Solid Carbon Spheres Research Articles

Curvature-Induced Electron Spin Catalysis with Carbon Spheres.

Here, we report curvature-induced electron spin catalysis by using solid carbon spheres as catalysts, which were synthesized using positive curvature molecular hexabromocyclopentadiene as a precursor molecule, following a radical coupling mechanism. The curvature spin of carbon is regarded as an overlapping state of σ- and π-radical, which is identified by the inverse Laplace transform of pulse-electron paramagnetic resonance. The growth mechanism of carbon spheres abiding by Kroto's model, is supported by the density functional theory study of thermodynamics and kinetics calculations. The solid carbon spheres present excellent catalytic behaviour of oxidation coupling of amines to form corresponding imines with the conversion of >99%, selectivity of 98.7%, and yield of 97.7%, which is attributed to the predominantly curvature-induced electron spin catalysis of carbon, supported by the calculation of oxygen adsorption energy. This work proposes a view of curvature-induced spin catalysis of carbon, which opens up a research direction for curvature-induced electron spin catalysis.

Curvature‐Induced Electron Spin Catalysis with Carbon Spheres

Here, we report curvature‐induced electron spin catalysis by using solid carbon spheres as catalysts, which were synthesized using positive curvature molecular hexabromocyclopentadiene as a precursor molecule, following a radical coupling mechanism. The curvature spin of carbon is regarded as an overlapping state of σ‐ and π‐radical, which is identified by the inverse Laplace transform of pulse‐electron paramagnetic resonance. The growth mechanism of carbon spheres abiding by Kroto’s model, is supported by the density functional theory study of thermodynamics and kinetics calculations. The solid carbon spheres present excellent catalytic behaviour of oxidation coupling of amines to form corresponding imines with the conversion of >99%, selectivity of 98.7%, and yield of 97.7%, which is attributed to the predominantly curvature‐induced electron spin catalysis of carbon, supported by the calculation of oxygen adsorption energy. This work proposes a view of curvature‐induced spin catalysis of carbon, which opens up a research direction for curvature‐induced electron spin catalysis.

Hydrogenation of cinnamaldehyde over palladium nanoparticles supported on functionalized N-doped solid carbon spheres

Hydrogenation of cinnamaldehyde over palladium nanoparticles supported on functionalized N-doped solid carbon spheres

Transmission Electron Microscopic Analysis of Copper Oxide Nanoparticles in the Jet A-1 Deposits Containing Solid and Hollow Carbon Spheres

Transmission Electron Microscopic Analysis of Copper Oxide Nanoparticles in the Jet A-1 Deposits Containing Solid and Hollow Carbon Spheres

Synthesis of hollow carbon spheres by chemical activation of carbon nanoparticles for their use in electrochemical capacitor

Naphthalene combustion has been used to synthesize grams per hour of solid carbon spheres (CS). The carbon soot was activated by acid treatment consisting in a mixture of HNO3 and H2SO4 (1/3 v/v) to produce hollow carbon spheres (HCS). The effect of two concentrations of CSs (5 and 10 mg mL−1) in the acid mixture, on the physicochemical properties of the activated HCSs was studied. The HSCs were subjected to a thermal treatment to increase their graphitization to enhance their electrical conductivity. High-resolution transmission electron microscopy confirmed the formation of HCSs due to the acid treatment whereas FTIR spectra showed that the chemical activation produced functional groups on the carbon spheres surface and the heat treatment effect to remove some of them as well. A specific surface area of 300 m2 g−1 and a large density of micropores for the acid-treated CSs as well as the heat-treated CSs were estimated by analysis of N2 adsorption-desorption isotherms. A specific capacitance 70 F g−1 was calculated by cyclic voltammetry of the acid and thermally treated HCSs at 5 mV s−1, for both CS concentrations, indicating the possibility of synthesizing these HCSs using a simple method in large quantities for their use in electrochemical capacitors.

Activated Hollow and Solid Carbon Spheres for Enhanced Removal Efficiency of Pharmaceutical Pollutants and Heavy Metals in Water

Activated Hollow and Solid Carbon Spheres for Enhanced Removal Efficiency of Pharmaceutical Pollutants and Heavy Metals in Water

Solid Carbon Spheres with Interconnected Open Pore Channels Enabling High-Efficient Polysulfide Conversion for High-Rate Lithium-Sulfur Batteries.

Hollow carbon spheres or core-sheath porous carbon spheres have been widely used in the S cathode of lithium-sulfur batteries. However, the sphere shells or the pore walls may block the free transport of active species to a certain extent and may have a negative influence on the effective accommodation of elemental sulfur. Herein, solid but porous carbon spheres (PNCS) with large porosity and high specific surface area are developed, which enable high sulfur loading and ample cathode/electrolyte contact area, and the interconnected open pore channels significantly shorten the ion/electron transport pathways. Together with high-conducting nitrogen-doped graphene (NG), facilitated polysulfide conversion kinetics is realized in the as-assembled Li-S batteries, which deliver a high initial discharge capacity of 1445 mAh g-1 at 0.2 C, excellent rate capability of 872 mAh g-1 at 4 C, and low capacity decay of 0.047% per cycle for 500 cycles at 1 C. Even under high sulfur loading of 5.5 mg cm-2 and low electrolyte/sulfur (E/S) ratio of 5 μL mg-1, the Li-S batteries still display high specific capacities of 896 mAh g-1 and 4.96 mAh cm-2. The real application of PNCS/NG is also demonstrated by the corresponding Li-S pouch cells showing high discharging capacity and stable open circuit voltage. This work exhibits the promising application of the solid carbon spheres as the S host for effectively addressing the polysulfide shuttle and propelling the development of high-performance Li-S batteries.

The structure–activity correlation of single-site Ni catalysts dispersed onto porous carbon spheres toward electrochemical CO2 reduction

Single-site metal catalysts (SSMCs) with high activity and stability have been widely applied as electrocatalysts for electrochemical CO2 reduction reaction (CO2RR) process. However, it remains challenging for precise controlling the nanoarchitectures and atomic metal sites of SSMCs to investigate their corresponding structural and related catalytic properties toward CO2RR. In this work, four categories of Ni based SSMCs with different nanoarchitectures were successfully synthesized, including Ni-N doped solid carbon spheres with micropore (Ni-N/C-S-Micro), Ni-N doped hollow carbon spheres with micropore (Ni-N/C–H-Micro), Ni-N doped hollow carbon spheres with mesopore (Ni-N/C–H-Meso), and Ni-N doped hollow carbon spheres with micropore and mesopore (Ni-N/C–H-Micro/Meso). Ni-N/C-S-Micro and Ni-N/C–H-Micro were favorable for the generation of atomic Ni sites in SSMCs, resulting in higher loading amount of Ni, while Ni-N/C–H-Meso with open structure leads to the aggregation of Ni species during pyrolysis. In comparison with Ni-N/C-S-Micro, carbon spheres with hollow and mesoporous structures can enhance the diffusion of CO2 and improve the catalytic activity of per Ni site toward CO2RR process. Thus, Ni-N/C–H-Meso shows the highest turnover frequencies (TOF) value for CO2RR to CO. This study provides a SSMCs design protocol for investigation the SSMCs correlation of structure and properties toward electrochemical conversions.

Toward Theoretical Capacity and Superhigh Power Density for Potassium-Selenium Batteries via Facilitating Reversible Potassiation Kinetics.

Potassium-selenium (K-Se) batteries attract tremendous attention because of the two-electron transfer of the selenium cathode. Nonetheless, practical K-Se cells normally display selenium underutilization and unsatisfactory rate capability. Herein, we employ a synergistic spatial confinement and architecture engineering strategy to establish selenium cathodes for probing the effect of K+ diffusion kinetics on K-Se battery performance and improving the charge transfer efficiency at ultrahigh rates. By impregnating selenium into hollow and solid carbon spheres with similar diameters and porous structures, the obtained parallel Se/C composites possess nearly identical selenium loadings, molecular structures, and heterogeneous interfaces but enormously different paths for K+ diffusion. Remarkably, as the solid-state K+ diffusion distance is significantly reduced, the K-Se cell achieves 96% of 2e- transfer capacity (647.1 mA h g-1). Reversible capacities of 283.5 and 224.1 mA h g-1 are obtained at 7.5 and 15C, respectively, corresponding to an unprecedented high power density of 8777.8 W kg-1. Quantitative kinetic analysis demonstrated a twofold higher capacitive charge storage contribution and a 1 order of magnitude higher K+ diffusion coefficient due to the short K+ diffusion path. By combining the determination of potassiation products by ex situ characterization and density functional theory (DFT) calculations, it is identified that the kinetic factor is decisive for K-Se battery performances.

The effect of temperature on structure and permittivity of carbon microspheres as efficient absorbent prepared by facile and large-scale method

Based on the concept of environment-friendly development strategy, green preparation method is crucial. Therefore, starch-derived micron solid carbon spheres (SCs) were fabricated via spray-drying followed by carbonization processing, in which is no any harmful substances in whole process. Through tuning the carbonization temperature, SCs with a moderate degree of graphitization and intrinsic defects can be obtained. The microstructure, permittivity and microwave absorption of SCs were studied. Results show that the SCs with a larger number of micropores is composed of nanocrystalline regions and amorphous areas. The paraffin-based composites with 25 wt% SCs carbonized at 800 °C displays a strong microwave loss feature, the minimum reflection loss of −64.8 dB at 9.02 GHz with thickness of 2.57 mm. Meanwhile, the effective absorption band (<-10 dB) can reach 3.1 GHz with the thickness of 2.22 mm, covering 78% of X-band, which because of its good impedance matching and dielectric loss ability resulted from the synergistic effect between the microstructure and graphitization. This work offers a facile, larger-scale and environmental-friendly method for the preparation of micron carbon-based absorbents that can serves as an alternative to nano-scale absorbents to overcome the poor dispersion of nanoparticle in the matrix.

Hollow nitrogen-doped carbon nanospheres as cathode catalysts to enhance oxygen reduction reaction in microbial fuel cells treating wastewater

Hollow nanospheres play a pivotal role in the electro-catalytic oxygen reduction reaction (ORR), which is a crucial step in microbial fuel cell (MFC) device. Herein, the hollow nitrogen-doped carbon nanospheres (HNCNS) were synthesized with the sacrifice of silica coated carbon nanospheres (CNS@SiO2) as template. HNCNS remarkably enhanced the ORR activity compared to the solid carbon and solid silica spheres. By tuning calcination temperature (800–1100 °C), the surface chemistry properties of HNCNS were effectively regulated. The optimal HNCNS-1000 catalyst which was calcined at 1000 °C exhibited the highest ORR activity in neutral media with the onset potential of 0.255 V and half-wave potential of −0.006 V (vs. Ag/AgCl). Single chamber MFC (SCMFC) assembled with HNCNS-1000 cathode unveiled comparable activity to a conventional Pt/C reference. It showed the highest maximum power density of 1307 ± 26 mW/m2, excellent output stability of 5.8% decline within 680 h, chemical oxygen demand (COD) removal of 94.0 ± 0.3% and coulombic efficiency (CE) of 7.9 ± 0.9%. These excellent results were attributed to a cooperative effect of the optimized surface properties (e.g., structural defects, relative content of pyrrolic nitrogen and specific surface area) and the formation of hollow nanosphere structure. Furthermore, the positive linear relationship of the structural defects and pyrrolic nitrogen species with the maximum power generation in SCMFC were clearly elucidated. This study demonstrated that the cost effective HNCNS-1000 was a promising alternative to commercial Pt/C catalyst for practical application in MFCs treating wastewater. Our result revealed the effectiveness of MFC fabricated with HNCNS-1000 cathode catalyst in terms of power generation and wastewater treatment.

A comparison of fluorescent N-doped carbon dots supported on the surface of hollow and solid carbon spheres, and solid silica spheres

Fluorescent carbon dots (Cdots) have attracted many researchers due to their strong optical photoluminescence (PL) properties; however, due to their small size they agglomerate in the solid state which makes it difficult to remove them from solution. To overcome these problems, Cdots can be deposited on a support, but to date, few systematic studies of Cdots-support systems have been reported, especially those on carbon supports. Herein, we report a systematic study of the effect of the use of N-Cdots (5, 10, 15 and 20%) supported on the surface of hollow carbon spheres (HCSs), solid carbon spheres (SCSs) and silica spheres (SSs). The morphology of the Cdots and their composites (Cdots/SSs, Cdots/HCSs and Cdots/SCSs) was studied by TEM, TGA, XRD, FTIR, UV–vis and PL techniques. The FTIR, XRD and TGA data suggest different interactions of the Cdots with the supports. The PL quantum yield for bare Cdots was 34% and this value was dependent on the supports, in the order Cdots/SSs > Cdots/HCSs > Cdots/SCSs due to different interactions between the Cdots and the support.

Porous yolk–shell-structured carbon nanospheres for electrochemical energy storage

Yolk–shell-structured nanospheres have attracted potential applications in various fields due to their unique structural properties, which combines the advantages of mesoporous carbon and hollow structure. Herein, uniform porous yolk–shell carbon nanospheres (PYCNs) were obtained through a two-step coating employing resorcinol–formaldehyde (RF) resin spheres as a core, which is widely used due to its low-cost, high carbon residue and stability. The pre-formed RF spheres cores were subsequently coated with double shells of compact silica layer and polybenzoxazine/silica (PB/SiO2) hybrid in sequence, in which the intermediate silica layer and the silica from PB/SiO2 hybrid layer were subsequently etched off to create gap of yolk–shell structure and mesopore of shell for PYCNs. The resultant PYCNs possessed uniform spherical morphology with yolk–shell structure, mesoporous shell and a certain of N-doping, which endows it with a better electrochemical performance in supercapacitor than that of solid carbon spheres derived from RF spheres pyrolysis directly.

Design bifunctional nitrogen doped flexible carbon sphere electrode for dye-sensitized solar cell and supercapacitor

Developing a highly effective bifunctional electrode material is vital to the self-powered integrated electronics that combine the energy conversion unit of the dye-sensitized solar cell (DSC) and the energy storage unit of the supercapacitor. In this study, a nitrogen doped carbon sphere (NCS) is synthesized to promote the electrode activity as compared with that of the conventional solid carbon sphere (SCS) in both DSC and supercapacitor systems. In the DSC system, the rigid and flexible devices using NCS counter electrodes yield power conversion efficiencies of 8.64% and 6.73%, much higher than those of the devices using SCS counter electrodes (6.96% and 4.57%). As a supercapacitor working electrode, the NCS shows a remarkable specific capacitance of 224.6 F g−1, much higher than the counterpart value of the SCS electrode (124.9 F g−1) under the same conditions, which demonstrates capacitance improvement by 79.8%. Moreover, NCS preserves more than 90.0% of their initial capacitance after long term stability tests, suggesting a perfect cycle life. The enhanced activity of the NCS can be ascribed to the improved conductivity, charge transfer, and mass transport processes caused by nitrogen doping.

An ionic liquid-present hydrothermal method for preparing hawthorn sherry ball shaped palladium (Pd)-based composite catalysts for ethanol oxidation reaction (EOR)

For the first time, a hawthorn sherry ball shaped Pd-based composite catalyst for EOR was prepared via an ionic liquid-present two-step hydrothermal method in this work. In the first hydrothermal step, micron-scale solid carbon spheres (MSCS) were fabricated in the presence of glucose, an ionic liquid of 1-butyl-3-methyl tetrafluoroboric acid and one kind of surfactant. And in the second hydrothermal process, sesame like Pd particles were immobilized on the surface of MSCS forming a hawthorn sherry ball shaped Pd-based composite catalyst (denoted as Pd/MSCS) using PdO as the source of Pd. In the course of preparing MSCS, four kinds of surfactants were respectively employed desiring to study the influence of surfactant type on the physicochemical properties of the produced samples. The prepared MSCS and Pd/MSCS were examined majorly by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It was addressed by SEM images that in the presence of SDS and EDTA, hawthorn sherry ball shaped Pd-based composite catalysts were successfully prepared. XRD and XPS analysis substantially documented that metallic palladium was the main component of the synthesized Pd/MSCS catalysts. The electrocatalytic abilities of the Pd/MSCS catalysts for EOR were examined in 1 M C2H5OH alkaline solution mainly utilizing cyclic voltammetry (CV) and chronoamperometry (CA), illustrating that all produced Pd/MSCS catalysts had an electrocatalytic activity towards EOR, and the forward peak current density of EOR on the catalyst of Pd/MSCS (prepared in the presence of SDS) was 7 times larger, along with 60 mV decrease in the onset potential of EOR, than that on the Pd/MSCS (prepared with CATB) catalyst. Summarily, a very cost-effective and facile method for fabricating hawthorn sherry ball shaped Pd-based composite catalysts towards EOR was created in this work, which was very meaningful not only to the further development of EOR catalysts but also to the exploration of micron-devices.

CVD Synthesis of Solid, Hollow, and Nitrogen-Doped Hollow Carbon Spheres from Polypropylene Waste Materials

Plastic waste leaves a serious environmental footprint on the planet and it is imperative to reduce this. Consequently, recycling has been regarded as an important approach in providing one solution to this problem. In this study, we enhanced the value of polypropylene (PP) plastic waste by using it as a hydrocarbon source to synthesize a variety of spherical carbon nanomaterials. Here, a CVD method was used to decompose the PP initially into a hydrocarbon gas (propylene). Thereafter, PP was employed to synthesize solid carbon spheres (SCSs), hollow carbon spheres (HCSs), and nitrogen-doped hollow carbon spheres (NHCSs). The latter two were made using a silica template while the N-doping was achieved by the addition of melamine to PP. Yields obtained were between 12–20%. The SCSs (d = 800 nm to 1200 nm), HCSs (id = 985 nm; shell width = 35 nm), and NHCSs (id = ca. 1000 nm; shell width = 40 nm) were all characterized by TEM, SEM, TGA, laser Raman spectroscopy, and XPS.

Synthesis and Characterization of Carbon Spheres/Poly(Methyl Methacrylate) Composites with Enhanced Electrical Conductivity and Vickers Microhardness

Carbon spheres used as filler materials are ideal and promising nanostructures to obtain composites with enhanced electrical and mechanical properties. Solid carbon spheres synthesized previously in this research by chemical vapor deposition were incorporated in poly(methyl methacrylate) through solution mixing at different loads (5 wt.%, 7 wt.% and 9 wt.%). Scanning electron microscopy showed a uniform carbon sphere dispersion into the polymer matrices. The characteristic peaks of carbon spheres, D-band at 1321 cm−1 and G-band at 1593 cm−1, were observed in Raman spectroscopy. Fourier transform infrared spectroscopy determined the main functional groups of composites corresponding to C–H, C–O, C=O, CH2 and CH3 stretching. The composites were evaluated by the Vickers Microhardness (HV), the Van der Pauw and the two-point methods. The hardness and electrical conductivity were enhanced according to the carbon sphere loading increase. The maximum carbon sphere load (9 wt.%) in composites showed an important microhardness improvement (147%). Electrical conductivity values significantly increased until 1.66 × 10−3 S/cm (10 orders of magnitude of improvement) at 9 wt.% of carbon sphere composites.

Formation of hollow and solid carbon spheres in thermally stressed jet fuel in the low temperature autoxidation regime

We report the formation of hollow and solid carbon spheres and spherical nanostructures by self-assembly through thermal stressing of jet fuel (Jet A-1) in the autoxidation temperature range. The characterization of Jet A-1 deposits was conducted by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS). Additionally, high resolution mass spectrometry with electro spray ionization source (ESI-MS) have been used to identify large molecular weight compounds in the mass range 350 Da to 1000 Da in the thermally stressed fuel. Fourier transform infrared (FTIR) spectroscopy analysis revealed oxygenated functional groups in the jet fuel treated by flask tests. Compositional analysis of deposit by TEM EDS and scanning transmission electron microscopy (STEM) and a high-angle annular dark field (HAADF) detector identified multiple trace metallic elements such as Cu, Fe, Zn, Sn, Mg, Al and heteroatoms S, N, O. Hollow carbon sphere formation was due to the catalytic activity of trace metals. Spherical particle growth in this method also appeared to follow Ostwald ripening mechanism. Simple flask static tests in the low temperature regime with jet fuel as hydrocarbon source without externally added catalysts thus is a novel method for hollow and solid carbon sphere synthesis and presented in this paper.

Borax-assisted hydrothermal carbonization to fabricate monodisperse carbon spheres with high thermostability

A modified hydrothermal carbonization (HTC) process in the presence of borax was developed to produce uniform and monodispersed micro-carbon spheres. Corn starch was used as carbon precursor and borax acts as a structure directing agent. The introduction of borax could catalytically transform the starch into hydroxymethylfurfural (HMF) and favoring the rapid nucleation and slow growth of particle owing to the buffer function of borax additive. The inclusion of borax thus allowed for the controlling of particles morphology as well as tailoring the particle diameters. Uniform solid carbon spheres with a narrow particle size distribution, ranging from 0.6 to 2 μm, was demonstrated by turning the borax concentration and the reaction time in a single-step hydrothermal process. The retained boron content and chemical structure of the carbonaceous products could be adjusted as revealed by inductively coupled plasma (ICP) and Fourier transformed infrared (FTIR) analysis. Furthermore, the boron-dopant increased the final product’s thermostability from 536 °C to 629 °C at 0.70 wt% boron content. This method therefore also provides a facile and novel approach to prepare boron-doped carbon materials.

Comparative investigation of small laccase immobilized on carbon nanomaterials for direct bioelectrocatalysis of oxygen reduction

In this study, different carbon nanomaterials (carbon nanotubes, solid carbon spheres and graphene nanosheets) for immobilizing bacterial small laccase (SLAC) to enable direct bioelectrocatalysis of oxygen reduction were comparatively investigated. Highest bioelectrocatalytic current response was achieved with ethanol-assisted SLAC adsorption on single-walled carbon nanotubes. Direct electron transfer (DET) rates were determined and generally shown to be larger with carbon nanomaterials in smaller dimensions or higher surface curvature, i.e., 1.92, 1.05, 1.52, 0.62 and 0.63 s−1 for adsorbed SLAC on single-walled carbon nanotubes (d = ca. 1.5 nm), double-walled carbon nanotubes (d = 2–4 nm), thinner multi-walled carbon nanotubes (d = 8–15 nm), thicker multi-walled carbon nanotubes (d = 20–30 nm) and graphene nanosheets, respectively. No obvious catalytic current response was obtained with solid carbon spheres (d > 200 nm). Surface nanostructures on electrodes with decreased cylindrical diameter could enable a favorable protein orientation of immobilized SLAC for efficient electronic communication between the catalytic copper sites and carbon nanomaterials as revealed by surface vibrational spectroscopy. Moreover, such a difference in DET kinetics of SLAC could be an outcome of synergic effects of surface properties (curvature, oxygen-containing groups, etc.) and conductivity of carbon nanomaterials. It is expected to offer useful information to fabricating carbon-based oxygen-reducing biocathodes of wide working pH range and high tolerance to chloride.