Solid Carbon Spheres Research Articles

Thermal oxidation etching strategy towards mesoporous hollow carbon spheres

The mesoporous hollow carbon spheres have been prepared by thermal oxidation etching strategy, and characterized by transmission electron microscopy and the Brunauer-Emmett-Teller method. The mesoporous hollow carbon spheres can be obtained by means of controlling the thermal oxidation times of solid carbon spheres in air. The mesoporous hollow carbon spheres at the optimum thermal oxidation time of 1.5 h in air showed the highest specific surface and the highest total pore volume. Furthermore, the hollow carbon sphere-sulfur composite cathodes achieved high initial discharge capacity of 1423.9 mAh g−1, excellent discharge capacity and excellent rate performance.

Hollow carbon spheres with artificial surface openings as highly effective supercapacitor electrodes

A novel kind of hollow carbon spheres with artificial surface openings is fabricated as highly effective supercapacitor electrode. This kind of carbon sphere possesses typical hierarchical mesoporous structure with surface area of 670.0 m2 g−1, much higher than that of the conventional hollow carbon spheres and solid carbon spheres. The electrochemical performance of the prepared hollow carbon spheres with surface openings, hollow carbon spheres and solid carbon spheres electrode are evaluated in acidic aqueous electrolyte. The hollow carbon sphere with surface openings electrode shows the optimal capacitive performance due to the specific surface openings and hierarchical mesoporous structure which can provide a large ion-accessible surface area and a loose channel for the electrolyte ions to diffuse into the internal of the spheres, making the internal charge storage sites work more effectively. The hollow carbon spheres with surface openings electrode achieves a remarkable specific capacitance of 272.2 F g−1, much higher than that of the hollow carbon spheres and solid carbon spheres. Besides, the hollow carbon spheres with surface openings preserves 96.9% of its initial capacitance after 10000 charge-discharge cycles, suggesting a perfect cycle life.

Controllable synthesis of N-doped hollow, yolk-shell and solid carbon spheres via template-free method

N-doped carbon spheres with different inner structure have attracted increasing attention due to their low density and high electrical conductivity in supercapacitors. Here, we reported controllable synthesis of hollow, yolk-shell and solid structure carbon spheres via template-free assembly method. Ethanediamine was used as nitrogen source to realize in-situ nitrogen doping and as basic catalyst to drive resorcinol-formaldehyde (RF) resin polymerization. The polymerization degree of internal RF resin tremendously depended on polymerization time, resulting in different levels of heterogeneity of the whole RF resin sphere. This fact made the structural adjustment of carbon spheres from hollow, to yolk-shell and even to solid structure after dissolution of low-molecular-weight RF resin by organic solvents and annealing treatment. As electrode material for supercapacitor, carbon spheres with yolk-shell structure exhibited excellent performance with capacitance of 242 F g−1 at the current density of 1 A g−1 and outstanding cycling life stability (97.3% after 5000 cycles), which may be attributed to its unique structure, high specific surface area (1263 m2 g−1) and pore volume (0.68 cm3 g−1). The strategy of making full use of the difference of polymerization degree of resin provides a new idea for the structural engineering of functional carbon materials.

From Hollow to Solid Carbon Spheres: Time-Dependent Facile Synthesis.

Here, we report a facile route for obtaining carbon spheres with fully tunable shell thickness. Using a hard template in chemical vapor deposition (CVD), hollow carbon spheres, solid carbon spheres, and intermediate structures can be obtained with optimized process time. The resulting carbon spheres with particle diameters of ~400 nm, as well as a controllable shell thickness from 0 to 70 nm, had high Brunauer–Emmett–Teller (BET) specific surface area (up to 344.8 m2·g−1) and pore volume (up to 0.248 cm3·g−1). The sphere formation mechanism is also proposed. This simple and reproducible technique can deliver carbon materials for various applications, e.g., energy storage and conversion, adsorption, catalytic, biomedical, and environmental applications.

Nitrogen-Doped Hollow Mesoporous Carbon Spheres for Efficient Water Desalination by Capacitive Deionization

Water desalination performance of capacitive deionization (CDI) largely depends on electrode materials properties. Rational design and regulation of the structure and composition of electrode materials to acquire high CDI performance is of great significance. Herein, nitrogen-doped hollow mesoporous carbon spheres (N-HMCSs) were investigated as electrode material for CDI application. To understand the effect of structure and composition on CDI performance, another two CDI electrode materials, i.e., hollow mesoporous carbon spheres (HMCSs) and solid mesoporous carbon spheres (SMCSs) were prepared for comparison. The obtained N-HMCSs possessed unique hollow cavity and excellent nitrogen doping property, resulting in fast ion diffusion, good charge transfers ability and fine wettability. Compared with HMCSs and SMCSs electrodes, N-HMCSs electrode exhibited an improved electrosorption capacity and rate, demonstrating the dependence of CDI performance on the synergistic effect of hollow structure and nitrogen ...

Nitrogen doped porous hollow carbon spheres for enhanced benzene removal

Abstract In this work, nitrogen doped hollow carbon spheres (NHCS) were synthesized via modified “silica-assistant” route and further examined as adsorbents for the removal of benzene, which is a typical volatile organic compounds (VOCs). To understand the structure and composition on benzene removal, solid carbon spheres (SCS), nitrogen doped solid carbon spheres (NSCS) and hollow carbon spheres (HCS), were also prepared for comparison. The structure and morphology characterization revealed that the resultant carbon spheres possess uniform spherical shape, abundant micropores and mesopores with solid or hollow structure and high pore volume. Combined with Raman and XPS spectra, the composition of carbon spheres was successfully tailored via introduction of nitrogen atom into carbon matrix. To present the removal performance of carbon spheres for VOCs, the dynamic adsorption behavior was evaluated. Attributed to the combined effect of hollow structure and nitrogen doping, NHCS presents remarkable dynamic adsorption performance for benzene vapor with adsorption capacity of 766 mg/g. The enhancement on desorption behaviors resulting from hollow structure of HCS is confirmed when compared with SCS. Carbon spheres exhibit good regenerability based on desorption experiment. The mechanism of enhanced adsorption performance caused by nitrogen doping is clarified as the combined action of adjustment on porous structure and composition. These results indicate that NHCS would become a promising candidate for VOCs removal.

Synthesis and characterization of solid polymer and carbon spheres derived from an emulsion polymerization reaction of different phenolic compounds with formaldehyde

In this study, polymer spheres (PSs) were prepared by an emulsion polymerization of resorcinol, pyrocatechol, or 3-hydroxypyridine with formaldehyde under basic conditions. Carbon spheres (CSs) were obtained by carbonization of PSs at 900°C, and some of them were activated with KOH and oxygen adsorption-desorption cycles. Resorcinol and pyrocatechol differ in their reactivity during the polycondensation reaction with formaldehyde. The use of 3-hydroxypyridine allowed the introduction of N functionalities in the final CSs obtained. The objective was to examine the effects on the diameter of the carbon spheres, their surface physics and chemistry, and their performance as electrochemical double-layer (EDL) capacitors produced by: i) the replacement of resorcinol with pyrocatechol in the polymerization reaction and the utilization of different carbon sphere activation methods; and ii) the introduction of N functionalities. The size, surface area, micropore volume, total pore volume, and micropore width of the CSs ranged between 159 and 856nm, 7 and 1156m2g−1, 0.06 and 0.46cm3g−1, 0.15 and 0.58cm3g−1, and 0.50 and 1.23nm, respectively. The physically-activated sample showed the highest capacitance at 1Ag−1, 200Fg−1 or 17.3μFcm−2. Capacitance was higher in N-doped samples than in the non-doped sample.

Effect of Cu location and dispersion on carbon sphere supported Cu catalysts for oxidative carbonylation of methanol to dimethyl carbonate

A series of novel composite catalysts consisting of carbon spheres with encapsulated copper species were synthesized by incipient wetness impregnation. To improve catalytic activity, Cu location on the hollow carbon spheres was tuned by ultrasonic-assisted impregnation. The location, dispersion and chemical structure of copper species were characterized by X-ray diffraction, Temperature-programmed reduction, Transmission electron microscopy, N2-physisorption, Atomic absorption spectroscopy, X-ray photoelectron spectroscopy and dissociative N2O adsorption measurements. The results showed that hollow mesoporous carbon spheres have uniform mesopores, which were more favorable to the confinement and dispersion of the active species than solid carbon spheres. The catalyst with Cu species highly dispersed in the mesopores of hollow carbon spheres exhibited superior catalytic performance compared with those with Cu species located outside the support or inside the hollow interiors. The catalyst with ultrafine Cu particles of 2 nm in the mesopores of the 200 nm carbon sphere exhibited a dimethyl carbonate Space-Time Yield of 218.4 mg·g−1cat·h−1, much higher than traditional activated carbon and ordered mesoporous carbon supported Cu catalysts. Interestingly, copper species in the cavity showed high autoreduction ability in spite of poor dispersion after activation, and this catalyst is anticipated to achieve better activity by improving Cu dispersion.

Generation of radical species in CVD grown pristine and N-doped solid carbon spheres using H2 and Ar as carrier gases

A mechanism showing the role of carrier gas on the N-configuration of the post-N-doped CSs synthesized in the presence of (a) H2 and (b) Ar, respectively.

Enzyme- and metal-free electrochemical sensor for highly sensitive superoxide anion detection based on nitrogen doped hollow mesoporous carbon spheres

In this work, a highly sensitive enzyme- and metal-free electrochemical method for superoxide anion (O2−) detection has been developed by employing screen-printed carbon electrodes (SPCE) modified by nitrogen doped hollow mesoporous carbon spheres (N-HMCS). For comparison, solid carbon spheres (SCS) and hollow mesoporous carbon spheres (HMCS) were also synthesized to fabricate the modified SPCE. Compared with SCS/SPCE and HMCS/SPCE, N-HMCS/SPCE displayed a higher electrochemical performance. When applied for electrochemical detection of O2−, N-HMCS/SPCE exhibited a high sensitivity of 1.49μAcm−2μM−1, better than SCS/SPCE and HMCS/SPCE and many of enzyme- or metal-based superoxide anion sensors. N-HMCS is expected to become a new generation of sensing materials for electrochemical analysis of O2−.

Adsorption of rare earth ions using carbonized polydopamine nano carbon shells

AbstractHerein we reported the structure effects of carbon nano-shells prepared by the carbonization of polydopamine for the adsorption of rare earth elements (REEs) for the first time. Solid carbon spheres, 60 nm carbon shells and 500 nm carbon shells were prepared and evaluated for adsorption and desorption of REEs. The adsorption performance of carbon nano-shells for REEs was far superior to the solid carbon spheres. In addition, the effect of acidity on the adsorption and desorption properties was discussed. The good adsorption performance of the carbon nano-shells could be attributed to their pore structure, specific surface area, and the presence of both amine and carbonyl groups from the grafted dopamine.

Synthesis of unique metal oxide/carbon composites via sealed-tube pyrolysis of metal acetylacetonates and the mechanism of their formation

Unique MnO/C and Fe3O4/C composites containing solid carbon spheres are obtained from the inert-ambient sealed-tube pyrolysis of respective metal acetylacetonates.

Carboxylated solid carbon spheres as a novel solid-phase microextraction coating for sensitive determination of phenols in environmental water samples

The high performance separation and enrichment of polar phenols from aqueous matrices is often difficult due to the strong interactions between phenols and water. In this paper, carboxylated solid carbon spheres (SCSs-COOH) were, for the first time, used as a novel coating material in the solid-phase microextraction (SPME) of polar phenols at ultra-trace levels in environmental water samples. Gas chromatography coupled with tandem mass spectrometry (GC–MS/MS) was applied for sample quantification and detection. The novel SCSs-COOH-coated fiber exhibited good thermal stability (>330°C) and higher extraction efficiency than commercial fibers in the extraction of phenols. The Plackett–Burman design was employed to optimize the extraction factors affecting the extraction efficiency through a response surface methodology. A possible phenol extraction mechanism enabled by the SCSs-COOH-coated fiber is proposed. Under the optimized conditions, low detection limits (0.26–2.63ngL−1), a wide linear range (1–1000ngL−1), good repeatability (2.00–9.02%, n=5) and excellent reproducibility (2.08–8.55%, n=3) were achieved. The developed method was validated against several environmental water samples, with satisfactory results being obtained each case.

A low temperature reduction of CCl4 to solid and hollow carbon nanospheres using metallic sodium

Carbon nanospheres are obtained by reacting metallic sodium at 100 °C with tetrachloromethane under a flow of N2 gas at ambient pressure. The product consisted of both hollowed and solid carbon spheres, ranging between 20 and 300 nm in size and comprised of concentrically oriented, disordered graphitic fragments. The maximum surface area recorded for this nanostructured carbon is 830 m2 g−1. Morphological, structural, and chemical analysis of the product is carried out with HR-TEM, BET surface area, XPS, XRD, and Raman spectroscopy. The formation of the spherical shape of the carbon nanoparticles is discussed based on direct observations of the reaction at the interfacial phase boundary.

Eco-friendly, catalyst-free synthesis of highly pure carbon spheres using vegetable oils as a renewable source and their application as a template for ZnO and MgO hollow spheres

Herein we report the eco-friendly and catalyst-free single step synthesis of solid carbon spheres, 1–10 μm in diameter, using vegetable oils derived from different bio-resources as the carbon source.

Design a novel kind of open-ended carbon sphere for a highly effective counter electrode catalyst in dye-sensitized solar cells

A new kind of carbon sphere (denoted as OCS) with an open end on the surface has been synthesized successfully. The designed OCS shows higher electrocatalytic activity than the conventional solid and hollow carbon sphere (denoted as SCS and HCS) as counter electrode (CE) catalyst for the regeneration of both iodide (I−/I3−) and sulfide (T−/T2) redox shuttles in dye-sensitized solar cells (DSCs). For the iodide electrolyte, the DSCs using SCS, OCS, and HCS CEs yield high power conversion efficiency (PCE) values of 7.8, 8.7, and 8.1%, respectively, indicating the potential to replace expensive Pt CE. Most importantly, the carbon sphere catalysts exhibit obvious advantages when applied in sulfide redox shuttle. The OCS-CE based DSCs produces a high PCE of 6.4%, much higher than that for Pt-CE based DSCs (4.1%). The high catalytic activity of OCS benefits from the sufficient contact between the redox shuttle with the external and internal surfaces of OCS because an open end exists on the surface of OCS, which provide a diffusion channel for the electrolyte into the inner of OCS. This strategy for designing open-ended structure is highly important for the fields of drug delivery, nanodevice, and adsorption, but not confined to catalysis.

A Closed-Loop Process from Microwave-Assisted Hydrothermal Degradation of Starch to Utilization of the Obtained Degradation Products as Starch Plasticizers

A green closed-loop water-based process for chemical recycling of starch was demonstrated. The process starts from microwave-assisted controllable starch degradation to functional chemicals and continues to utilization of the formed degradation products, glucose and levulinic acid (LA), as starch plasticizers. The degradation process and the effect of process parameters on the formed degradation products and residues were carefully fingerprinted by multiple techniques, e.g., NMR, ESI-MS, FTIR imaging, UV–vis, and SEM. The degradation process took place in three steps, proceeding from rupture of starch granules and oligosaccharide formation to further hydrolysis to glucose. Finally, at well-defined time point rapid degradation of glucose to LA and formic acid (FA) was initiated through a 5-hydroxymethyl furfural (5-HMF) intermediate. 5-HMF also participated in carbonization reactions leading to formation of solid carbon spheres. Through selection of processing parameters, LA could be produced in high yield with 95% selectivity. The results demonstrated that microwave-assisted degradation of starch leads to well-defined controllable degradation products. These products are directly reusable as plasticizers for new starch products, which suggest great opportunities for biomass and starch recycling, opening the door toward potential industrial applications.

Synthesis of branched, nano channeled, ultrafine and nano carbon tubes from PET wastes using the arc discharge method

Upcycling polymer wastes into useful, and valuable carbon based materials, is a challenging process. We report a novel catalyst-free and solvent-free technique for the formation of nano channeled ultrafine carbon tubes (NCUFCTs) and multiwalled carbon nanotubes (MWCNTs) from polyethylene terephthalate (PET) wastes, using rotating cathode arc discharge technique. The soot obtain from the anode contains ultrafine and nano-sized solid carbon spheres (SCS) with a mean diameter of 221nm and 100nm, respectively, formed at the lower temperature region of the anode where the temperature is approximately 1700°C. The carbon spheres are converted into long “Y” type branched and non-branched NCUFCTs and MWCNTs at higher temperature regions where the temperature is approximately 2600°C, with mean diameters of 364nm and 95nm, respectively. Soot deposited on the cathode is composed of MWCNTs with a mean diameter of 20nm and other nanoparticles. The tubular structures present in the anode are longer, bent and often coiled with lesser graphitization compared to the nanotubes in the soot on the cathode.

Evidence of Ostwald ripening during evolution of micro-scale solid carbon spheres.

Ostwald ripening is an evolutionary mechanism that results in micro-scale carbon spheres from nano-scale spheres. Vapor-phase carbon elements from small carbon nanoparticles are transported to the surface of submicron-scale carbon spheres, eventually leading to their evolution to micro-scale spheres via well-known growth mechanisms, including the layer-by-layer, island, and mixed growth modes. The results obtained from this work will pave the way to the disclosure of the evolutionary mechanism of micro-scale carbon spheres and open a new avenue for practical applications.

Mesopore-functional carbon sphere nanochains and their integration with alloy nanoparticles for enhanced electrochemical performances

One of novel porous 1-D architectures, mesopore-functional carbon sphere nanochains (MCSNs), with highly interrelated networks have been directly evolved from the colloidal carbon sphere nanochains (CCSNs) through a unique Li2CO3-molten salt strategy. The PtRu/MCSNs hybrid system, achieved by rational integration of 2.5-nm-size PtRu alloy NPs into the mesopores of MCSNs were prepared, and for comparison, the solid carbon sphere nanochain (SCSN)-supported PtRu NPs (PtRu/SCSN) and benchmark carbon (Vulcan XC-72)-supported PtRu (PtRu/C) were also prepared. It is demonstrated that the PtRu/MCSN hybrid system exhibited superior catalytic properties toward methanol oxidation with specially enhanced catalytic activity and desirable stability. The forward peak current density of PtRu/MCSNs (437mAmg−1) was obviously much higher than those of PtRu/SCSNs (265mAmg−1) and PtRu/C (310mAmg−1). The onset potential of PtRu/MCSNs (0.24V) is much earlier than those of PtRu/SCSNs (0.38V) and PtRu/C (0.37V). This attractive efficiency can be ascribed to the functionalities of mesoporous carbon support, which affords more efficient electron transfer and better mass transport, maximizing the availability of nano PtRu catalysts.