Carbon Shell Research Articles

Enhanced Capacitive Deionization of Hollow Mesoporous Carbon Spheres/MOFs Derived Nanocomposites by Interface-Coating and Space-Encapsulating Design.

Exploring new carbon-based electrode materials is quite necessary for enhancing capacitive deionization (CDI). Here, hollow mesoporous carbon spheres (HMCSs)/metal-organic frameworks (MOFs) derived carbon materials (NC(M)/HMCSs and NC(M)@HMCSs) are successfully prepared by interface-coating and space-encapsulating design, respectively. The obtained NC(M)/HMCSs and NC(M)@HMCSs possess a hierarchical hollow nanoarchitecture with abundant nitrogen doping, high specific surface area, and abundant meso-/microporous pores. These merits are conducive to rapid ion diffusion and charge transfer during the adsorption process. Compared to NC(M)/HMCSs, NC(M)@HMCSs exhibit superior electrochemical performance due to their better utilization of the internal space of hollow carbon, forming an interconnected 3D framework. In addition, the introduction of Ni ions is more conducive to the synergistic effect between ZIF(M)-derived carbon and N-doped carbon shell compared with other ions (Mn, Co, Cu ions). The resultant Ni-1-800-based CDI device exhibits excellent salt adsorption capacity (SAC, 37.82mg g-1) and good recyclability. This will provide a new direction for the MOF nanoparticle-driven assembly strategy and the application of hierarchical hollow carbon nanoarchitecture to CDI.

Dual confinement of RuOx nanoparticle using polar MnNiO and armored carbon for boosting water electrolysis

The poor stability of nanoparticle catalysts with catalytic activity is a significant obstacle to their industrial application. The establishment of rational nanoparticle structures to elucidate the relationship between catalyst structure and its catalytic activity and stability is crucial for constructing nanoparticle catalysts that are both highly active and stable. We propose a strategy to construct a dual-confinement effect of the nanoparticle, specifically by regulating the polarization of the MnNiO support to enhance strong oxide-support interactions (SOSI) and encapsulating the outer layer of nanoparticles with a carbon shell, which has been proven effective in improving the activity and stability of nanoparticle-based oxygen evolution reaction (OER) electrocatalysts. At a current density of 100 mA cm−2, the armor C@RuOx@MnNiO catalyst displays an overpotential of 260 mV for the OER. After the OER test for 100 h, the current density of C@RuOx@MnNiO shows no significant decay, whereas that of RuOx@MnNiO and RuOx@MnO rapidly decreases, indicating significant catalytic activity and stability of the catalyst. The assembled C@RuOx@MnNiO||Pt/C electrode demonstrates excellent alkaline water electrolysis performance in an MEA electrolyzer, requiring only a low cell voltage of 1.76 V to achieve an ampere-level current density of 1 A cm−2. In-situ electrochemical Raman spectroscopy reveals the significant interaction between nanoparticles and the polar support. The reduction in Gibbs free energy, which establishes the rate-determining step (RDS) of OER, is caused by the charge redistribution caused by polar Mn doping in RuOx@MnNiO and the coordination structure modifications, as shown by density functional theory calculations. This work provides an approach to designing efficient and stable nanoparticle electrocatalysts through the dual-confinement effect of SOSI-induced strong interactions and armor carbon layers.

Facile and precise synthesis of core-shell ZnO/C nanorods with excellent microwave absorption

Carbonaceous materials have great prospects in microwave absorption due to their lightweight and corrosion resistance. However, their high conductivity leads to poor impedance matching, posing a significant challenge for obtaining outstanding microwave absorption (MA) materials from carbonaceous materials. In this work, the core-shell ZnO/C nanorods (ZCNs) are prepared by covering conductive carbon on the surface of ZnO nanorods through a simple stirring process in ambient temperature and calcination treatment. The thickness of carbon shell is carefully regulated to realize appropriate impedance matching and strong microwave dissipation capability. ZCN with 30.2 nm of carbon shell achieves outstanding microwave absorption in low frequency and broadband microwave absorption because of the synergies of optimized impedance matching and enhanced dielectric loss: the reflection loss of 49.9 dB at 6.32 GHz, and the effective absorption bandwidth of 6.4 GHz at a corresponding thickness of 2.0 mm. RCS simulation results have verified its excellent performance in practical application. This study proposes a simple and effective idea for the efficient utilization of carbonaceous materials in microwave absorption.

Three-dimensional MoS2 nanosheets embeded within NiTe nanorods forming semicoherent heterojunctions achieving high-performance potassium-ion batteries

Three-dimensional MoS2 nanosheets uniformly embedded within NiTe nanorods are synthesized via one-step hydrothermal method and subsequently coated with a carbon layer to form stable NiTe@MoS2@C heterojunctions. The heterojunctions exhibit moderate lattice mismatch (δ =20.0 %), strong electric fields, and uniform carbon shells, resulting in unique electronic configurations and abundant active sites. As an anode for potassium-ion batteries, NiTe@MoS2@C demonstrated an high reversible capacity of 258.4 mAh g−1 after 100 cycles at a rate of 200 mA g−1. Moreover, it showed a stable reversible capacity of 177.5 mAh g−1 at a high rate of 5000 mA g−1, indicating excellent rate performance. Notably, even in the NiTe@MoS2@C//perylene tetracarboxylic dianhydride full battery configuration, a significant reversible capacity of 87.4 mAh g−1 was maintained after 100 cycles at a rate of 200 mA g−1, manifesting its remarkable potential for practical applications in potassium-ion batteries. Theoretical calculations further revealed that the well-designed NiTe@MoS2 heterojunction significantly enhances K+ ion diffusion.

Influence of Carbonization Conditions and Temperature Variations on the Characteristics of Coconut Shell Carbon

Influence of Carbonization Conditions and Temperature Variations on the Characteristics of Coconut Shell Carbon

Enhanced oxygen evolution reaction using carbon-encapsulated Co-Fe-Al Alloy

Transition metal-based alloy nanostructures have emerged as promising catalysts for electrochemical water splitting, offering a potential solution to the growing demand for clean and renewable energy. Also, research on encapsulation engineering of alloy nanostructures using carbon matrices has recently advanced, presenting a new approach that combines the conductive properties of carbon matrices with an alloy structure to enhance electrochemical performance in water splitting. However, the specific roles of the alloy core, carbon shell, and their synergistic effect in improving electrochemical performance are still not well understood. In this paper, we report on the encapsulation of a ternary Co–Fe–Al alloy nanostructure using a carbon matrix and investigate its electrochemical oxygen evolution reaction (OER). The optimized carbon matrix-encapsulated Co0.3Fe0.2Al0.5 alloy catalyst demonstrated superior electrocatalytic activity for OER (achieving 250 mV at 10 mA cm−2) and long-term stability. Through density functional theory calculations, we also elucidate the crucial role of Al in enhancing the OER catalytic performance of the proposed carbon-encapsulated Co–Fe alloy catalyst. By comparing the free electron concentration and required applied potentials to trigger OER, we provide insights into the beneficial effects of incorporating Al into the Co–Fe alloy catalyst.

Alleviated volume changes of germanium anode via facile chemical confinement strategy

Germanium (Ge) anode shows great promise in overcoming unsatisfied capacity and dendrite formation concerns facing conventional graphite anodes in next generation lithium ion batteries. However, volume changes during repeated alloying and de-alloying cycles seriously impair structural stability and cycle lifespan. In this work, a facile chemical confinement strategy has been firstly proposed to alleviate volume changes of Ge anode. Benefited from strong binding interaction between Ge and ZnS, discrete Ge nanoparticle can be successfully encapsulated within thin protective ZnS shell and N-doped carbon layer (Ge-ZnS@N-C) after two-step carbonization and sulfurization of polydopamine-coating Zn2GeO4 nanorod precursors. In contrast, bulk Ge aggregates and hollow N-doped carbon nanotubes can be formed without chemical confinement of ZnS. The as-prepared Ge-ZnS@N-C sample displays multifold structural merits, including nanosized Ge particles with highly electrochemical activity, sufficient pores and functional groups that facilitate ion diffusion. Besides, protective ZnS shell and N-doped carbon layer can suppress volume changes of Ge nanoparticles and guarantee high electrode reversibility, demonstrated by a series of in-situ and ex-situ experiments. The as-synthesized Ge-ZnS@N-C anodes exhibit stable long-cycle performance (1389.7 mAh/g after 450 cycles at a current density of 0.5 A/g) and excellent rate performance (548.5 and 397.8 mAh/g at 5.0 and 8.0 A/g, respectively).

Facile synthesis of nano-si/graphite-carbon anode through microwave-induced carbothermal shock for lithium-ion batteries

We present a cost-effective synthesis process for producing a carbon-coated nano-Si@Graphite (n-Si@G-C) anode, in which nano-sized Si (n-Si) particles (∼50 nm in size) are anchored onto natural graphite particles by a carbothermal shock through microwave induction. During the carbothermal shock process, graphite undergoes a fast increase in temperature resulting in micron-sized Si (m-Si) particles (∼4 μm in size) to undergo stress fractures due to rapid thermal expansion. This process leads to the formation of abundant n-Si particles onto graphite particles. Subsequently, a thin carbon shell is introduced by a wet-coating process combined with a thermal decomposition of coal-tar pitch. The amorphous carbon shell offers multiple functionalities: i) preventing direct exposure of n-Si particles to the electrolyte, ii) accommodating their volume expansion, and iii) maintaining electron conduction pathways. The resulting n-Si@G-C anode allows a high reversible capacity (500.8 mAh g−1) as well as fast-charging characteristics. When utilized in a full-cell configured with a commercial-grade LiNi0.8Co0.1Mn0.1O2 cathode, it achieves a notable reduction in charging time (approximately 10.1 min@80 % state of charge). After 300 cycles, a high capacity retention (71.3 %) can be retained under 3C charging. Moreover, the distinctive structural features of the n-Si@G-C anode effectively suppress undesirable Li plating.

Controlled N-doped Fe3O4@C arrays: Achieving enhanced donor density and capacity for hybrid supercapacitors

Carbon modified nitrogen-doped Fe3O4(N–Fe3O4@C) nanorod array directly grown on carbon cloth was fabricated. Nitrogen-doping and carbon shell effectively decrease the potential barrier of ion migration of the oxides and improve the electrochemical performance. An enhanced donor density of N-Fe2O3 (7.6 × 1015 cm−3) is achieved with optimized doping temperature. Following with carbon coated, the optimized N–Fe3O4@C electrode showed ultrahigh capacitance over an extended potential window and remarkable cycling performance. A new quasi-solid-state supercapacitor with N–Fe3O4@C and NiCoP@Ni(OH)2 achieved high voltage to 2.0 V and high energy density (72.37 Wh kg−1, 2.36 mWh cm−3).

Effect of Crystal Structure on Dealloying Behavior in PtCo Alloy and Its Impact on the Oxygen Reduction Reaction

The proton exchange membrane fuel cell (PEMFC) is considered ideal for power generation due to its high energy conversion efficiency, low operating temperature, and environmentally friendly features. However, the performance of PEMFC is limited by the slow oxygen reduction reaction (ORR) at the cathode, necessitating the use of catalysts such as Pt to enhance the reaction. The Pt catalyst, although effective, poses the challenge of high cost. Consequently, numerous studies have been undertaken to develop more cost-effective catalysts that can match the excellent activity of platinum while maintaining high stability. In particular, the development of alloy nano-catalysts has garnered attention, and promising results have been reported for enhancing catalyst performance through dealloying on the surface of the alloy catalyst. Alloy catalysts prepared by the dealloying method offer the advantage of improving performance by selectively dissolving less-noble metal surfaces and constructing a Pt-rich shell layer. In this study, we synthesized two PtCo alloy catalysts with distinct crystal structures: face-centered cubic (FCC) and face-centered tetragonal (FCT). To prevent particle growth during the transformation from FCC to FCT when subjected to high-temperature heat treatment for an extended duration, we employed the carbon shell encapsulation technique. Subsequently, the synthesized catalyst underwent acid treatment for dealloying. We investigated the variations in dealloying characteristics based on crystal structures and examined their impact on electrochemical performance. Various characterizations, including X-ray diffraction (XRD), High-Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (SEM), Thermo-Gravimetric Analysis (TGA), and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), were conducted to validate the structure of the synthesized PtCo alloy nano-catalyst. Half-cell and unit-cell experiments were carried out to verify electrochemical properties and performance, following the testing protocol suggested by the Department of Energy (DOE) in 2020. Finally, we explored the relationship between the dealloying feature of FCC and FCT and their impact on electrochemical activity and stability.

PtCo nanoalloy embedded nitrogen-doped carbon nanotube for rechargeable Zn-air batteries

The large-scale application of metal-air batteries strongly depends on the development of cost-effective, highly efficient, and durable bifunctional oxygen catalysts. In this work, a facile approach for preparing the monodisperse PtCo nanoalloy anchored the nitrogen-doped carbon nanotubes (PtCo/NCNT) for zinc-air batteries is reported. The nitrogen-doped carbon shell prevents PtCo nanoalloy from exfoliation, dissolution, and aggregation and enables the accessibility of electrolytes to the alloy surface and the electron transfer. Besides, the strong interaction between PtCo nanoalloy and nitrogen-doped carbon can efficiently modulate the electronic structure of the formed active sites. When used as a cathode catalyst, the constructed rechargeable zinc-air battery presents higher power density (268 mW cm−2), specific capacity (840 mAh g−1), and excellent stability. More importantly, the PtCo/NCNT catalyst allows the all-solid-state cell to exhibit remarkable flexibility and high round-trip efficiency at various bending states, demonstrating a potential possibility to replace the conventional Pt/C and RuO2 catalysts.

Precise Regulation of Reactive Oxygen Species in Tumor Microenvironment for Alleviating Inhibitory Immunogenic Cell Death.

High level of C (ROS) within the tumor microenvironment (TME) not only damage tumor cells but also diminish the efficacy of immunogenic cell death (ICD) and the activity of tumor-infiltrating T lymphocytes, thereby limiting the effectiveness of immunotherapy. Therefore, precise modulation of ROS level is crucial to effectively eliminate tumor cells and activate ICD-induced immunotherapy. Here, an intelligent yolk shell nanoplatform (SPCCM) that features calcium carbonate shells capable of decomposing under acidic TME conditions, thereby releasing the natural antioxidant proanthocyanidins (PAs) and the photosensitizer Ce6 is designed. PAs scavenge ROS within tumors, extending the survival time of T lymphocytes, while Ce6, as an ICD inducer, generates high ROS concentrations upon laser irradiation, thus reaching the toxic threshold within tumor cells and inducing apoptosis. The resulting apoptotic cells serve as tumor-associated antigens, promoting dendritic cells (DCs) maturation, and activating ICD. By effectively neutralizing ROS in the TME, PAs sustainably reduce ROS level, thereby enhancing DCs activation and restoring antitumor immune cell activity suppressed by ROS (resulting in an eightfold increase in DCs activation). This study demonstrates effective synergistic effects between photodynamic therapy and immunotherapy by precisely modulating ROS level.

A hollow Core-Shell Cu2S@C nanoboxes for High-Performance electrochemical sodium storage

Aiming at the poor intrinsic conductivity and huge volume expansion of transition metal sulfides, carbon-coated cuprous sulfide hollow nanoboxes (Cu2S@C) with core–shell structure were designed via co-precipitation, facial carbon coating and in-situ sulfurization methods, and exhibited significantly improved electrochemical properties applied as sodium ion battery anode. The uniformly coated carbon shell can enhance the electrolyte infiltration, promote charge transfer efficiency, accelerate electrochemical conversion redox kinetics. The conversion reaction reversibility of restricted Cu2S cores show a significant improvement benefitting from accelebrating ion diffusion and spatial limitation. During the sulfidation, robust chemically and electronically bonded connections such as C-S moieties formed between the two phases, creating interconnected channels that facilliate rapid charge transfer kinetics and optimize structural durability. Moreover, the hollow core–shell structure can provide a buffer space for tolerating volume expansion and preventing agglomeration arising from the repeating Na+ insertion/desertion process, which can availably enhance cyclic stability. Thanks to the synergistic effect between strong interfacial coupling and hollow core–shell structure, the Cu2S@C composite can deliver an improved Na+ storage performance. At the high current density of 1.0 A/g, the Cu2S@C anode could exhibit a specific capacity of 100.08 mAh/g, which is significant ameliorative than Cu2S counterpart (only 11.6 mAh/g).

Core/shell Ni@C particle-supported N-doped carbon with hollow capsules for efficient electrocatalytic reduction of oxygen

To replace the noble metal catalysts for oxygen reduction reaction (ORR), a Ni@C-supported N-doped carbon material (Ni@C/NC) is in-situ prepared via one-step pyrolyzing the polymerizable ionic liquid of vinyl imidazole combined with Ni(NO3)2. Systemic investigations demonstrate that these nanosized Ni particles are tightly wrapped with a thin carbon layer to form the core/shell structure, meanwhile carbon capsules are synchronously yielded on the carbon matrix. As a result, both the carbon shell and the carbon capsule jointly increase the active sites of the Ni@C/NC, while the carbon shell also contributes the fast electron-transfer from Ni particle. Compared with the normal Ni-supported carbon catalyst, the Ni@C/NC shows the respectable ORR performance with the onset and half-wave potentials of 0.96 and 0.84 VRHE. After the long-term electrocatalysis (10 h), the Ni@C/NC is found to possess the great structural and electrocatalytic stabilities, which maintains 93 % of the initial current density and the well-dispersed and uniform Ni@C particles. Subsequently, a Zn-Air battery with the Ni@C/NC cathode is assembled and exhibits a peak power density of 200 mW cm−2. Therefore, the as-obtained Ni@C/NC with the high electroactivity and stability can be expected as an ideal candidate to apply in the metal-air batteries and fuel cells in the future.

Analysis of carbon shell of billets with high casting speed

Abstract The increasing casting speed of billets is beneficial for improving single-machine production efficiency, reducing refractory material consumption, and achieving energy conservation and consumption reduction. However, as the casting speed increases, the probability of steel leakage also increases. An analysis of the thickness of the billet shell under high casting speed allows us to analyze the reasons for steel leakage and propose targeted solutions. This article analyzes the steel leakage billet shell of grade 40 steel and concludes that the thickness of the billet shell is between 8-20 mm at the upper of the mold, and only 5-10 mm at the lower of the mold. At the beginning of its formation, the shell of the cast billet is not uniform, with a maximum difference of up to 8 mm. As the casting progresses, the shell of the billet actually becomes thinner. At a distance of 100-200 mm from the mold, the maximum air gap between the billet shell and the copper tube reaches about 5.5 mm. The air gap reduces the uniformity of heat transfer, resulting in an uneven billet shell. After the liquid steel is injected into the shell, it will cause remelting of the solidification shell, resulting in thinning of the casting shell and causing steel leakage at the outlet of the mold.

Preparation and anti-oxidation performance of TaC-SiC nanocomposites by precursor-derived ceramic method

As a kind of ultra-high temperature ceramic, TaC is widely used in aerospace field. In order to improve its high temperature oxidation resistance, SiC is usually added as a second phase. TaC-SiC nanocomposites prepared by precursor-derived ceramic method have the advantages of low pyrolysis temperature, small particle size and uniform phase composition. Some studies have used solid polycarbosilane (PCS) as the precursor of SiC. However, it has problems such as high cost and need to add solvent. In this work, TaC-SiC nanocomposites were prepared by precursor-derived ceramic method with polytantaloxane (PTO) and vinyl-containing liquid polycarbosilane (LPVCS) instead of PCS as raw materials after 2 h pyrolysis at 1600 °C. The obtained TaC-SiC nanocomposites have a particle size of about 200 nm and a grain size of 15–40 nm, wrapped by 1–2 nm amorphous carbon shells, which is beneficial to inhibit grain growth. By analyzing the oxidation mechanism of TaC-SiC nanocomposites, it was found that higher SiC content was conducive to antioxidant, because the SiO2 protective layer formed by oxidation insulated O2 diffusion.

SnS/C nanostructures endowed by low-temperature in-situ carbothermal reduction of sustainable lignin for stable lithium- and sodium-ion storage

SnS emerges as a promising anode candidate for high-energy–density lithium/sodium-ion batteries, attributed to its substantial theoretical capacity of 1022 mAh/g. However, its practical application faces challenges stemming from intrinsic low conductivity and substantial volume variation during lithium/sodium intercalation and deintercalation processes. To address these limitations, we present a cost-effective hydrothermal synthesis combined with an in-situ carbothermal reduction approach for fabricating a nanoflower-like porous carbon-wrapped SnS (SnS/C NFs) anode. The porous carbon shell mitigates the volume expansion of SnS and enhances electronic/ionic conductivity, owing to the porous structure and formation of C-S-C bonds. The SnS/C NFs anode delivered excellent rate performance and long-term cycling stability with high specific capacity both in LIBs (1120 mAh/g after 1000 cycles at 1 A/g) and SIBs (399.3 mAh/g after 500 cycles at 1 A/g). This work provides a safe and low-cost approach for next-generation advanced LIBs and SIBs anodes.

Differences between potassium and sodium incorporation in foraminiferal shell carbonate

Differences between potassium and sodium incorporation in foraminiferal shell carbonate

Hollow Co3O4 nanoparticles on CNF with polydopamine assistance for enhanced supercapacitor electrodes

Transition metal oxides (TMOs) are increasingly recognized as viable cathode materials for pseudocapacitors, due to their substantial theoretical capacity, widespread availability, and environmental benignity. However, their practical application is hindered by significant volumetric expansion during reactions and their inherently limited electrical conductivity. The design of hollow nanoarchitectures, coupled with carbonaceous material integration, has emerged as a potent approach to surmount these limitations. Herein, we reported a stepwise synthesis method where Cobalt oxide (Co3O4) nanoparticles, anchored onto carbon nanofibers (CNF) pre-modified with Polydopamine (PDA) known for its superior adhesion, were transformed into HCo3O4@C@CNF composite materials via a high-temperature annealing process. The mass ratio of Co3O4 to CNF was optimized, with a 3:1 ratio being identified as ideal. This optimized HCo3O4@C@CNF electrode exhibited outstanding electrochemical performance, attaining a significant specific capacitance of 2992 F g-1 at 3 A g-1 and maintaining a 91% capacitance retention rate following 8000 charge-discharge cycles. The CNF acted as an efficient conductive network, substantially enhancing the electrical conductance. Furthermore, the incorporation of PDA facilitated a more uniform dispersion and substantial loading of Co3O4, while the carbon shell, formed upon carbonization, effectively prevented the agglomeration of HCo3O4 nanoparticles, enhancing the overall stability and performance of the electrode. Therefore, the synthesized HCo3O4@C@CNF electrodes exhibit a viable approach for the preparation of electrode materials with high-performance.

A dual-layer solid electrolyte interphase enhances interfacial chemistry stability in aqueous aluminium metal batteries

Aqueous aluminum metal batteries (AAMBs) have garnered significant attention owing to the abundance of aluminum, high volumetric energy density (8040 mAh cm−3, approximately four times that of lithium metal anodes), and chemical inertness. However, profound issues such as surface corrosion and the side reaction of hydrogen evolution severely impede the advancement of AAMBs. Here, we report the in-situ formation of a dense inorganic AlF3 + Al/Zn-CO3 + flexible carbon shell solid-electrolyte interface (SEI) on the surface of an Al electrode through hydrothermal and electrochemical activation in a dilute aqueous solution of Al(OTf)3-Zn(NO3)2. Experimental evidence demonstrates that the electrically insulating Al/Zn-NO3 layer initially forms on the Al negative electrode surface through self-polymerization reactions of Al with Zn2+ and NO3– under sealed heating conditions. Subsequent electrochemical activation leads to the decomposition of CF3SO3- to form conductive AlF3 + Al/Zn-CO3, while in situ generation of a flexible carbon layer occurs internally on the surface. The inorganic inner layer facilitates the diffusion of Al ions, while the organic carbon shell suppresses water permeation and maintains the stability of the SEI structure. The in-situ formed SEI enables the Al//Ti battery to achieve a high Coulombic efficiency (CE) of 98.9 % over 100 cycles. Constructing the Al//β-MnO2 battery yields a high energy density of 216 Wh kg−1, with the capacity retention remaining stable at 83.6 % after 700 cycles.