Porous Carbon Spheres Research Articles

An interfacial self-assembly strategy to fabricate graphitic hollow porous carbon spheres for supercapacitor electrodes

Graphitic hollow porous carbon spheres (GHPCSs) have the advantages of a unique cavity structure, high surface area and excellent conductivity, and are promising electrode materials for energy storage. A Fe–tannic acid (TA) framework synthesized using TA as the carbon source and K3[Fe(C2O4)3] as a complexing agent, was self-assembled onto a melamine foam, which was converted to GHPCSs by carbonization, where the K3[Fe(C2O4) 3] also acts as an activating-graphitizing agent. The outer shell of the as-prepared GHPCSs has a large specific surface area, a micropore-dominated structure and excellent electrical conductivity, which ensure a large enough active surface area for charge accumulation and fast ion/electron transport in the partially graphitized carbon framework and pores. The optimum GHPCS has a high capacitance of 332.7 F g−1 at 1 A g−1. An assembled symmetric supercapacitor has a high energy density of 23.7 Wh kg−1 at 459.1 W kg−1 in 1 mol L-1 Na2SO4. In addition, the device has long-term cycling stability with a 92.1% retention rate after 10,000 cycles. This study not only provides an economic and time-saving approach for constructing GHPCSs by a self-assembly method, but also optimizes ion/electron transport in the carbon spheres to give them excellent performance in capacitive energy storage.

Phosphorus and Oxygen Dual‐Doped Porous Carbon Spheres with Enhanced Reaction Kinetics as Anode Materials for High‐Performance Potassium‐Ion Hybrid Capacitors

AbstractHard carbons with low cost and high specific capacity hold great potential as anode materials for potassium‐based energy storage. However, their sluggish reaction kinetics and inevitable volume expansion degrade their electrochemical performance. Through rational nanostructure design and a heteroatom doping strategy, herein, the synthesis of phosphorus/oxygen dual‐doped porous carbon spheres is reported, which possess expanded interlayer distances, abundant redox active sites, and oxygen‐rich defects. The as‐developed battery‐type anode material shows high discharge capacity (401 mAh g−1 at 0.1 A g−1), outstanding rate capability, and ultralong cycling stability (89.8% after 10 000 cycles). In situ Raman spectroscopy and density functional theory calculations further confirm that the formation of PC and PO/POH bonds not only improves structural stability, but also contributes to a rapid surface‐controlled potassium adsorption process. As a proof of concept, a potassium‐ion hybrid capacitor is assembled by a dual‐doped porous carbon sphere anode and an activated carbon cathode. It shows superior electrochemical performance, which opens a new avenue to innovative potassium‐based energy storage technology.

Capacitive deionization of carbon spheres with a carbon shell derived from the quantum dots of urea-citric acid grown in situ

Limited by the cost of electrode materials with a pore structure designed, there is an urgent need to prepare a low-cost carbon material with a strong salt absorption capacity (SAC) for capacitive deionization (CDI) to produce fresh water at an affordable price. The preparation of core-shell porous carbon spheres (CSs) derived from the melamine-formaldehyde (MF) spheres with a urea-citric acid quantum dot (UCQD) layer grown in situ has been reported here. Benefiting from their large specific surface area (2667.44 m2·g−1) and the uniformly doped nitrogen atoms (1.03 at.%), the prepared CSs have abundant active sites for ion absorption. Their SAC reaches up to 19.80 mg·g−1 in the NaCl solution of 1000 mg·L−1 with a working voltage of 1.2 V. Moreover, no SAC attenuation occurs after 17 cycles. This work provides a possible way to prepare low-cost core-shell CSs for CDI.

Sustainable porous hollow carbon spheres with high specific surface area derived from Kraft lignin

Hollow carbon spheres (HCSs) have attracted tremendous interest in recent years due to their intriguing structure-induced physicochemical properties and significant potential for numerous applications. However, the preparation of HCSs with precise structural control using a simple and scalable strategy remains challenging. In this work, hollow carbon particles having a well-defined spherical morphology were successfully produced using a green, economical, and facile spray drying method together with a carbonization process. Kraft lignin was employed as the carbon precursor in place of lignosulfonate with potassium hydroxide (KOH) as an activation agent. The high specific surface area (1536.5–2424.8 m2 g−1) with micro-mesoporous structure of HCSs can be easily tuned by controlling the mass ratio of KOH to carbon precursor. The KOH-to-lignin mass ratios were utilized below 1.5, lower than those in previous studies typically used higher than 3, which was in accordance with green chemistry principles. In addition, these HCSs have applications as electrode materials in supercapacitors for energy storage devices. With the great achievements and continuous efforts in this important field, these results suggest that our approach will open a new path for the development of advanced carbon materials and high value-added utilization of Kraft lignin as a promising material for potential applications.

Facilitating redox kinetics of sulfur species by cobalt-nitrogen co-doped porous hollow carbon for high-performance Li-S battery

The shuttle effect of polysulfides is the main obstacle restricting the development of lithium-sulfur batteries. However, most efforts focused on physical adsorption and polar adsorption cannot fundamentally solve the problem of sluggish conversion of polysulfides, especially for high sulfur loading. Herein, a cobalt-nitrogen co-doped porous hollow carbon sphere (Co-CN) is synthesized in one step. The porous conductive carbon spheres can realize a rapid charge transfer, mitigate volume expansion during cycling and enhanced physical adsorption for polysulfides. Nitrogen and cobalt doping provide chemisorption and catalysis for the restriction and conversion of polysulfides. Furthermore, liquid Li2S8 polysulfide was used as sulfur source to guarantee high sulfur loading and fast redox kinetic. Benefiting from the triple effect of physical adsorption, chemical adsorption and catalysis, the Co-CN@Li2S8 cell with sulfur loading of 5.15 mg cm−2 delivers a high reversible initial capacity of 1499 mAhg−1 at 0.1C and 880.9 mAhg−1 after 100 cycles. More excitingly, the capacity decay rate was only 0.012% per cycle at 1C over 1000 cycles, indicating excellent long cycle stability. This work provides a facile and effective route for Co-CN as a sulfur host in lithium-sulfur battery.

Fabrication of S,N-Doped Carbon-Coated SnS2/SnS Heterostructures Supported by Hollow Carbon Microspheres for Sodium-Ion Storage

Developing novel anode materials containing electroactive heterostructures which boost ion and charge transfer kinetics in a carbon matrix is still a great challenge. Here we report on a new smartly designed material: SnS2/SnS p-n heterostructures embedded in S,N-doped carbon layer supported by hollow carbon spheres (C@SnSx@C) by a facile method and applied as negative electrode material in sodium ion batteries. The C@SnSx@C2 (at optimized carbon ratio) negative electrode can deliver an initial reversible capacity of 636.5 mAh·g−1 at 0.1 A·g−1, superior rate capability (265.1 mAh·g−1 at rate of 10.0 A·g−1) and long cycle life (capacity retention of 96.3 % at 1.0 A·g−1 after 150 cycles). The SnS2/SnS p-n heterojunctions provide a lower sodium ion diffusion energy barrier (0.38 eV), higher Na+ adsorption energy (−4.66 eV) and higher electronic conductivity due to an internal electric field according to density functional theory calculations compared to plain SnS. Moreover, S,N-doped carbon facilitates electronic conductivity and buffers the volume changes during the conversion reaction-based SnSx upon sodium insertion and extraction process. Porous hollow carbon spheres contribute to prevent the agglomeration of SnS2/SnS nanosheets and keep the structural integrity. Our findings on this unique material might be extended to other ion battery technologies.

Preparation and properties of transition metal nitrides caged in N-doped hollow porous carbon sphere for oxygen reduction reaction

A series of transition metal nitrides (MxNy, M=Fe, Co, Ni) nanoparticle (NP) composites caged in N-doped hollow porous carbon sphere (NHPCS) were prepared by impregnation and heat treatment methods. These composites combine the high catalytic activity of nitrides and the high-efficiency mass transfer characteristics of NHPCS. The oxygen reduction reaction results indicate that Fe2N/NHPCS has the synergistic catalytic performance of higher onset potential (0.96 V), higher electron transfer number (~4) and higher limited current density (1.4 times as high as that of commercial Pt/C). In addition, this material is implemented as the air catalyst for zinc-air battery that exhibits considerable specific capacity (795.1 mA·h/g) comparable to that of Pt/C, higher durability and maximum power density (173.1 mW/cm2).

A liquid marble method for synthesizing large-sized carbon microspheres with controlled interior structures

Millimeter-sized porous carbon spheres (MPCS) with both controllable interior architecture and high mechanical strength are highly desired for practical applications, but there is no efficient method to synthesize these materials. Here, we report a strategy to fabricate millimeter-sized porous carbon spheres by harnessing the liquid marble phenomenon. This strategy enables us to obtain a series of MPCS with tunable interior architectures, such as honeycombed MPCS, foam-like MPCS, cavity-containing MPCS and hollow MPCS, which add new members to carbon microsphere family. Crucially, the mechanical strength of MPCS reaches as high as 14.6 N, favoring its practical applications. Moreover, our protocol allows for nitrogen element and metal to be in situ incorporated within the body of MPCS, leading to an efficient catalyst for levulinic acid (LA) hydrogenation or benzene hydrogenation. Impressively, turnover numbers (TONs) of 113000 in the LA hydrogenation and 480 h of continuous benzene hydrogenation with TONs of 116000 are achieved, which highlights the potential in engineering applications of these novel microspheres.

Porous carbon spheres anode with the stable output of low delithiation plateau and constant delithiation ratio for lithium ion hybrid capacitor

Porous carbon spheres derived from the facile hydrothermal treatment associated with the calcination process exhibit the good spherical morphology and unique porous structure. For the Li-based half-cell test, porous carbon spheres electrode not only exhibits larger reversible capacities and better compatibility as compared to the widely-used graphite, but also provides stable delithiation plateaus under different current density. Additionally, the delithiation ratio below 1V almost accounts for a constant value (around 70%) with the increase of current density, evidencing that Li intercalation storage is the dominant model and Li insertion/extraction processes are propitious. The lithium ion hybrid capacitor configured with S-doped mesoporous graphene and porous carbon spheres as cathode and anode, delivers satisfied energy and power densities (up to 177Whkg−1 and 12,303Wkg−1, respectively) as well as long-term cyclability, which is superior to the corresponding S-doped mesoporous graphene//graphite and activated carbon//porous carbon spheres. In addition, the developed synthesis strategy is in favor of the realization of the scalable production of porous carbon spheres.

Efficient oxygen reduction reaction by a highly porous, nitrogen-doped carbon sphere electrocatalyst through space confinement effect in nanopores

A highly porous nitrogen-doped carbon sphere (NPC) electrocatalyst was prepared through the carbonization of biomass carbon spheres mixed with urea and zinc chloride in N2 atmosphere. The sample carbonized at 1000 °C demonstrates a superior oxygen reduction reaction (ORR) performance over the Pt/C electrocatalyst, while its contents of pyridinic nitrogen and graphitic nitrogen are the lowest among samples synthesized at the same or lower carbonization temperatures. This unusual result is explained by a space confinement effect from the microporous and mesoporous structures in the microflakes, which induces the further reduction of peroxide ions or other oxygen species produced in the first step reduction to water to have the preferred overall four electron reduction ORR process. This work demonstrates that in addition to the amount or species of its active sites, the space confinement can be a new approach to enhance the ORR performance of precious-metal-free, nitrogen-doped carbon electrocatalysts.

Structure engineering in interconnected porous hollow carbon spheres with superior rate capability for supercapacitors and lithium-sulfur batteries

The application of hollow carbon spheres in energy storage devices is still hindered by their relatively low electron transmission and ion diffusion kinetics, as well as their insufficient storage sites. Herein, we prepare interconnected porous honeycomb hollow carbon spheres (IPHHCSs) using hard-templating route by increasing the concentration of template spheres and introducing cationic surfactants simultaneously. The as-obtained IPHHCSs show favorable features for ESD, such as large contacted areas between spheres, high specific surface areas (951 m2 g−1), hierarchical porous frameworks with high volume of mesopores, and rich N-doping (3.36%), achieving a lower interface-resistance between spheres, more ion-storage sites, and developed mesoporous channels for rapid ions diffusion. Thus, such a unique carbon architecture endows IPHHCSs a superior rate capability for supercapacitor and lithium-sulfur battery applications. The IPHHCSs supercapacitor’s electrode delivers a high specific capacitance of 295F g−1 at 1 A g−1, an outstanding rate capability (87% capacitance retention from 1 A g−1 to 20 A g−1), with a high cycling life stability (1.2% loss after 10,000 cycles). As for lithium-sulfur batteries, the IPHHCSs/S cathode with sulfur loading of 70% demonstrated an initial reversible capacity of 1160 mAh g−1 at 0.2C and an excellent rate performance with a capacity retention of 53% at 10C. More notably, IPHHCSs/S electrode could also enable a remarkable cyclic stability that possesses a reversible capacity of 285 mAh g−1 at 10C upon 1000 cycles with a low capacity degradation of 0.042% per cycle. Controllable design of interconnected porous HCSs structures could decrease interface-resistance and promote ion diffusion, which can be an effective way for developing high-rate supercapacitors and Li–S batteries.

Efficient adsorption-reduction synergistic effects of sulfur, nitrogen and oxygen heteroatom co-doped porous carbon spheres for chromium(VI) removal

The S,N,O-co-doped porous carbon spheres, derived from starch with plentiful oxygen-containing functional groups, acted as an effective adsorbent for the removal of hexavalent chromium (Cr(VI)) from wastewater. The abundant surface functional groups of carbon spheres significantly improved the Cr(VI) adsorption by synergistic effect of multiple functional groups. Meanwhile, these reductive functional groups (such as C-SH, -NH-, C-H and C-OH) could serve as electron donors to efficiently reduce the adsorbed Cr(VI) into Cr(III). Benefiting from the cooperation between adsorption and reduction mechanism of Cr(VI), the S,N,O-co-doped of porous carbon spheres with high specific surface area of 2617 m2/g, exhibited superior efficiency for Cr(VI) removal at 97% and the maximum adsorption capacity could reach 434 mg/g at 298 K.

Multiple-loss-enhanced NiOx@carbon spheres/reduced graphene oxide-based composite for tuneable elimination of electromagnetic signals

In this work, a novel graphene-based ternary composite NiOx@CS/reduced graphene oxide (rGO) consisting of magnetic nanoparticles (NiOx) and porous carbon spheres (CS) were successfully synthesised through facile hydrothermal and high-temperature sintering approaches. Owing to the ternary structure, the dielectric and magnetic capacity of the composite was improved. Further, the synergistic effect of two loss mechanisms improves the absorption efficiency of electromagnetic waves. The maximum reflection loss of NiOx@CS/rGO-20 wt% was −69.3 dB at 7.2 GHz and the absorption bandwidth with reflection loss below −10 dB was 4.04 GHz (6.36–10.4 GHz). Hence, the NiOx@CS/rGO ternary composite with a combination of dielectric and magnetic loss-facilitated absorption provides a new design paradigm for tuneable elimination of electromagnetic signals.

Porous Carbon Spheres with Ultra-fine Fe2N Active Phase for Efficient Electrocatalytic Oxygen Reduction

In this work, hierarchically porous carbon spheres co-doped by iron and nitrogen were synthesized via in situ dehalogenation. The rich porous structure and relatively high specific surface area (210 m2/g) facilitate the formation of an ultra-fine Fe2N active phase and FeN4 active centers within the carbon matrix. Transmission electron microscopy and X-ray photoelectron spectroscopy analysis further reveal the presence of a dominant Fe2N phase and minor FeN4 bonds in the as-prepared Fe-N-C-pd-800 samples. Because of this, the oxygen reduction reaction (ORR) process can more readily take place on Fe2N than on FeN4, and the Fe2N phase enriched Fe-N-C-pd-800 carbon spheres exhibit a promising onset potential (Eonset=1.02 V) and half-wave potential (E1/2=0.86 V) in alkaline media. In addition, Fe-N-C-pd-800 also shows excellent methanol resistance and long-cycling stability.

Well-dispersed pyrite-type RuS2 nanocrystals anchored on porous nitrogen and sulfur co-doped hollow carbon spheres for enhanced alkaline hydrogen evolution

The hydrogen evolution reaction (HER) activity in alkaline condition is generally suppressed due to sluggish water dissociation–related Volmer process. Consequently, developing new highly-active and cost-efficient electrocatalysts for the alkaline hydrogen production is greatly desirable for achieving sustainable water splitting in industrial plants. Pyrite-type RuS2 is a potential excellent electrocatalyst for alkaline HER but the related research is still in its infancy. Herein, well-dispersed crystalline RuS2 nanoparticles (c-RuS2 NPs) with ultrasmall particle size anchored on porous nitrogen and sulfur co-doped hollow carbon spheres (NSC) are synthesized for alkaline HER electrocatalysis. The conductive and porous hollow carbon spheres with nitrogen and sulfur doping is used as the effective support to provide abundant anchoring sites and modify the electronic structure of RuS2, beneficial to increasing the active sites and improving the intrinsic activity. Furthermore, the crystallinity modulation of ruthenium sulfide also has a significant impact on HER activity. In 1.0 M KOH solution, the proposed c-RuS2 NPs/NSC catalyst exhibits admirable activity for HER electrocatalysis with a low overpotential of 11 mV at a current density of 10 mA cm−2 and a small Tafel slope of 35.4 mV dec−1. With low Ru loading, superior hydrogen evolution in alkaline media is achieved for c-RuS2 NPs/NSC compared to the commercial Pt/C and the reported ruthenium-sulfide-based electrocatalysts.

Beyond hierarchical mixed nickel-cobalt hydroxide and ferric oxide formation onto the green carbons for energy storage applications

To attain superior energy density concurrently with high power density, high-performance supercapacitors have been developed. Herein an innovative strategy has been adopted to fabricate unique binder-free electrodes composed of a unique porous structure of binary metal carbonate hydroxide nanomace-decorated hydrothermal porous carbon spheres (PCSs). Hierarchical nickel-cobalt carbonate hydroxide (NiCOCH) nanomaces, directly grown on PCSs, are used as positive electrodes for supercapacitors fabrication. Furthermore, Fe2O3@PCS composites, having benefits of highly reversible redox reaction in the negative potential window and highly porous structure, are employed as the negative electrode in the fabrication of the asymmetric supercapacitors (ASCs). The assembled NiCoCH@PCS// Fe2O3@PCS asymmetric devices with a wide electrochemical potential window not only have the merit of high energy and power densities but also receive benefits from remarkable cycle stability. These encouraging outcomes that are mutually beneficial, make these fabricated ASCs significantly ideal for high-performance electronics.

Molecular Level Design of Nitrogen-Doped Well-Defined Microporous Carbon Spheres for Selective Adsorption and Electrocatalysis.

Nitrogen-doped porous carbon spheres have attracted great interest in diversified fields owing to their unique physical and chemical properties. However, the synthesis of nitrogen-doped porous carbon spheres with hierarchical superstructures and refined micropore structures is still a challenge. Herein, we develop a molecular-scale silica templating strategy to prepare nitrogen-doped microporous carbon spheres (MCSSs) with high porosity and a well-defined micropore structure. Octa(aminophenyl) polyhedral oligomeric silsesquioxane is used as a building block in MCSS precursors to provide precise molecular-scale templating and nitrogen doping. The morphology of MCSSs can be easily tuned by choosing the proper solvent. The as-synthesized MCSS with a large surface area (2036 m2 g-1), narrow micropore size distribution, nitrogen doping, and hierarchical geometry can serve as an efficient selective adsorbent for CO2 and organic pollutants. Furthermore, the MCSS decorated with Fe-N-C active sites (MCSS-Fe) shows enhanced electrocatalytic ORR activity in alkaline solution. This novel approach may open a new avenue for controllable fabrication of porous carbon spheres with desired geometry and well-designed pore structure and show potential applications in selective adsorption and catalysis.

Elucidating influence of the existence formation of anchored cobalt phthalocyanine on electrocatalytic CO2-to-CO conversion

Heterogeneous molecular catalysts with inexpensive transition-metal centers have attracted much attention, due to their excellent electrocatalytic performance on electrocatalytic carbon dioxide reduction reaction (CO 2 RR). Among them, metal phthalocyanine (MePc) has aroused great interest. However, the complex existence formation (crystals or evenly dispersion) in the hybrid catalyst, e.g. cobalt (II) phthalocyanine (CoPc), determining the final electrocatalytic CO 2 RR performance still remains debate. To further elucidate the influence of the existence formation of CoPc on electrocatalytic performance of CO 2 -to-CO conversion, we synthesized ultra-thin nitrogen-doped hollow carbon spheres (N-doped HCS) with a high surface area of 653.3 m 2 g −1 as the support to anchor a series of different existence formation of CoPc. The existence formation of CoPc in the hybrid catalyst is closely related with the content of Co atom, the latter of which is the key factor of the CO 2 RR performance. We summarized the nonlinear relationship between the partial CO current density ( j CO ) and the content of Co atom at −0.82 V vs. RHE, and the equation of Faraday efficiency of CO ( FE CO ) vs. the content of Co atom at −0.82 V vs. RHE, which proves the fact that the coexistence of crystals and evenly dispersed CoPc or evenly dispersed and low loading of CoPc both could reach the satisfying results ( j CO > ~14 mA cm −2 , FE CO > ~ 91%, at −0.82 V vs. RHE) under the content of Co atom from 1.26 wt% to 0.14 wt%. The optimal catalyst (Co, 0.49 wt%) achieved a near-unity Faradaic efficiency of 96%, which is close to 4 times that of the unsupported CoPc ( FE CO =24.54%), and an outstanding current density of 20.47 mA cm −2 towards CO, which is c.a. 60 times higher than that of the unsupported CoPc (0.34 mA cm −2 ) at −0.82 V vs. RHE. This work could potentially inspire the rational design of heterogeneous molecular catalysts and promote its application in the energy conversion and storage field. The nitrogen-doped porous hollow carbon spheres anchor a series of cobalt phthalocyanine for electrocatalytic carbon dioxide reduction. • Different amount of Cobalt (II) phthalocyanine (CoPc) is immobilized on N-doped HCS as electrocatalysts. • Their electrochemical CO 2 RR properties were found to be closely related with the existence formation of CoPc. • The nonlinear relationship of existence formation of CoPc and electrocatalytic performance is discussed and elucidated. • Optimized catalyst is enumerated with excellent value of multiparameters. • The mechanism of electroreduction CO 2 -to-CO conversion is deduced for better understanding.

Metal-organic framework precursors derived Ni-doping porous carbon spheres for sensitive electrochemical detection of acetaminophen

The sensitive and selective determination of acetaminophen (AP) in the human body is highly desirable to ensure human health. In this work, nickel-doping nanoporous carbon (Ni/C) was fabricated by directly calcining Ni based metal-organic framework (Ni-MOF). The Ni/C based electrochemical sensor was developed for sensitive and selective determination of AP in human blood serum and urine samples. The prepared Ni/C composite possess plentiful catalytic active sites, ordered mesoporous structure and large specific surface area, which endow the constructed Ni/C sensor with a prominent performance for acetaminophen sensing. Under the optimal conditions, the developed method offered good linearity in the range of 0.20–53.75 μM with a low detection limit (S/N = 3) of 4.04 × 10−2 μM. The electrocatalytic performance of the sensor towards AP was further measured by differential pulse voltammetry and cyclic voltammetry. The results demonstrated that the Ni/C sensor can be feasibly employed for the determination of AP in human blood serum and urine samples with excellent anti-interference stability and good reproducibility. The research reveals a great promising of the Ni/C electrochemical sensor for clinical applications and paves a way for the construction of high-performance electrochemical sensors for AP determination.

Confining Sulfur in N‐Doped Hollow Porous Carbon Spheres for Improved Lithium‐Sulfur Batteries

AbstractRationally designing sulfur host which allows fast redox kinetics and can confine soluble polysulfides (PSs) is crucial for high‐performance lithium‐sulfur batteries (LSBs). Herein, N‐doped hollow porous carbon spheres (NHPCS) with large specific surface area (1526 m2 g−1) and strong interaction toward PSs were fabricated by a template method and applied as an efficient sulfur host. Benefiting from the hollow porous structure and function design, the NHPCS shows a high sulfur loading of 78.9 wt.% and improved adsorption capacity for PSs. Finally, the LSBs with the S@NHPCS as the cathode exhibit higher initial capacity of 1263 mAh g−1 at 0.2 C and lower decay rate (0.07 % per cycle) than S@CNT after 500 cycles at 1 C.