydroxide activation via microwave heating. Enzymatic hydrolysis lignin is used as the precursor for carbon sphere preparation via environmentally friendly hydrothermal carbonization. The effects of various carbonization temperatures, carbonization times and reaction concentrations on the physical morphology of the carbon sphere surfaces are investigated. The Brunauer-Emmett-Teller surface area, yield and scanning electron microscopic images are used to characterize the carbon spheres. High carbonization temperatures and times result in large particle sizes, high sphericity, uniform size, and high dispersity of the carbon spheres. The best carbon spheres are obtained at 270 °C for 7 hours with a reaction concentration of 0.06 g ml−1 and a particle size of 3–6 μm. After activation, the Brunauer-Emmett-Teller surface area of the activated carbon spheres increases from 248 m2 g−1 to 1278 m2 g−1. Carbon spheres activated by treatment with fast potassium hydroxide and microwave heating can develop micropores that enhance the adsorptive capacity for small molecules, such as gases. Enzymatic hydrolysis lignin-derived carbon spheres formed via hydrothermal carbonization should be potentially sustainable materials applicable in energy and environmental fields.

Facile preparation of carbon sphere supported molybdenum compounds (P, C and S) as hydrogen evolution electrocatalysts in acid and alkaline electrolytes

Efficient electrocatalysts for hydrogen evolution reaction (HER) were developed based on the homogeneous dispersion of molybdenum composites (MoP, Mo2C, MoS2) on a glucose- derived carbon sphere matrix obtained by simply changing the precursors during the high temperature treatment. The potential composite materials showed different performance characteristics in different experimental designs. The as-synthesized MoP showed the best HER performance in acid medium with a low overpotential of 136mV obtained at 10mAcm−2, while Mo2C-C showed the lowest overpotential for HER in alkaline medium, and for MoS2-C, which exhibited few layers structure (less than three layers), exhibiting favorable catalytic performance in both acid and alkaline electrolytes. Both MoP-C and Mo2C-C showed negligible overpotential loss after 5000 cycles in acid medium, but were relative unstable in alkaline medium. Moreover, the carbon sphere matrix improved the catalytic performance of molybdenum compounds by alleviating the aggregation of catalysts, providing sufficient area for electrolyte contact, and facilitating electron transfer. This work demonstrates a facile avenue to prepare cost-effective molybdenum compounds for HER. Furthermore, electrochemical performance of the catalysts was investigated in both acid and basic media.

Preparation of Pt/Carbon-Sphere As Cathode Catalyst of PEFC

Polymer electrolyte fuel cell (PEFC) is emerged as one of the candidates for automotive and residential power sources because has relatively small and lightweight and works under 100ºC. The electrocatalyst of PEFC consists of platinum nanoparticles, which size is several nanometers, and activated carbon as catalyst support. Catalyst support requires to two things at least; one is good electron conductivity, second one is high surface area in order to achieve dispersing of platinum particles. Activated carbon is cheap and meets two requirements needed as catalyst support. Therefore, activated carbon is widely used as catalyst support in PEFC. However, activated carbon is corroded under the start-up/shutdown conditions reaching the high potential region. Carbon corrosion leads to detachment and aggregation of platinum nanoparticles. These phenomena mean catalyst degradation, and are directly linked to decrease of cell performance. In addition, platinum utilization is not high in case of using activated carbon as catalyst support. This attributes that platinum nanoparticles is accommodated by complex pore structure of activated carbon. For realization of wide-spread commercialization of PEFC, inhibition of catalyst degradation and improvement of platinum utilization are necessary to build up the low cost system. Recently, graphitization carbon is focused as corrosive-resistant carbon support. Graphene, in particular, has high stability of thermodynamics and good electron conductivity. We succeeded already a preparation of carbon sphere composed from graphite oxide nanosheets (GOns) wall. GOns could reduce by the reductant, such as hydrazine and hydrogen, and is given electron conductivity by reduction treatments. Moreover, our carbon sphere is expected to decrease the substance diffusion resistance of oxygen and water, due to it has homogeneous size. In this study, platinum nanoparticles supported on carbon sphere, and its activity of oxygen reduction reaction and durability were evaluated. Graphite oxide was synthesized by typical Hummers method. GOns colloid solution was obtained by shaking GO with 0.01 wt% TBAOH aqueous solution. Preparation method of carbon sphere was briefly described below. Polymer spheres were dispersed in cationic polymer aqueous solution and washed with ultrapure water. After that, their polymer spheres were mixed with GOns colloid solution. The above procedure was repeated five times. Platinum supported carbon sphere was prepared by a traditional impregnation method. Platinum hexahydrate ethanol solution was added to a carbon sphere dispersed with ethanol. And then, this mixed solution was dried at 60ºC. A dried powder containing platinum complex was reduced at 200ºC under the vacuum conditions. Its morphology and crystalline structure were observed SEM and XRD, raman spectroscopy. Electrochemical measurement was conducted by rotating disk electrode method. A working electrode was prepared by thin film method. Briefly, test catalyst was dispersed in mixed solution of ultrapure water and isopropyl alcohol. And then catalyst dispersion solution was dropped 10 µL on the mirror-polished glassy carbon electrode and dried at 60°C. Carbon sphere as catalyst support was kept sphere shape after platinum deposition treatments. This platinum supported catalyst may form by stacked GOns wall and polymer sphere core. Because raman peaks attributed polymer sphere were not observed, but D- and G-band attributed GOns were observed. In diffraction peaks of XRD, clear peaks were observed at ~40° and ~45°. These diffraction peaks are attributed to Pt (111) and Pt (200) phases. On the other hand, diffraction peaks of polymer sphere were not observed. In addition, oxygen reduction activity and hydrogen adsorption/desorption current of platinum were also confirm by electrochemical measurement using rotating disk electrode method. Thus, we succeeded synthesis of platinum supported carbon sphere catalyst as new electrocatalyst. Its activity of oxygen reduction reaction and durability will be reported at the venue.

Preparation of carbon spheres supported CdS photocatalyst for enhancement its photocatalytic H2 evolution

In this work, we prepare a series of carbon spheres (CSs) supported CdS photocatalyst via simple co-precipitation combined aging method towards the photocatalytic hydrogen production under visible light irradiation. The synthesized photocatalysts are characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, Nitrogen adsorption–desorption measurement, scanning electron microscopy (SEM) and so on. The UV–vis diffuse reflectance spectroscopy shows that all of the CSs/CdS samples can respond more visible-light than pure CdS. The SEM and TEM images demonstrate that the 1% CSs/CdS sample have less aggregation than pure CdS, which can provide more reactive sites and benefit the photocatalytic reaction. The results of photocatalytic experiments prove that the CSs/CdS composites exhibit a significantly enhanced photocatalytic activity for H2 production compared with pure CdS under visible light irradiation. Especially for the 1% CSs/CdS sample, the average H2-production rate reaches 583μmol/h, nearly 1.8 times than that of pure CdS. The enhanced photocatalytic activity of the CSs/CdS composites can be attributed to the large surface area of CSs/CdS samples and good electroconductivity of CSs, which can effectively separate the photo-generated electron-hole pairs of CdS. This method effectively improves the photocatalytic activity of CdS. In addition, the possible photocatalytic mechanism of CSs/CdS composites for H2 evolution is proposed.

Synthesis and magnetic properties of highly dispersed tantalum carbide nanoparticles decorated on carbon spheres

The decoration of carbon spheres (CS) by highly dispersed tantalum carbide nanoparticles (TaC NPs) was achieved, for the first time by a unique carbothermal reduction method at 1350 °C for 30 min under reduced oxygen partial pressure. TaC NPs decorated CS composites were then extensively characterized by powder X-ray diffraction and electron microscopy techniques. The composite spheres were approximately 0.8–1 μm in diameter with an average size of 41 nm for the TaC NPs located at the surface. Transmission electron microscopy and Raman analysis showed the formation of the graphene layer at the outer surface of the TaC NPs. An anomalous ferromagnetic response with a spin-glass like behavior has been observed at low temperature in the dc magnetization study with complete suppression of the superconducting response. For ease of synthesis and high reproducibility, this technique opens a new paradigm in the preparation of carbon sphere supported high melting metal carbide nanoparticles for various technological purposes.

Hierarchically tunable porous carbon spheres derived from larch sawdust and application for efficiently removing Cr (Ⅲ) and Pb (Ⅱ)

Waste larch sawdust was used as a starting material for the preparation of carbon spheres with tunable morphologies and porous structures using successive steps liquefaction, resinification, self-assembly, carbonization, and KOH activation. Owing to the evaporation-induced self-assembly (EISA) of soft template (F127) in the presence of larch resin precursor under hydrothermal conditions, spherical particles were formed. The carbon spheres were uniform and possessed a hierarchically micro-mesoporous structure. Mesopores were generated upon decomposition of F127 and micropores were formed upon KOH activation. The diameter of the carbon spheres was in the range of 10–25 μm, and the vermicular pore size of the carbon spheres had a range of 2.0–5.0 nm (mesopores) and 1.5–2.0 nm (micropores). The carbon spheres had a high surface area of 1064 m2/g and a large pore volume of 0.503 cm3/g. The adsorption capacities of hierarchically carbon sphere for removal were 70% and 90% for Cr (Ⅲ) and Pb (Ⅱ), respectively.

Comparative Study of Textural Characteristics on Methane Adsorption for Carbon Spheres Produced by CO2Activation

Resorcinol-formaldehyde resin polymer was used as raw material for preparation of carbon spheres. Samples were treated with CO2flow at 850°C by varying activation times. The CO2activation granted better pore development of pore structure. The experimental data of CH4adsorption as a function of equilibrium pressure was fitted by Langmuir and Dubinin-Astakhov (D-A) models. It was concluded that the high surface area and micropore volume of carbon spheres did unequivocally determine methane capacities. In addition, a thermodynamic study of the heat of adsorption of CH4on the carbon spheres was carried out. Adsorption of CH4on carbon spheres showed a decrease in the adsorption heat with CH4occupancy, and the heat of adsorption fell from 20.51 to 12.50 kJ/mol at 298 K and then increased to a little higher values at a very high loading (>0.70), indicating that CH4/CH4interactions within the adsorption layer became significant.

Sonochemical preparation of carbon spheres

Spherical morphology of carbon with 150–400nm size is produced by sonication (480kHz, 2.5W) of toluene with water under ambient conditions. Medium range of frequency and weak power of ultrasound is found to be the appropriate conditions for preparing the carbon spheres. Morphological and structural analysis of the product is carried out with TEM, SEM, elemental analysis, TGA, and FT-IR spectroscopy.

Preparation of carbon sphere from lactose by hydrothermal reaction and its performance in gas separation

Carbon spheres were produced from mild hydrothermal reaction of biomass lactose, followed by carbonization with low‐activation temperatures (400°C). The Brunauer‐Emmett‐Teller (BET)‐specific surface area of carbon at optimum condition was 403 m2/g. The resultant carbon shows good performance in preferential adsorption of CO2 to CH4 below 50 kPa at 293 K. The results of the isosteric enthalpies of adsorption for different gases on prepared carbon indicate mildly heterogeneous surfaces. The relatively good performance of the resultant carbon in kinetics indicates its potential for low‐pressure kinetic separation of carbon dioxide from carbon dioxide and methane mixture at room temperature.. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 581–587, 2014

Preparation of carbon spheres from potato starch and its stabilization mechanism

Preparation of carbon spheres from potato starch and its stabilization mechanism

Preparation of carbon spheres from potato starch and its stabilization mechanism

Carbon spheres perfectly retaining the original morphology of potato starch were prepared by a two-step process including stabilization and carbonization. The potato starch was first stabilized at 210 °C under air, and the stabilized samples were then carbonized at 600 °C for 1h under N 2 atmosphere. In the process, stabilization treatment was the main step. The mechanism of stabilization was investigated by thermogravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and differential scanning calorimetry, and the morphology of the carbon spheres was characterized by scanning electron microscopy (SEM). Results show that during stabilization, the loss of water and the occurrence of decomposition and condensation reactions result in the destruction of the crystallite structure in the original potato starch. Thus, during the carbonization step, further intermolecular cross-linking makes microcrystalline melting very difficult. This promotes the formation of monodispersed carbon spheres. The SEM results show that only if the potato starch undergoes adequate stabilization treatment (e.g., 12 h) before carbonization, can the carbon spheres perfectly retain the original shape of the potato starch.

Preparation of carbon spheres by low-temperature pyrolysis of cyclic hydrocarbons

Low-temperature pyrolytic decomposition of xylene, benzene, toluene, and naphthalene was investigated as a low-cost method for synthesis of a large quantity of perfectly shaped pure carbon spheres. The reaction occurred in a closed iron container at temperatures in the range of 500–700 °C and under pressure of 20 MPa. Some of the experiments were carried out in the presence of distilled water in vapor state near to its critical point, under which conditions it reacted as a very strong oxidant. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis were used to investigate the properties of the material obtained. The results demonstrated that synthesis had proceeded in the following sequence: vaporization of hydrocarbon, hydrocarbon transformation to condensing drops of heavy hydrocarbons, then drop growth accompanied by continuous alteration of the heavy carbon compounds until their final carbonization. Synthesis in a closed space stimulated particle growth, and particle diameters reached 1 to 12 μm. Continuous condensation of vapor onto the resulting drops caused agglomeration of some of the spheres to form pearl-necklace-like chains when the spheres docked to one another in the course of growth. Carbon atoms in the spheres were arranged in concentric, incompletely closed graphitic shells, which made them stable up to 600 °C in air. Above this temperature, rapid sphere degeneration occurred. Oxygen reacted with carbon atoms situated at the shell edges during heating in air, with some remaining in the spheres; oxygen penetration increased with treatment temperature.

Synthesis and electrochemical characterization of carbon spheres as anode material for lithium-ion battery

Carbon spheres were synthesized by the thermal decomposition of RF precursor which was synthesized by surfactant-assisted polycondensation of resorcinol with formaldehyde. The morphology of precursor was preserved during the decomposition process. EDS, TG, SEM, CV and galvanostatic charge–discharge methods are used to characterize the composition, morphology, and electrochemical performance of carbon spheres. The results revealed that these carbon spheres had a spherical morphology, smooth surface and probable size of about 400 nm. When the carbon spheres were used as anode materials for lithium-ion battery, they exhibited a high lithium storage capacity and good cycle performance. In addition, the possible progress for the preparation of carbon spheres was proposed.

A novel method for preparation of hollow and solid carbon spheres

Hollow and solid carbon spheres were prepared by the reaction of ferrocene and ammonium carbonate in a sealed quartz tube at 500°C. The morphology and microstructure of the product were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The carbon spheres are amorphous and their diameters range from 0·8–2·8 μm. The shell thickness of the hollow carbon spheres is not uniform and ranges from 100–180 nm. It is suggested that ammonium carbonate is crucial for the formation of carbon spheres and its amount also influences the morphology of the product. The method may be suitable for large scale preparation of carbon spheres.

Preparation of carbon sphere from corn starch by a simple method

Carbon spheres with a regular and perfect shape was successfully synthesized from corn starch by a two stage process: oxidation and carbonization. In this process, oxidation treatment was the main step; the optimal oxidation temperature was 210 °C. The resulting products were characterized by using combined techniques including X-ray powder diffractometer (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The results showed that the products could keep the original shape of corn starch perfectly, and the diameters of carbon spheres ranged from 5 to 25 μm. It showed characteristic structure of non-graphitizing carbons heated at high temperatures. The preparation mechanism has also been discussed.

Non-catalytic CVD preparation of carbon spheres with a specific size

A simple chemical vapor deposition method was used to prepare carbon spheres (CPS) from toluene without any catalysts. The diameters of CPS are in a range of 60 nm to 1 μm and can be controlled by changing the composition and flow rate of a mixture gas that was used as the carrier gas. The carbon spheres have been systematically studied by scanning electron microscopy (SEM), element analysis, energy dispersive X-rays spectroscopy (EDX), X-ray diffraction (XRD) and ultra-violet laser Raman spectroscopy. The SEM examination shows that these carbon spheres have a ball-like and chain-like morphology, all of which have smooth surfaces and a quite uniform diameter. The element analysis reveals that the carbon content of the spheres is over 97.0% while the EDX analysis shows that more than 92.0% of the carbon spheres is carbon. The XRD and UV-Raman studies reveal that they are not highly graphitized carbons.

Preparation of carbon spheres consisting of amorphous carbon cores and graphene shells

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