Hollow Carbon Shells Research Articles

Co/FeC core–nitrogen doped hollow carbon shell structure with tunable shell-thickness for oxygen evolution reaction

Herein, multi-core-shell structure Co/FeC@N-doped hollow carbon (Co/FeC@NHC) with tunable carbon shell thickness is well crafted by a novel and simple strategy. Novel core-shell structure consisting of polydopamine (PDA) shell with different thickness and bimetal-based metal–organic frameworks (MOFs) Co/Fe core with cubic morphology are first prepared, followed by a thermal and etching treatments to fabricate hollow composite materials composed of multiple Co/FeC cores evenly distributed in N-doped carbon shell. PDA acts as a carbon and nitrogen source simultaneously to form N-doped hollow carbon in this procedure. Creatively, the N-doped hollow carbon shell protects Co/FeC core and against the degradation, in addition to enhance the conductivity of Co/FeC@NHC. Through adjusting the PDA shell thickness simply, Co/FeC@NHC with tunable N-doped carbon shell thickness is well crafted. The Co/FeC@NHC-1 with the best electrocatalytic performance is obtained by optimizing the thickness of N-doped hollow carbon shell. The Co/FeC@NHC-1 exhibits the highest activity for the oxygen evolution reaction (OER) and outstanding stability and durability. Hence, this research may establish a promising path for the rational design of metals@carbon composite with controllable structure which can act as highly efficient electrocatalysts for (OER).

Hollow N-doped carbon polyhedra embedded Co and Mo2C nanoparticles for high-efficiency and wideband microwave absorption

Carbon materials with multi-components and hollow structures can be used as promising candidates in microwave absorption materials, however, rational design and construction of the special structures is still hard to achieve. In this work, a hollow structural bimetallic carbon polyhedron (CoMo@HNCP) is synthesized by the pyrolysis of core-shell ZIF-8@HZIF-CoMo polyhedrons. Owing to the uniform distribution of Mo2C and metallic Co nanoparticles in the hollow N-doped carbon shell, the generated multi-heterogeneous interfaces are in favor of dipolar and interfacial polarization, resulting in enhanced conduction loss, matched impedance as well as multiple scatterings. Typically, with a filler loading of 30 wt%, the minimum RL of CoMo@HNCP reaches −44.8 dB and the effective absorption bandwidth is as wide as 6.56 GHz with the absorber thickness of 2.5 mm, which is better than that of ZIF-8 derived N-doped carbon polyhedron and HZIF-CoMo derived bimetallic carbon polyhedron. The usage of bimetallic HZIF to assemble core-shell nanomaterials is proven to be an novel and excellent way to assembly microwave absorbers with multi-heterogeneous interfaces and hollow structures.

Embedding Co2P nanoparticles into co-doped carbon hollow polyhedron as a bifunctional electrocatalyst for efficient overall water splitting

The reasonable design and construction of non-precious metal electrocatalysts with low cost and high performance is critical for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, a facile polymerization-pyrolysis method is proposed to encapsulate Co2P nanoparticles in co-doped hollow carbon shell by using ZIF-67 and P-containing polymers as precursor. The unique construction not only effectively prevents nanoparticles from detaching, showing good stability after long-term testing, but also provides abundant active sites, large surface areas and large pore volumes, enabling the electrolyte and electrode material to full contact. As expected, the Co2P/NPSC-800 performs superior HER performance with low overpotential of 173 mV at 10 mA cm−2 and excellent stability of 88% retention for 35 h and OER performance with low overpotential of 320 mV at 10 mA cm−2, which endows Co2P/NPSC-800 with good catalytic activity in overall water splitting. Furthermore, density functional theory (DFT) calculations reveal that the metallic property and the decreased reaction barriers of Co2P can promote the catalytic reactions. This work offers an effective route in synthesizing other transition metal phosphides with high catalytic properties.

One-pot sol-gel synthesis of Si/C yolk-shell anodes for high performance lithium-ion batteries

Silicon (Si) materials are promising anodes for lithium-ion batteries (LIBs) due to their high theoretical capacity and low discharge potential. Nevertheless, their actual use is seriously restricted by their low conductivity and huge volumetric change. Developing a Si/C composite with a yolk-shell structure is an effective method to overcome the issues including the low electrical conductivity and poor cycling stability caused by Si. In this work, a facile one-pot sol-gel approach is developed to synthesize a Si/C yolk-shell composite in the presence of cost-effective resorcinol-formaldehyde (RF) and tetraethyl orthosilicate (TEOS) as precursors. In this structure, Si nanoparticles (NPs, ∼80–100 nm) are well encapsulated in a ∼12 nm thick hollow carbon shell (HC). There is a 60 nm-thick void space between the silicon core and outer carbon layer. The as-prepared Si@HC sample showed a high charge capacity of 1807.4 mA h g −1 and retained 999.5 mA h g −1 at 100 mA g −1 beyond 100 cycles. Furthermore, this material exhibited a reversible capacity of 500 mA h g −1 after 2000 cycles at 1 A g −1 . • The Si@SiO 2 @RF core-shell precursor can be synthesized by a one-step sol-gel approach. • The size of the thickness of the carbon shell can be adjusted conveniently. • Si@HC anodes exhibit high reversible capacities as well as excellent cycle stability.

Nanosized FeS2 Particles Caged in the Hollow Carbon Shell as a Robust Polysulfide Adsorbent and Redox Mediator

As one of the most promising candidates for next-generation energy storage technology, lithium–sulfur (Li–S) battery has been attracting increasing attention due to its high theoretical specific ca...

Template-free synthesis and lithium-ion storage performance of multiple ZnO nanoparticles encapsulated in hollow amorphous carbon shells.

Due to the limited utilization of electrode materials, the rational design and facile synthesis of composite structures are still challenging issues for lithium-ion batteries (LIBs). Herein, a simple approach has been developed to prepare multiple core–shell structures of ZnO nanoparticles (NPs) encapsulated in hollow amorphous carbon (AC) shells. The as-synthesized ZnO@AC composites showed a uniform dispersion of ZnO NPs, compliant buffer AC shells, and nanoscale void spaces between the ZnO NP cores and AC shells. As a result of their structural merits, the ZnO@AC composites were evaluated as anode materials for LIBs and delivered enhanced coulombic efficiency, high reversible capacity, high rate capability, and improved cycling stability.

Uniform yolk-shell structured Si-C nanoparticles as a high performance anode material for the Li-ion battery.

Silicon (Si) is a promising candidate as an anode material for lithium-ion batteries. However, its application is hindered by poor cycling stability and rate-capability due to structural degradation, resulting from large volume changes during cyclic charging and discharging. In this paper, we report that uniform-sized Si@void@C nanoparticles can be prepared by magnesiothermic reduction of SiO2@void@C. Si nanoparticles are in hollow carbon shells with a large void space between the carbon shell and particles. Thus, each Si particle can expand freely within the well-designed void space without destroying the outer carbon shell, and benefit the solid-electrolyte interphase film stabilization on the carbon shell. The new material shows a high capacity of 1598 mA h g-1 at a current density of 1 A g-1, a long cycle life of 1500 cycles with 85% capacity retention, and a high Coulombic efficiency of 99.6% as well, and might be a promising Si-based anode material for Li-ion battery applications.

Structure-induced hollow Co3O4 nanoparticles with rich oxygen vacancies for efficient CO oxidation

Co3O4 has been considered as one kind of promising catalysts for the oxidation of CO. According to the Mars-van Krevelen mechanism, oxygen vacancies of Co3O4 play a significant role in catalytic activity. Herein, we report a novel structure-induced strategy to develop hollow Co3O4 with rich oxygen vacancies for efficient oxidation of CO. Through a reduction-oxidation pyrolysis process, the metal-organic frameworks (MOFs) precursor (i.e., ZIF-67) is transformed into H-Co3O4@H-C, in which hollow Co3O4 (H-Co3O4) nanoparticles (NPs) are embedded in hollow carbon (H-C) shell. The hollow Co3O4 NPs feature rich oxygen vacancies and finish a complete conversion of CO at 130°C, which is much lower than that of solid Co3O4 (the temperature of full CO conversion T 100= 220°C). Besides, the hollow carbon shell could also reduce the diffusion resistance during the oxidation process. Benefiting from the unique hollow structures, H-Co3O4@H-C even shows comparable activity to noble metal catalysts under high weight hourly space velocities (WHSVs) up to 240,000 mL h–1 gcat.–1. Furthermore, the H-Co3O4@H-C catalyst also shows good durability with only a slight decline after the reaction has been operated for 24 h.

Facile synthesis of yolk-shell structured Fe3O4@C-Au nanoparticles for thermotherapic application

Abstract Yolk-shell nanostructures haves promising applications in cancer therapy due to their great potential for multi-functions. However, the control over its structure and morphology still remains a big challenge. Herein, yolk-shell Fe3O4@C-Au composite nanostructure has been successfully synthesized with magnetic Fe3O4 nanoparticles encapsulated in hollow carbon shells and Au nanoparticles well dispersed. The yolk-shell structure has a uniform size of ~80 nm and a high surface area of 325.13 m2/g. The Fe3O4 and Au nanoparticles are 10 and 3 nm, respectively. The as-prepared Fe3O4@C-Au showed good biocompatibility during endocytosis process. The Fe3O4@C-Au suspension (150 μg/ml) shows efficient photothermal conversion effect and effectively damage 4T1 cells. The composite nanostructure Fe3O4@C-Au show promising applications in cancer diagnosis and therapy.

Self-assembled N-doped carbon with a tube-in-tube nanostructure for lithium-sulfur batteries

Lithium-sulfur batteries hold broad prospects as the low-cost and high-energy storage system. However, the practical application is limited by the intrinsic insulating nature of sulfur and severe shuttle effect of soluble polysulfide intermediates. Herein, we demonstrate a convenient self-assembly strategy for encapsulating carbon nanotubes in nitrogen-doped hollow carbon shells, to construct a nitrogen-doped tube-in-tube carbon nanostructure (NTTC) as a host material of sulfur. In this peculiar structure, the highly conductive carbon nanotube cores facilitate the electron transfer while the hollow porous structure is capable of accommodating high sulfur content of 70 wt% in the composites. Moreover, the nitrogen doping helps to alleviate the shuttle effect owing to enhanced chemisorption towards polysulfides. Benefiting from these merits, the NTTC/S composite with the high areal mass loading of ~2.5 mg cm−2 presents a high reversible capacity (1346.9 mAh g−1 at 0.05 C) and excellent rate capability (533.5 mAh g−1 at 3C). More impressively, NTTC/S electrode exhibits good cycling stability at a high rate of 2 C corresponding to slight capacity decay of 0.055% per cycle over 500 discharge/charge cycles.

Highly Isolated Cobalt Sulfide Nanoparticles Encapsulated in 3D Hollow Nitrogen Doped Carbon Sheells for Superior Lithium and Sodium Storage

Highly Isolated Cobalt Sulfide Nanoparticles Encapsulated in 3D Hollow Nitrogen Doped Carbon Sheells for Superior Lithium and Sodium StorageWei Huang, a, b Huihui Shangguan, b Christian Engelbrekt, a Xiaowen Zheng, b Fei Shen, a Xinxin Xiao, a Lijie Ci, b Pengchao Si b, * and Jingdong Zhang a, * a Department of Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark. b SDU & Rice Joint Center for Carbon Nanomaterials, Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, School of Materials Science and Engineering, Shandong University, Jinan 250061, P. R. China.Hollow materials derived from metal-organic frameworks (MOFs) present a class of promising electrode materials for energy storage technology. Herein, we report the design and nanoengineering of highly isolated cobalt sulfide nanoparticles embedded in hollow nitrogen-doped carbon shells (Co9S8/HNCS) for superior lithium and sodium storage. Initially, hollow intermediates with preserved cobalt component were prepared by simultaneously dissociating cobalt containing zeolitic-imidazolate-frameworks-67 (ZIF-67), and polymerizing dopamine in a Tris-HCl solution (pH = 8.5). The poly-dopamine (PDA) wrapped intermediates inherited the polyhedron structure of the ZIF-67 crystals. The final Co9S8/HNCS composite was obtained via a combined carbonization and sulfurization treatment of the intermediates, allowing the formation of hollow polyhedrons of nitrogen-doped carbon layers (900 ± 100 nm) derived from PDA and the encapsulation of highly monodispersed cobalt sulfide nanoparticles (11 ± 2 nm). This configuration not only shortened the ionic diffusion distance, and accommodated volume expansion during lithium or sodium ion insertion/extraction, but also promoted the overall electronic conductivity, and provided more active sites during cycling. As a result, Co9S8/HNCS composite exhibited an impressive reversible capacity of 755 mA h g-1 at 500 mA g-1 after 200 cycles for lithium ion storage, and capacities of 327 mA h g-1 at 500 mA g-1 after 200 cycles and 224 mA h g-1 at 1000 mA g-1 after 300 cycles for sodium ion storage. Essential factors associated with the structural stability and changes during cycling have been identified and the discharge/charge mechanism has been discussed. Figure 1

Theoretical Computational Fluid Dynamics Study of the Chemical Vapor Deposition Process for the Manufacturing of a Highly Porous 3D Carbon Foam

AbstractAerographite is a three‐dimensional carbon foam with a tetrapodal morphology. The manufacturing of aerographite is carried out in a chemical vapor deposition (CVD) process, based on a zinc oxide (ZnO) template, in which the morphology is replicated into a hollow carbon shell. During the replication process, the template is reduced by the simultaneous formation of the carbon structure. The CVD process is one of the most efficient methods for the manufacturing of various carbon nanostructures, such as graphene or carbon nanotubes (CNTs). Based on the growth mechanism of aerographite, a computational fluid dynamics model is presented for the fundamental investigations of the temperature and flow/microflow behavior during the replication process. This allows a deeper process understanding and further optimizations.

Well-defined cobalt sulfide nanoparticles locked in 3D hollow nitrogen-doped carbon shells for superior lithium and sodium storage

Hollow nanostructured materials present a class of promising electrode materials for energy storage and conversion. Herein, 3D hollow nitrogen-doped carbon shells decorated with well-defined cobalt sulfide nanoparticles (Co9S8/HNCS) have been constructed for superior lithium and sodium storage. Two steps are involved in the designed preparation procedure. First, hollow intermediates with preserved cobalt components are controllably fabricated by simultaneously dissociating cobalt containing zeolitic-imidazolate-frameworks-67 (ZIF-67), and polymerizing dopamine in a Tris–HCl solution (pH = 8.5). The polydopamine (PDA) wrapped intermediates inherits the polyhedral structure of the ZIF-67 crystals. In the second step, the final Co9S8/HNCS composite is obtained via a combined carbonization and sulfurization treatment of the intermediates, allowing the formation of hollow polyhedrons of nitrogen-doped carbon shells (900±100 nm) derived from PDA and the encapsulation of highly uniform cobalt sulfide nanoparticles (11±2 nm). This configuration is believed to not only shorten the lithium or sodium ion diffusion distance and accommodate volume change during lithium or sodium ion insertion/extraction, but also to enhance the overall electrical conductivity and the number of active sites. As a result, the Co9S8/HNCS composite exhibits an impressive reversible capacity of 755 mA h g-1 at 500 mA g-1 after 200 cycles for lithium ion storage, and capacities of 327 mA h g-1 at 500 mA g-1 after 200 cycles and 224 mA h g-1 at 1000 mA g-1 after 300 cycles for sodium ion storage. Essential factors especially the structural stability during cycling have been identified, and the discharge/charge mechanism is discussed.

Hollow carbon shells enhanced by confined ruthenium as cost-efficient and superior catalysts for the alkaline hydrogen evolution reaction

Ru species encapsulated in HCSs can effectively break the homogeneous electron distribution and generate abundant active sites for the HER.

Millerite Core-Nitrogen-Doped Carbon Hollow Shell Structure for Electrochemical Energy Storage.

Nickel sulfides have drawn much attention with the benefits of a high redox activity, high electrical conductivity, low cost, and fabrication ease; however, these metal sulfides are susceptible to mechanical degradation regarding their cycling performance. Conversely, hollow carbon shells exhibit a substantial electrochemical steadiness in energy storage applications. Here, the design and development of a novel millerite core-nitrogen-doped carbon hollow shell (NiS-NC HS) structure for electrochemical energy storage is presented. The nitrogen-doped carbon hollow shell (NC HS) protects against the degradation and the millerite-core aggregation, giving rise to an excellent rate capability and stability during the electrochemical charging-discharging processes, in addition to improving the NiS-NC HS conductivity. The NiS-NC HS/18h supercapacitor electrode displays an outstanding specific capacitance of 1170.72 F g-1 (at 0.5 A g-1 ) and maintains 90.71% (at 6 A g-1 ) of its initial capacitance after 4000 charge-discharge cycles, owing to the unique core-shell structure. An asymmetric-supercapacitor device using NiS-NC HS and activated-carbon electrodes exhibits a high power and energy density with a remarkable cycling stability, maintaining 89.2% of its initial capacitance after 5000 cycles.

Controlled scalable synthesis of yolk-shell structured large-size industrial silicon with interconnected carbon network for lithium storage

Yolk-shell structured nano-Si@void@C can greatly improve the electrical conductivity and buffer the large volume change of silicon nanoparticles, whereas inter poor electrical connection between Si cores and carbon shells still limits the lithium storage performance. Besides, it usually requires complex synthesis conditions and expensive nano-level silicon sources. Herein, we succeed in making the large-size industrial silicon (ca. 400–500 nm) to a yolk-shell structure with a controllable space buffer layer. Most importantly, an interconnected porous carbon network deriving from the thermal decomposition of carbon chains in silicon sources is formed within the carbon shell simultaneously, which can improve the electrical contact between Si cores and hollow carbon shells and prevent the active particles exposure to the electrolyte. With the help of static outer thin carbon shell, optimized inner void and the flexible electrically conductive carbon network, such yolk-shell structured Si@void@C submicron particles synthesizing by one-step carbon-coating procedure exhibit high initial coulomb efficiency of 62%, good rate performance, and excellent long cycling stability with 950.7 mAh g−1 at 100 mA g−1 after 100 cycles. The low consumption and stable synthesis method make it feasible for large-scale fabrication of the yolk-shell structured Si/C composites as commercial anodes for energy storage.

In-situ activation for optimizing meso-/microporous structure of hollow carbon shells for supercapacitors

In-situ activation for optimizing hierarchically meso-/microporous structure of hollow carbon shells which were produced using a simple calcination process with NaOH was demonstrated to effectively enhance the performance in supercapacitors. The electrical conductivity, pore structure and surface area of the material were tuned by adjusting the amount of NaOH. The optimized sample showed a specific capacitance of 374.3[Formula: see text]F g[Formula: see text] at a current density of 0.2[Formula: see text]A g[Formula: see text] and 191.0[Formula: see text]F g[Formula: see text] at 10[Formula: see text]A g[Formula: see text], with almost no degradation after 10,000 cycles.

Nitrogen, phosphorus, and sulfur tri-doped hollow carbon shells derived from ZIF-67@poly (cyclotriphosphazene-co-4, 4′-sulfonyldiphenol) as a robust catalyst of peroxymonosulfate activation for degradation of bisphenol A

Heteroatom-doped carbon materials have emerged as attractive catalysts for peroxymonosulfate (PMS) activation and environment remediation recently due to its low cost and non-toxicity. In this study, novel N, P, and S tri-doped hollow carbon shells (NPSC) are elaborately fabricated using ZIF-67 and poly (cyclotriphosphazene–co-4,4′- sulfonyldiphenol) (PZS) as precursors. NPSC obtained at 700 °C shows better performance than those at other temperature (600 and 800 °C), and it can effectively degrade 90.1% of Bisphenol A (BPA) in the presence of PMS, which totally exceeds the performance of several common catalysts. It is found that for used catalyst, surface oxidation of carbon networks and blockage of heteroatom-doping active sites are two main reasons for the deterioration of reusability. Electron paramagnetic resonance (EPR) measurements and radical quenching tests are conducted to reveal that hydroxyl, sulfate, and superoxide radicals are main reactive species for BPA degradation in NPSC/PMS systems. Finally, it is proposed that synergistic effects of N, P, and S doping may greatly break the electroneutrality of pristine carbon structures, promote the O-O breakage of PMS, and facilitate the generation of radicals. Such findings dedicate to enlighten new thoughts and deeper understanding for synthesis of heteroatom-doped porous carbon in PMS activation.

Au nanoparticle@hollow mesoporous carbon with FeCo/graphitic shell nanoparticls as a magnetically recyclable yolk\u2013shell nanocatalyst for catalytic reduction of nitroaromatics

We have developed a highly stable and magnetically recyclable yolk–shell nanocatalyst for catalytic reduction of nitroaromatics. This nanocatalyst is composed of a ~13 nm Au nanoparticle encapsulated in a hollow mesoporous carbon (hmC) shell with a diameter of ~120 nm and a thickness of ~15 nm. The hmC shell contains ~6 nm FeCo/graphitic carbon shell (FeCo/GC) nanoparticles. We have synthesized the Au@hmC-FeCo/GC nanocatalyst by thermal decomposition of Fe and Co precursors in silica of a solid core/mesoporous shell structure containing a Au nanoparticle within the core, subsequent ethylene chemical vapor deposition (CVD), and then removal of the silica by treatment with aqueous HF. The Au@hmC-FeCo/GC has superparamagnetism and high saturation magnetization (29.2 emu g−1) at room temperature. It also shows a type IV sorption isotherm, typical for mesoporous carbon (pore diameter = 3.5 nm), thereby ensuring ready accessibility to the Au core by substrates. We have shown that the Au@hmC-FeCo/GC catalyses the reduction of 4-nitrophenol and 4-nitrotoluene more efficiently than Au nanoparticles do, can be separated very quickly from the reaction mixture using an magnet, and can be reused for the same reduction reaction at least five times without loss of the initial level of catalytic activity.

Nano-sized ZIF-8 anchored polyelectrolyte-decorated silica for Nitrogen-Rich Hollow Carbon Shell Frameworks toward alkaline and neutral supercapacitors

Core-shell hybrid precursors (ZIF-8/PP-SiO2) engineered by zeoliticimidazolate framework (ZIF-8) depositing on the polyelectrolyte-decorated silica (PP-SiO2) are successfully transformed into unusual N-rich hollow carbon shell frameworks (NHCSFs) with adjustable physicochemical properties by the layer-by-layer assembly, interface engineering and subsequent carbonization, which is the first example that systematically elucidates the formation and structure-property correlation of unique three-dimensional (3D) carbon frameworks. The optimal NHCSF-3 displays superior performance with high capacitance approaching 253.6 F g−1 at 1 A g−1, excellent rate capability delivering 79% capacitance retention after a 50-fold increase of the rate, and long lifetime (92.1% retention for 20000 cycles). The studies on alkaline and neutral NHCSF-3//NHCSF-3 supercapacitors demonstrate that the latter with high voltage up to 1.6 V using a Na2SO4 electrolyte can deliver high energy density of 13.3 Wh kg−1. The distinctly enhanced performance illustrates that, except for the factors such as morphology, surface area, pore volume, and N-doping level, hierarchical porosity also significantly boosts electrochemical properties of the materials because of providing efficient charge/mass transport. Overall, this research provides an efficient platform for precisely modulating the structure of MOF-based carbons to develop multifunctional hollow architectures for satisfying enormous demands in upcoming energy devices.