Hollow Carbon Spheres Research Articles

A candy-like photocatalyst by wrapping Co, N-co-doped hollow carbon sphere with ultrathin mesoporous carbon nitride for boosted photocatalytic hydrogen evolution

Hierarchical carbon material is used as a star cocatalyst in the field of photocatalysis due to its excellent catalytic properties. In this work, mesoporous carbon nitride sheet (MCNS) photocatalyst introduced nitrogen-doped hollow carbon spheres assembled with cobalt nanoparticles (Co@NHC) is synthesized by electrostatic adsorption. A series of characterizations are analyzed to display the structures, morphologies and optical properties of as-prepared materials. The photocatalytic activity of Co@NHC/MCNS material is evaluated with hydrogen evolution under visible light irradiation. The results indicate that 5 wt% Co@NHC/MCNS material reveals higher photocatalytic activity of hydrogen evolution rate of 3675 µmol/g with 4 h reaction time, which is 159 times than that of pure MCNS material. The carbon material with excellent charge transport properties can effectively accelerate the charge transfer from ultrathin MCNS to cobalt nanoparticles. The goal of improving the photocatalytic performance of Co@NHC/MCNS material is achieved. As a result, it provides a feasible and promised approach for doping transition metals to enhance photocatalytic activity.

Hierarchical core-shell nickel hydroxide@nitrogen-doped hollow carbon spheres composite for high-performance hybrid supercapacitor

Designing electrode materials with high performance and maximum utilization is of great desire for supercapacitors, which highly depend on the intrinsic electrochemical properties and the optimal frameworks of the electrode materials. The hierarchical core-shell structure with various types of pores can make the most of the electrode material due to the easy access of electrolyte into the interior electrode and large exposure of electrode into the electrolyte. In this work, nickel hydroxide@nitrogen-doped hollow carbon spheres (Ni(OH)2@NHCSs) electrode material with a hierarchical core-shell structure was obtained using a hard template and the following chemical-precipitation method. Ni(OH)2@NHCSs electrode displays an excellent specific capacity of 214.8 mA h g−1 (that is 1546.6 F g−1), higher than the Ni(OH)2 counterpart (108.9 mA h g−1, that is 784.1 F g−1) at 1 A g−1 in 2 M KOH electrolyte. The assembled Ni(OH)2@NHCSs||NHCSs hybrid supercapacitor (HSC) delivers an energy density of 37.5 W h kg−1 at 800.0 W kg−1 and an outstanding stability with 79.2% of retention rate for 10,000 cycles at a current density of 8 A g−1. The Ni(OH)2@NHCSs electrode exhibits excellent electrochemical performance primarily contributed by its unique hierarchical core-shell structure, high specific surface area and enhanced electrical conductivity.

Template-free strategy for constructing polyaniline/polypyrrole derived carbon sphere as supercapacitors electrode use in acidic and alkaline electrolytes

Undesirable energy density and storage ability hinder the pure carbon-based symmetric supercapacitor commercial application. Constructing hierarchical pore structure carbon material is expected to overcome this challenging issue. How to effectively reduce the multi-step and improve efficiency is worthy of in-depth study. Herein, a template-free strategy is proposed to construct N-doped hollow carbon sphere, combining a pore-forming agent and alkali treatment to build a hierarchical pore structure. Investigating the various pore structure contents in carbon spheres reveals its effect on the capacitive performance of as-prepared samples. From the robust walls structure (~50 nm) and rational micropores proportion (68.3 %), HCZK carbon sphere is equipped with a specific capacitance of 550.6 and 273.3 F g−1 in acidic and alkaline electrolyte, respectively, at a current density of 1 A g−1. After 10,000 cycles charge/discharge test, the specific capacitance of HCZK sample does not lose in acidic electrolyte, and 4.1 % in alkali electrolyte. Symmetric supercapacitors assembled by HCZK carbon sphere deliver a specific capacitance of 247.1 F g−1 at 1 A g−1, outstanding coulombic efficiency of 100 % after 10,000 cycles and excellent energy density of 87.8 Wh kg−1 at a power density of 1288.0 W kg−1. Achieve the above excellent properties can be attributed to the synergistic effect of rational pore structure and surface chemical composition. This work will reveal the contribution of micropores to the electrochemical of carbon materials and provide a reference for selecting electrolytes.

Sacrificial template induced Fe-, N-, and S-tridoped hollow carbon sphere as a highly efficient electrocatalyst for oxygen reduction reaction

Developing electrocatalysts free from precious metals for oxygen reduction reaction (ORR) is essential for clean energy storage and conversion systems such as metal-air batteries and fuel cells. Herein, hollow-structured Fe-, N-, and S-tridoped carbon (FeNSC) spheres were synthesized by hydrothermal polymerization of polypyrrole, impregnation of iron species, pyrolysis, and a sulfidation processes. During the synthesis procedure, SiO2 nanospheres were used as self-sacrificial templates to achieve a uniform hollow structure. The electronic structure of the highly active Fe–N site was modified by sulfur dopants with relatively low electronegativity, thus efficiently enhancing ORR kinetics. The hollow-structured FeNSC nanospheres exhibited excellent electrocatalytic performance toward the ORR in an alkaline electrolyte, with a remarkable onset potential (0.971 V vs. RHE) and half-wave potential (0.877 V vs. RHE), even outperforming state-of-the-art Pt/C (0.977 and 0.858 V vs. RHE). Furthermore, the FeNSC hollow spheres showed outstanding electrochemical stability over 100 h and methanol tolerance against commercial Pt/C. The findings of this study provide novel insights for designing precious metal-free electrocatalysts with unique hollow structures and heteroatom-doped carbon for energy storage and conversion.

Ultralong cycle life and high rate sodium-ion batteries enabled by surface-dominated storage of 3D hollow carbon spheres

Carbon materials are considered as prospective candidates for Na-ion batteries (SIBs) anodes, which have attracted significant attention. It is critical to develop a novel carbon anode with high specific capacity and excellent coulombic efficiency for practical application of SIBs. Herein, N/S-codoped hollow carbon spheres with rich carbon nanotubes is developed to work as sodium ion batteries anode. Owing to the unique structure, the material exhibits excellent performance and cycling stability at ultrahigh rate. In addition, the capacity maintains at 130 mA h g-1 under a current density of 10 A g-1 after 5600 cycles. The mechanisms of surface-dominated storage are elaborated by electrochemical test, scanning transmission electron microscopy, X-ray photoelectron spectroscopy, Raman analysis, ex situ X-ray diffraction. Furthermore, we quantitatively calculate the relationship between the extra specific capacity and the introduced defect, which can give the inspiration of improving the performance of sodium ion batteries. These results benefit the development of novel excellent sodium storage materials.

Catalytic oxidation of pentanethiol on basic nitrogen doped carbon hollow spheres derived from waste tires

A series of basic nitrogen doped carbon hollow spheres (p-N-C) catalysts derived from waste tires were prepared by a green, facile and environmental “leavening” strategy for the catalytic oxidation of pentanethiol. Compared to pristine carbon, the p-N-C has a higher surface curvature conducive to the enrichment of substrates, leading to an excellent catalytic performance. This increased surface curvature of p-N-C was fabricated on the synergistic effect of two foaming agents ((NH4)2C2O4 and NaHCO3), and the released gas also endows the spherical shell of p-N-C with a hierarchical porous structure, promoting the accessibility of active sites with pentanethiol. Pyridine-like and pyrrolic-like nitrogen atoms were investigated as reactive sites on the p-N-C to accelerate the electron transfer from sulfur to active surface oxygen and enhance the adsorption/oxidation process. As a result, the optimal p-N-C catalyst exhibits superior adsorption and oxidation performance (99.9%) of pentanethiol, outperforming the “unleavened” catalyst (20.8%). This work offers a new avenue for the fabrication of highly efficient materials for the desulfurization of fuel.

Devising a universal tailored monomer molecular strategy for SiOx/carbon hollow spheres as a synergistic electrocatalyst in azathioprine sensing

Designing hollow spheres (HS) structures of polymer materials with uniformly dispersed SiOx and surface attributes is currently attracting much attention due to their vital roles in catalysis and energy storage applications. Instances of their compilation exist, but such morphological scaffolds require easy yet versatile conceptual approaches. Despite the easy yet controllable assembly of uniformly adorned SiOx and carbon HS (C-HS), producing copious voids simultaneously through a one-step reaction still remains a major challenge. In this study, an ultrafast additive and template-free molecular polymerization strategy were designed to fabricate uniformly dispersed SiOx/C-HS for electrocatalysis. Dual-aldehydes and (3-aminopropyl)triethoxysilane (APTES) were judiciously designed as C and silicon precursors to yield the polymer HS (P-HS) via a simple one-step aldimine condensation. Two different P-HS morphologies were obtained utilizing glyoxal (GL) and glutaraldehyde (GA) as the cross-linkers, proving the great tunability of the methodology. Prominently, in situ carbonization of the P-HS guarantees the uniform integration of SiOx in C-HS at a nanoscale range. As an example of the application of the synthesized P-HS and SiOx/C-HS, the electrochemical performance for azathioprine (AZP) detection was tested. Benefiting from high conductivity, large surface area, and fast electron transfer due to the well-dispersed SiOx in the C-HS substrate surface, the resultant SiOx/C-GA modified electrode showed a low limit of detection (2.26 nM), high sensitivity (4.26 μA μM-1cm-2) and good repeatability and reproducibility for AZP detection. Detection was also validated in actual samples. The strategy adopted, not only implements Si-based C-HS composites as efficient and scalable electrode materials but also paves the way toward a new platform for the synthesis of additive and template-free HS.

Porous Carbon@Ferric Silicate Hollow Spheres for Enhanced Lithium and Sodium Storage

The intrinsic poor conductivity and large volume variation of ferric silicate severely hinder its practical application. Herein, a unique double‐shell‐structured amorphous porous carbon@ferric silicate hierarchical hollow sphere (PC@FS) is designed to improve its electrochemical performance. The amorphous feature of PC@FS is favorable for Li+/Na+ diffusion and avoids the structure collapse. FS nanosheets shorten the transport path of lithium/sodium ions. The hollow carbon spheres not only boost the conductivity but also accommodate volume variation. Besides, the heterointerface of PC@FS exhibits interfacial lithium/sodium storage. The synergistic effects bestow PC@FS enhanced lithium and sodium storage with high reversible capacity, excellent rate performance, and remarkable cycling stability. It manifests a capacity as high as 625.7 mAh g−1 at 5 A g−1 after 1000 cycles for lithium‐ion batteries and 315.7 mAh g−1 at 0.05 A g−1 after 50 cycles for sodium‐ion batteries.

Ethanol gas sensing with lower temperature and higher response based on three-dimensional multilevel materials composed of micron hollow carbon spheres@SnO2 nanoparticles

Metal oxide semiconductor gas sensors (MOS) based on tin oxide have excellent performance in ethanol gas detection and have been widely used in industrial production, environmental protection, and road safety detection. However, conventional tin oxide sensors can only show excellent detection performance for ethanol gas above 250 °C. In this work, nano-size tin oxide particles were grown on the micron hollow carbon spheres derived from the biomaterial chlorella by a gel method. This three-dimensional hierarchical porous structure can enrich ethanol gas at a certain temperature. Ethanol gas sensor fabricated with this material has better sensing performance at low temperature (168–200 °C).

Morphology-Controlled Fabrication Strategy of Hollow Mesoporous Carbon Spheres@f-Fe2O3 for Microwave Absorption and Infrared Stealth.

The design and development of radar--infrared compatible stealth materials are challenging in the field of broadband absorption due to the contradiction of stealth requirements and mechanisms in different frequency bands. However, hollow structures show great promise for multispectral stealth because they can lengthen the attenuation path of electromagnetic waves (EMWs) for microwave absorption, interrupt the continuity of heat-transport channels, and lower the thermal conductivity to realize infrared stealth. Here, a new morphological fabrication strategy has been developed to efficiently prepare compatible stealth nanomaterials. In a specific hydrothermal process, the confined growth of flake α-Fe2O3 (f-Fe2O3) outside of hollow mesoporous carbon spheres (HMCS) is achieved using NH3·H2O as a shape-controlled reagent. The introduction of f-Fe2O3 helps to lower infrared emissivity and improve high-frequency impedance matching, which depends on the stable dielectric property of the specific flake shape. Moreover, the size of f-Fe2O3 can be regulated by changing the constituent proportion in the hydrothermal suspension to obtain excellent performance. The minimum reflection loss (RL) of the HMCS@f-Fe2O3-6 composite is -34.16 dB at 2.4 mm, and the effective absorption bandwidth (EAB) reaches 4.8 GHz. Furthermore, the lowest emissivities of the HMCS@f-Fe2O3-6-20 wt %/polyetherimide (PEI) film in the 3-5 and 8-14 μm infrared wavebands are 0.212 and 0.508, respectively. These discoveries may pave the way for the development of radar-infrared compatible stealth materials from the perspective of microstructural design.

The effect of binders on the compressive mechanical behavior and impact resistance of graphene self-assembled ball

For a long time, graphene-based nanomaterials have broad application prospects because of their excellent multi-functional properties. Here, combined with coarse-grained molecular dynamics simulations, the compressive mechanical behavior and impact resistance of graphene-assembled hollow nanospheres (GAHNs) with interlayer binders have been explored systematically. It was found that, the introduction of binders between graphene nanosheets (GNs) can effectively improve the interfacial stress-transfer, by which the compression strength and modulus can be increased by ∼ 100% and ∼ 300%, respectively, with a low content of 4.23%. Meanwhile, it is found that the role of binders is changed under different impacting velocities. When the impact velocity is small, the strong connection between layers inhibits the impact force from decomposing to neighbor graphene nanosheets, while when the velocity is high, it will help maintain the structure from being torn. The tensile-shear tests reveal the contribution of binders to stress transfer theoretically. This work provides a theoretical insight for carbon hollow spheres into the mechanical response and impact resistance under different interface situation and lays the foundation for impacting resistance application.

Efficient Sodium Storage in Selenium Electrodes Achieved by Selenium Doping and Copper Current Collector Induced Displacement Redox Mechanisms

AbstractSelenium (Se), with its high specific volume capacity and high electronic and superior kinetics, is considered a promising electrode material with promising applications. However, the solvation and shuttle effects of polyselenides hinder their further application. The selenium/nitrogen‐doped hollow porous carbon spheres (Se/NHPCs) are obtained using the sacrificial template and in situ gas‐phase selenization methods. The Se species are doped into carbon matrixes in an adjustable amount to form Se‐C(N) bonds during this process. Density functional theory calculations show that the Se‐C(N) bond enhances the charge transfer between Na2Se and carbon matrix and binding energy, which improves rate performance and cycling stability. As expected, Se/NHPCs electrode exhibit high reversible capacity (480 mAh g–1 at 0.5 A g–1 after 200 cycles) and rate performance (311 mAh g–1 at 5 A g–1) as the anode for sodium‐ion batteries. A series of ex situ characterization results show that Cu2Se produced by copper current collector induction is effective in the adsorption of polyselenides while enhancing the electrode conductivity. Since the lattice structures of Cu2Se and Na2Se are similar, this displacement reaction that does not involve lattice reconfiguration provides an effective strategy for the preparation of high‐performance and low‐cost electrode materials.

Boosting ultrafast and durable sodium storage of hard carbon electrode with graphite nanoribbons

Hard carbons are emerged as one of the most promising candidates for sodium storage, but suffer from poor rate performance and inferior cycling stability. Herein, we design novel hierarchically hollow hard carbon spheres by combining hydrothermal growth and catalytic graphitization. The carbon spheres have a unique tremella-like morphology assembled from ultrathin heterostructured nanosheets with interwoven graphitic ribbons/amorphous carbon textures. When employed as anode in sodium-ion batteries, the 3D hierarchical structure is able to minimize the reaction length and accelerate the ion transfer; meanwhile, the graphite nanoribbons can offer electron immigration pathways and serve as supporting framework to protect the electrode off crack. As such, the carbon electrode delivers a high capacity of 278 mAh g−1 at 0.1 A g−1, and presents no dramatic capacity loss during a long-term charge/discharge test for 1000 cycles. More importantly, the hard carbon electrode has unexpectedly ultrafast sodium storage capability. Even under a very high current density of 10 A g−1, it retains a large capacity of 146 mAh g−1, giving a retention rate of 68% against the capacity at 0.05 A g−1, which is rarely achieved for state-of-the-art hard carbon anodes.

Yolk-shell Co catalysts with controlled nanoparticle/single-atom ratio for aqueous levulinic acid hydrogenation to γ-valerolactone

Precise and facile tailoring of metal nanoparticle/single-atom ratio to optimize the catalytic hydrogenation activity and durability is important yet challenging, owing to the lack of efficient synthetic methodology. Herein, we report a brand-new Co catalyst with precisely tailored Co NP/Co SA ratio encapsulated into a hollow carbon sphere, skillfully fabricated by stepwise coating of bimetallic Zn/Co zeolitic imidazole frameworks with silica and 8-quinolinol modified chitosan before pyrolysis and acid washing. The transformation of the target catalyst and the tailoring of Co NP/Co SA ratio are well investigated by various characterization techniques including TEM, aberration-corrected scanning TEM (AC-STEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS), etc. It is found that the yolk-shell structured Co catalyst integrated with nearly equivalent nanoparticles and sing-atoms are highly active and stable towards aqueous levulinic acid (LA) hydrogenation to γ-valerolactone (GVL). Combined with H2-TPD and LA adsorbed FT-IR investigations, it is revealed that the superior activity originates from the synergism of Co nanoparticles and single-atoms, since H2 dissociation and CO adsorption are facilitated by Co nanoparticles and single-atoms, respectively, leading to a lowered energy barrier during the hydrogenation reaction. This study will shed light on the precise tailoring of metal nanoparticle/single-atom ratio and also provides a new insight into the development of highly efficient non-noble metal catalysts for sustainable biomass conversion.

Nitrogen/Phosphorus/Boron-Codoped Hollow Carbon Spheres as Highly Efficient Electrocatalysts for Zn–Air Batteries

Nitrogen/Phosphorus/Boron-Codoped Hollow Carbon Spheres as Highly Efficient Electrocatalysts for Zn–Air Batteries

N-doped hollow carbon spheres as a high-performance anode for potassium-based dual-ion battery

Potassium-based dual-ion batteries (KDIBs) have become an alternative product for lithium-ion batteries owing to their high voltage, environmental friendliness and low cost. In this paper, nitrogen-doped activated hollow carbon nanospheres (N-AHCSs) with high specific surface area, porous structures and large interlayer spacing were prepared as anodes for KDIBs. The N-AHCSs are characterized by large interlayer spacing, hollow spheres structures and doping nitrogen. The large interlayer spacing and hollow structures are conducive to intercalation/deintercalation and diffusion behaviors of K ion. And nitrogen doping in carbon structures can provide sufficient K ion active sites. Therefore, the KDIBs composed of expanded graphite cathode and N-AHCSs anode deliver impressive specific capacity of 89.8 mAh g−1 at 0.1 A g−1 and super rate performance of 72.4 mAh g−1 at 1 A g−1 after ultra-long 2000 cycles. The results indicate that the N-AHCSs might be an excellent candidate for KDIBs anodes.

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.

Ultrafine Fe2C nanocrystals encapsulated in interconnected hollow carbon spheres as ORR electrocatalysts for Alkaline/Neutral Zn − Air batteries

The development of high − performance non − noble metal electrocatalysts for oxygen reduction reaction (ORR) superior to commercial Pt/C in both alkaline and neutral medium is critical for renewable energy technology such as metal − air battery, but remains a great challenge. Herein, hollow spherical framework structure is introduced during the solid − state reaction, enabling the active sites to exist with smaller size and more uniform dispersion. Specifically, a grape − cluster − like ORR catalyst (Fc@Fe − NHCS) is synthesized in which Fe2C nanocrystals and Fe − Nx sites are embedded in carbon layers supported by nitrogen − doped hollow carbon spheres. The resultant Fc@Fe − NHCS exhibits an ORR half − wave potential of 0.85 V in alkaline medium compared to 0.86 V for Pt/C. For neutral ORR, the half − wave potential of Fc@Fe − NHCS is 0.76 V, which is equal to that of Pt/C. Furthermore, Fc@Fe − NHCS demonstrates satisfactory peak power density and open − circuit voltage comparable to Pt/C when utilized as air cathode in self − prepared alkaline and neutral zinc − air batteries (ZABs). The co − action of the spherical framework structure with active sites of Fe2C nanocrystals and Fe − Nx sites ensures excellent ORR electrocatalytic performance, which provides a favorable electrocatalyst for various energy devices including alkaline and neutral ZABs.

A Rechargeable K/Br Battery

AbstractThe current limited and uneven distribution of lithium resources has stimulated strong motivation to develop new rechargeable batteries that use alternative charge carriers. Potassium‐based batteries are promising candidates for future large‐scale energy storage due to their low cost and high operating voltage. Here for the first time, a rechargeable K/Br battery is reported, which is assembled with a hollow carbon spheres cathode, a K metal anode, and a SOBr2 electrolyte containing AlBr3 and potassium bis‐(fluorosulfonyl)imide. The in situ formed crystalline KBr protective film during discharging plays a significant role in this system. The redox reaction between the KBr film and liquid Br2 at the cathode contributes to the main reversible capacity. K/Br battery exhibits high capacity (up to 400 mAh g‐1) and constant operating voltage (at 3.72 V vs K+/K). As a proof of concept, the K/Br battery demonstrated in this work points to a new pathway for low‐cost and next‐generation rechargeable batteries.

Hollow mesoporous carbon nanospheres space-confining ultrathin nanosheets superstructures for efficient capacitive deionization

In this work, we propose a novel strategy to fabricate nickel silicate nanoflakes inside hollow mesoporous carbon spheres (Ni3Si2O5(OH)4/C). Hollow mesoporous carbon spheres (HMCSs) can well regulate and limit the growth of Ni3Si2O5(OH)4 nanosheets, which obviously enhance the structural stability and conductivity of the composites. The core-shell Ni3Si2O5(OH)4/C superstructure has been proven to possess an extremely excellent electrosorption capacity of 28.7 mg g−1 at 1.2 V under a NaCl concentration of 584 mg L−1 for capacitive deionization (CDI). This outstanding property can be attributed to the core-shell superstructure with ultrathin Ni3Si2O5(OH)4 nanosheets as the stable core and mesoporous carbon as the conductive shell. This work will provide a direction for the application of core-shell superstructure carbon-based nanomaterials as high-performance electrode materials for CDI.