Nanoporous Carbon Spheres Research Articles

A Gram Scale Soft-Template Synthesis of Heteroatom Doped Nanoporous Hollow Carbon Spheres for Oxygen Reduction Reaction.

Heteroatom-doped nanoporous carbon materials with unique hierarchical structures have been shown to be promising supports and catalysts for energy conversion; however, hard-template methods are limited by their inflexibility and time-consuming process. Soft-template methods have been suggested as an alternative, but they are limited by their picky requirements for stable reactions and the few known precursors for small-batch synthesis. In this study, a gram-scale soft-template-based silica-assisted method was investigated for producing nitrogen-doped hollow nanoporous carbon spheres (N-HNCS). Nitrogen doping is accomplished during preparation with enhanced electrocatalytic activity without complicating the methodology. To investigate the effect of the unique structural characteristics of N-HNCS (specific surface area: 1250 m2 g-1; pore volume: 1.2 cm3 g-1), cobalt was introduced as an active center for the oxygen reduction reaction. Finely tuned reaction conditions resulted in well-dispersed cobalt particles with minimal agglomeration. This sheds light on the advancement of new experimental procedures for developing more active and promising non-noble catalysts in large and stable batches.

Nanoporous Hollow Carbon Spheres Derived from Fullerene Assembly as Electrode Materials for High-Performance Supercapacitors

The energy storage performances of supercapacitors are expected to be enhanced by the use of nanostructured hierarchically micro/mesoporous hollow carbon materials based on their ultra-high specific surface areas and rapid diffusion of electrolyte ions through the interconnected channels of their mesoporous structures. In this work, we report the electrochemical supercapacitance properties of hollow carbon spheres prepared by high-temperature carbonization of self-assembled fullerene-ethylenediamine hollow spheres (FE-HS). FE-HS, having an average external diameter of 290 nm, an internal diameter of 65 nm, and a wall thickness of 225 nm, were prepared by using the dynamic liquid-liquid interfacial precipitation (DLLIP) method at ambient conditions of temperature and pressure. High temperature carbonization (at 700, 900, and 1100 °C) of the FE-HS yielded nanoporous (micro/mesoporous) hollow carbon spheres with large surface areas (612 to 1616 m2 g-1) and large pore volumes (0.925 to 1.346 cm3 g-1) dependent on the temperature applied. The sample obtained by carbonization of FE-HS at 900 °C (FE-HS_900) displayed optimum surface area and exhibited remarkable electrochemical electrical double-layer capacitance properties in aq. 1 M sulfuric acid due to its well-developed porosity, interconnected pore structure, and large surface area. For a three-electrode cell setup, a specific capacitance of 293 F g-1 at a 1 A g-1 current density, which is approximately 4 times greater than the specific capacitance of the starting material, FE-HS. The symmetric supercapacitor cell was assembled using FE-HS_900 and attained 164 F g-1 at 1 A g-1 with sustained 50% capacitance at 10 A g-1 accompanied by 96% cycle life and 98% coulombic efficiency after 10,000 consecutive charge/discharge cycles. The results demonstrate the excellent potential of these fullerene assemblies in the fabrication of nanoporous carbon materials with the extensive surface areas required for high-performance energy storage supercapacitor applications.

Nanoporous nitrogen-doped graphitic carbon hollow spheres with enhanced electrochemical properties

The direct pyrolysis of nanostructured poly(N-methylaniline) (PNMA) produced nanoporous hollow carbon spheres with a high atomic percentage of nitrogen doping, and these displayed enhanced oxygen reduction activity and supercapacitive properties.

Synthesis and Characteristics of Nanoporous Carbon Spheres /S Composite as Cathode Material for Li-S Battery

Synthesis and Characteristics of Nanoporous Carbon Spheres /S Composite as Cathode Material for Li-S Battery

Self-assemblying behaviour of activated microporous carbon microspheres functionalized via water filtration process

Activated carbon spheres are truly innovative materials with their porous micro/nanostructure that gives them tunable and controllable surface properties (i.e. high surface area, size and orientation of pores etc.). They have great potential for applications as adsorbents for cleaning/purification of water, air and chemical substances, catalyst supports, energy storage and conversion, adsorption of chemical warfare agents, filtration and others. Magnetic functionalization of highly porous and high surface areas of activated carbons have received considerable attention for their more sophisticated and advanced utilization as “smart” and “self-assemblying” purposes. In this study, a novel fabrication technique was used to synthesize activated high compressive strength nanoporous carbon spheres. The functionalization via adsorption/impregnation of magnetic substances was occured during a well-known water treatment-filtering route to fill the pores with nano-sized magnetic particles. Unusually active and dynamic interactions of the magnetic phases were observed upon contacting into each other revealing self-assemblying behaviour of activated carbon microspheres. Dynamic magnetical interaction of self assemblying behaviour of these spheres may have further and advanced applications for variety of purposes.

Starch-based activated carbon micro-spheres for adsorption of methane with superior performance in ANG technology

In current research work, Nano porous carbon spheres were synthesized for efficient methane (CH4) adsorption. To this end, starch was employed as the starting carbon source which was carbonized at 800 °C. Therefore, in order to activate the carbonized samples, different ratios of KOH were used. The activation process was performed using Carbon: KOH ratios of 1:1, 1:2, and 1:4 at 800 °C. The prepared adsorbents were characterized by different techniques including FESEM, X-ray diffraction, FTIR, and BET. Furthermore, CH4 adsorption experiments were carried out on the prepared adsorbents which yielded very good performance. It was found that increasing the KOH content in the activation process increases both the specific surface area and total pore volume, which in turn enhanced the CH4 uptake. As a result of activation method, the best nano porous sample with Carbon:KOH ratio of 1:4 showed high specific surface area and pore volume up to 2222.3 m2/g and 1.72 cm3/g, respectively. The adsorbents had superior adsorption capacity of 12.81 mmole/g at 35 bar, which is much higher than those of literature. This adsorbent with excellent CH4 adsorption performance can be exploited in Adsorbed Natural Gas (ANG) technology to ensure energy storage and usage of high efficiencies.

Bi-continuous nanoporous carbon sphere derived from SiOC as high-performance anodes for PIBs

Potassium-ion batteries (PIBs) are considered as promising alternative candidates to replace lithium-ion batteries due to their low cost, adequate reserves and high energy density. However, a large ionic radius of K+ ions leads to a huge volume expansion and a low ion diffusion rate, restricting its cycling stability and rate performance. Herein, bi-continuous and nanoporous carbon spheres (BC-NCS), consisting of continuous nanocarbon framework and interconnected nanopores, are designed and prepared by etching carbon-rich SiOC ceramics. The interconnected nanopores provide fast ion diffusion channels and sufficient room for tolerating the volume expansion, thus leading to high rate performance and long cycle stability, while the continuous carbon framework possesses a defective nature, an expanded interlayer distance (0.39 nm) and various oxygen‐containing functional groups on its surface induced during the etching process, further endowing it with high reversible capacity and stability. Therefore, the BC-NCS exhibits a high initial reversible capacity (336 mAh g−1 at 0.1 A g−1), long cycle and high rate performance (191 mAh g−1 after 2000 cycles at 0.5 A g−1). Importantly, we investigate the potential application of bi-continuous carbon materials in high performance PIBs, and the bi-continuous structure could be induced into various active materials for the application in different batteries.

Preparation and optimization of nanoporous hollow carbon spheres /S composite cathode materials for Li-S battery

Preparation and optimization of nanoporous hollow carbon spheres /S composite cathode materials for Li-S battery

Large scale synthesis of nitrogen-doped nanoporous carbon spheres based on miniemulsion polymerization for efficient dye removal

Functional nanoporous carbon spheres (NPCS) are important for applications ranging from adsorption, catalysis, separation to energy storage and biomedicine. We demonstrated a facile method to synthesize uniform NPCS, involving the formation of polyacrylonitrile@poly (γ-methacryloxypropyl trimethoxysilane) (PAN@PMPS) composite particles via seeded miniemulsion polymerization of PAN nanoparticles (NPs), carbonization, and subsequent removal of the outer PMPS shell. The influences of the addition of water phase inhibitor sodium nitrite and crosslinking agent divinylbenzene on the morphologies of PAN@PMPS composite particles were investigated. The adsorption performance of NPCS towards methylene blue (MB) was investigated. The results showed that uniform PAN@PMPS composite particles were obtained with average diameters of ~ 149 nm when using NaNO2 as water phase inhibitor. PMPS layer prevented PAN core aggregation/fusion during the carbonization process, resulting in the formation of individual NPCS. Uniform NPCS exhibiting diameters of ~ 122 nm, with the accessible surface area (~ 202 m2/g), and high nitrogen content (13.75 wt%) was obtained. NPCS exhibited excellent adsorption capacity towards MB with the maximum value of 117.89 mg/g at 298 K from aqueous solution. This miniemulsion polymerization-based strategy provides a new, facile approach to prepare high-performance porous carbon spheres in industrialization promise.

Nanoporous carbon spheres derived from metal-phenolic coordination polymers for supercapacitor and biosensor

The conversion of plant polyphenol to multi-functional nanoporous carbon spheres (NCSs) is desirable and challenging. Tannic acid (TA), as one kind of plant polyphenol, has been regarded as one of potential renewable carbon sources for nanoporous carbon materials. However, the nanoporous carbon materials derived from TA usually show low surface area and irregular morphology, which partially limit their broad applications. Herein, we demonstrate the successful synthesis of NCSs with high surface area (up to 2221 m2/g) and uniform diameter (∼120 nm) by direct carbonization of zinc-phenolic coordination polymer using TA as a carbon source. The zinc contents play an important role in tailoring the porosity of NCSs. The specific surface area of NCSs can be adjusted in the range of 527–2221 m2/g as the zinc contents in the coordination polymers changed from 0 to 8.6 wt%. To verify the multi-functions of NCSs, such carbon spheres are further used as a sensing platform for the analysis of nucleic acid variants with high selectivity and low limit of detection, and electrode material for supercapacitor with high specific capacitance, good capacitance retention, and excellent cyclic stability.

A high-rate and ultrastable anode enabled by boron-doped nanoporous carbon spheres for high-power and long life lithium ion capacitors

Lithium ion capacitors (LICs) hold potentials to bridge the gap between lithium ion batteries and supercapacitors; however, the imbalance of electrochemical kinetic and stability between Li+ storage anode and capacitive cathode has been the key bottleneck. Herein, we report a high-rate and ultrastable anode for this issue, consisting of boron-doped nanoporous carbon spheres which are synthesized by a continuous spraying-assisted co-assembly process. Experimental and computational investigations as well as the comparison with a nitrogen-rich carbon indicate that boron species enhances ion-surface interactions, electron/ion conductivity and carbon framework cycling firmness, leading to dramatically improved rate and cycling performances, which outperform the extensively explored nitrogen doped carbons and most reported high-rate anode materials. By pairing a coal-derived microporous graphene cathode, we constructed a full-carbon LIC device exhibiting high energy and power densities (207 Wh kg−1 at 511 W kg−1 and still 136 Wh kg−1 at 17.06 kW kg−1), as well as an unprecedented cycling stability with no capacity decay after 15,000 cycles at 2 A g−1. This work not only offers a fundamental basis to understand the enhanced anode performance by doping boron into carbon framework but also provides an effective strategy to circumvent the kinetic and stability discrepancies between anode and cathode for high-performance LICs.

Individual Nanoporous Carbon Spheres with High Nitrogen Content from Polyacrylonitrile Nanoparticles with Sacrificial Protective Layers

Functional nanoporous carbon spheres (NPC-S) are important for applications ranging from adsorption, catalysis, separation to energy storage, and biomedicine. The development of effective NPC-S materials has been hindered by the fusion of particles during the pyrolytic process that results in agglomerated materials with reduced activity. Herein, we present a process that enables the scalable synthesis of dispersed NPC-S materials by coating sacrificial protective layers around polyacrylonitrile nanoparticles (PAN NPs) to prevent interparticle cross-linking during carbonization. In a first step, PAN NPs are synthesized using miniemulsion polymerization, followed by grafting of 3-(triethoxysilyl)propyl methacrylate (TESPMA) to form well-defined core-shell structured PAN@PTESPMA nanospheres. The cross-linked PTESPMA brush layer suppresses cross-linking reactions during carbonization. Uniform NPC-S exhibiting diameters of ∼100 nm, with relatively high accessible surface area (∼424 m2/g), and high nitrogen content (14.8 wt %) was obtained. When compared to a regular nanoporous carbon monolith (NPC-M), the nitrogen-doped NPC-S demonstrated better performance for CO2 capture with a higher CO2/N2 selectivity, an increased efficiency in catalytic oxygen reduction reactions, as well as improved electrochemical capacitive behavior. This miniemulsion polymerization-based strategy for the preparation of functional PAN NPs provides a new, facile approach to prepare high-performance porous carbon spheres for diverse applications.

Onion-derived N, S self-doped carbon materials as highly efficient metal-free electrocatalysts for the oxygen reduction reaction

Abstract Onion-derived nitrogen, sulfur self-doped nanoporous carbon spheres (NSC) as efficient metal-free electrocatalyst were synthesized via a facile hydrothermal and subsequent pyrolysis process. The typical NSC with a high BET specific surface area of 1558 m 2 g −1 , contains 6.23 at.% N and 0.36 at.% S, and possesses high concentration of pyridinic and graphitic nitrogen species. Experimentally, the best performance was the NSC-A2 which showed excellent catalytic activity to oxygen reduction reaction via a 4 electron mechanism with an onset potential of 0.88 V (vs. RHE), and a superior stability comparable to commercial Pt/C catalyst. The high electrocatalytic activity is attributed to not only the synergistic effect of N and S dual doping in carbon and the sufficient active sites, but also its high BET specific surface area and suitable microporous structure. The results demonstrate that it is a simple and scalable approach for preparing efficient and low-cost carbon-based electrocatalysts for oxygen reduction reaction.

Sulfur-doped nanoporous carbon spheres with ultrahigh specific surface area and high electrochemical activity for supercapacitor

Development of facile and scalable synthesis process for the fabrication of nanoporous carbon materials with large specific surface areas, well-defined nanostructure, and high electrochemical activity is critical for the high performance energy storage applications. The key issue is the dedicated balance between the ultrahigh surface area and highly porous but interconnected nanostructure. Here, we demonstrate the fabrication of new sulfur doped nanoporous carbon sphere (S-NCS) with the ultrahigh surface area up to 3357 m2 g−1 via a high-temperature hydrothermal carbonization and subsequent KOH activation process. The as-prepared S-NCS which integrates the advantages of ultrahigh porous structure, well-defined nanospherical and modification of heteroatom displays excellent electrochemical performance. The best performance is obtained on S-NCS prepared by the hydrothermal carbonization of sublimed sulfur and glucose, S-NCS-4, reaching a high specific capacitance (405 F g−1 at a current density of 0.5 A g−1) and outstanding cycle stability. Moreover, the symmetric supercapacitor is assembled by S-NCS-4 displays a superior energy density of 53.5 Wh kg−1 at the power density of 74.2 W kg−1 in 1.0 M LiPF6 EC/DEC. The synthesis method is simple and scalable, providing a new route to prepare highly porous and heteroatom-doped nanoporous carbon spheres for high performance energy storage applications.

Current Trends in Designing and Applications of Nanoporous Carbon Spheres: A Mini Review

Current Trends in Designing and Applications of Nanoporous Carbon Spheres: A Mini Review

Role of porosity and polarity of nanoporous carbon spheres in adsorption applications

Structure-properties (i.e., porosity and polarity) of carbons are judiciously considered for the specific adsorption applications.

Alkali-assisted hydrothermal route to control submicron-sized nanoporous carbon spheres with uniform distribution

Carbon microspheres with nanoporous structures were synthesized based on hydrothermal reaction of saccharide solutions in the presence of potassium hydroxide. The influence of synthesis conditions, including types of saccharide, content of alkali, concentration and reaction time of saccharide solution, on the morphology of the microspheres was systematically investigated, with emphasis on controlling the microsphere size and understanding the role of alkali in hydrothermal reaction. The results show that the microspheres with regular spherical shapes and high surface areas around 500m2g−1 are obtained. The morphology of the microspheres can be tailored by changing the synthesis conditions. The mean diameter of the microspheres varies from 0.16 to 5.61μm. At different stages of the hydrothermal reaction of starch solution, alkali exhibits entirely different effects: (i) to slow the initial hydrolysis of starch, and (ii) to accelerate the subsequent polymerization of dehydrated and fragmented products and the growth of the microspheres. As a result, the competition between the hydrolysis kinetics and the polymerization and growth kinetics plays a critical role in the changes of the morphology and yield of the microspheres. The alkali in dilute starch solution (0.073–0.219M) promotes the increase of the size and yield of the microspheres. In contrast, the alkali in concentrated starch solution (0.292M) results in the reduction and the more uniform distribution of the size of the microspheres with almost constant yield. Note that this alkali assisted hydrothermal route can endow the microspheres with more surface functional groups, including hydroxyl and carboxyl groups, compared with the typical hydrothermal route without alkali. In addition, the formation of the stacks of graphene sheets and the decrease of functional groups occur in the microspheres during pyrolysis, which are accompanied by a significant weight loss of about 50% and a slight contraction in scale.

Molecular-based design and emerging applications of nanoporous carbon spheres.

Over the past decade, considerable progress has been made in the synthesis and applications of nanoporous carbon spheres ranging in size from nanometres to micrometres. This Review presents the primary techniques for preparing nanoporous carbon spheres and the seminal research that has inspired their development, presented potential applications and uncovered future challenges. First we provide an overview of the synthesis techniques, including the Stöber method and those based on templating, self-assembly, emulsion and hydrothermal carbonization, with special emphasis on the design and functionalization of nanoporous carbon spheres at the molecular level. Next, we cover the key applications of these spheres, including adsorption, catalysis, separation, energy storage and biomedicine — all of which might benefit from the regular geometry, good liquidity, tunable porosity and controllable particle-size distribution offered by nanoporous carbon spheres. Finally, we present the current challenges and opportunities in the development and commercial applications of nanoporous carbon spheres.

A simple CaCO3-assisted template carbonization method for producing nitrogen-containing nanoporous carbon spheres and its electrochemical improvement by the nitridation of azodicarbonamide

In this work, nitrogen-containing nanoporous carbon with spherical network structure have been prepared using a template carbonization method, in which diphenylguanidine serves as carbon precursor, commercially available CaCO3 as template, and azodicarbonamide as nitridation agent. All the obtained carbon materials exhibit the amorphous features with low graphitization degree. Besides, the nanoporous carbon materials show nanoscale spherical structures, probably due to the spherical structure of the CaCO3. The Carbon-DC sample exhibit a specific surface area of 652.3m2g−1, and a specific capacitance of 176.2Fg−1 at a current density of 1A g−1. Furthermore, the addition of azodicarbonamide which provide both carbon and nitrogen source can effectively tailor the properties of nanoporous carbon. The obtained Carbon-DCA sample contains as high as 12.45 at% of nitrogen has a specific surface areas of 1022.6m2g−1. As a result of the nitrogen content increased, the electrochemical performance is also significantly improved, with high specific capacitance (220Fg−1 in 6M KOH, 263F g−1 in 1M H2SO4) and excellent cycling stability after 5000 charge/discharge cycles. This template method provides a simple and inexpensive route to achieve nanoporous carbon for supercapacitor.

Supercapacitor performance of spherical nanoporous carbon obtained by a CaCO3-assisted template carbonization method from polytetrafluoroethene waste and the electrochemical enhancement by the nitridation of CO(NH2)2

How to properly dispose plastic wastes is still urgent and challenging for scientists nowadays. In this work, polytetrafluoroethene waste has been successfully converted into nanoporous carbon spheres by a simple template carbonization method, using CaCO3 as hard template. It is revealed that the carbonization temperature and the mass ratio of polytetrafluoroethene and CaCO3 play crucial roles in the determination of pore structures. The sample obtained with the ratio of polytetrafluoroethene-to-CaCO3 as 2:1 at 700°C, the carbon-2:1 sample, exhibits BET surface area of 646.3m2g−1, and pore volume of 0.65cm3g−1. The resulting specific capacitance is 179.9F g−1 when measured at 1Ag−1 in a three-electrode system, using 6molL−1 KOH as electrolyte. Next, to modify the pore structures as well as the resultant electrochemical behaviors, CO(NH2)2 has been added to make the carbon matrix nitrogen-containing. The sample produced with the mass ratio of polytetrafluoroethene, CaCO3 and CO(NH2)2 as 2:1:2 at 700°C, the carbon-2:1:2 sample, exhibits BET surface area of 1048.2m2g−1, and pore volume of 1.03cm3g−1. As a consequence, its specific capacitance has been improved to be 237.8Fg−1 at 1Ag−1. The present CaCO3-assisted template carbonization method is simple, reproducible and scalable and can be readily extended to treat with other halogen-containing plastic wastes.