Carbon Shell Structure Research Articles

Core-Shell MnFe Nanocatalyst Derived from Prussian Blue Analogs for Peroxymonosulfate Activation: Nonradical Mechanism and Bimetallic Valence Cycle.

Sulfamethazine (SAT) is widely present in sediment, soil, rivers, and groundwater. Unfortunately, traditional water treatment technologies are inefficient at eliminating SAT from contaminated water. Therefore, developing an effective and ecologically friendly treatment procedure to effectively remove SAT is critical. This has raised concerns about its potential impact on the environment and human health. In this study, metal-organic-inorganic composites consisting of graphene-encapsulated Fe-Mn metal catalyst (Mn3Fe1-NC) were synthesized by calcining MnFe Prussian blue analogs (PBA) under a nitrogen atmosphere. The composites were applied to activate peroxymonosulfate (PMS) and facilitate the degradation of SAT in aquatic environments. The Mn3Fe1-NC, dosed with 5 mg, in combination with PMS, dosed with 1.5 mmol L-1, achieved a 91.8% degradation efficiency of SAT. The transformation of the CN skeleton led to the formation of a carbon shell structure, which consequently reduced metal ion leaching from the material. At various pH levels, the iron and manganese ions were observed to leach out at levels lower than 0.1392 and 0.0580 mg L-1, respectively. In contrast, the Mn3Fe1-NC was found to be minimally impacted by pH levels and coexisting ions present in the aqueous environment. Radical burst experiments and electrochemical analysis tests verified that degradation primarily occurs through the nonradical pathway of electron transfer. The active sites responsible for this process were identified as the Mn (IV) and graphitic-N atoms on the material, which facilitate direct electron transfer. Additionally, the presence of Fe atoms promotes the valence cycling of Mn atoms. This study introduces new insights into the reaction mechanism and the constitutive relationship of catalytic centers in nonradical oxidation reactions.

Regulating the carbon shell structure of hollow cubic carbon for high performance electromagnetic wave absorption

Herein, HCCs absorbers were synthesized by pyrolysis of phenolic resin, which was uniformly spread onto the surface of NaCl crystals. An investigation was undertaken to assess the effect of shell thickness on wave-absorbing capacity by altering the timing of the phenolic resin reaction. The morphology, composition and electromagnetic properties of the samples were also analyzed for different reaction times. Scanning electron microscopy (SEM) findings revealed a progressive increase in shell thickness of the HCCs from 28.728 nm to 92.654 nm, accompanied by a gradual enlargement in sample size. Compared to samples obtained at other reaction times, the sample reacted for 48 h exhibited favorable wave absorption properties attributed to its fitting shell thickness and impedance matching. Specifically, at a load rate of 5 wt% and the thickness of 2.7 mm, the maximum reflection loss reaches −50.5 dB with an effective absorption bandwidth of 6.2 GHz (11.8 GHz–18.0 GHz). Thus by altering the synthesis duration of phenolic resin is possible to effectively adjust the carbon shell morphology, thereby enhancing the capability for electromagnetic wave absorption.

Structural Engineering of Hard-Soft Carbon Hybrid Anodes for Ultrafast and Ultradurable Potassium-Ion Storage.

Hard-soft carbon hybrid materials, harvesting the expanded interlayer spacing of hard carbon and the high conductivity of soft carbon, hold great promise as anode materials for potassium-ion batteries, but efficient and precise structural control remains a major challenge. Herein, hollow porous bowl-like hard-soft carbon hybrid materials (BHSCs) are facilely synthesized by an in situ hard-template strategy. It is found that the outer and inner walls of the hard carbon bowls are uniformly wrapped by graphene-like soft carbon, which accelerates electron transport and promotes the insertion of potassium ions. Finite element simulation further reveals that the soft-hard-soft carbon shell structure releases stress during the insertion of potassium ions. As a result, BHSC anode exhibits an extraordinary rate capability (209mAh g-1 at 10A g-1) and excellent cycle stability with a capacity of 208mAh g-1 after 5000 cycles at 2A g-1. Impressively, the as-assembled potassium-ion hybrid capacitor based on BHSC anode delivers a great energy/power density (116Wh kg-1/12980W kg-1) and outstanding capacity retention of 83% after 8000 cycles. This work provides guidance for rational structural design of hard-soft carbon hybrid materials to improve their potassium-ion storage performance.

Enhanced nitenpyram degradation by metallic carbon nitrogen composites catalyzed peroxymonosulfate: Synergistic effect of radical and nonradical pathways

Identifying the key active site for peroxymonosulfate (PMS) activation in metallic carbon nitrogen mixtures (MCN) is essential for the optimization of catalyst preparation strategy. Herein, we utilized a pyrolysis method to fabricate MCN for peroxymonosulfate (PMS) activation. The optimal MCN − 700/PMS system showed outstanding catalytic activity for multiple pollutants, and strong resistance to pH (3–11) and complex water environment. Combined with density functional theory calculations, we confirmed the structure − function relationships between different active sites in MCN and PMS. PMS would be preferentially adsorbed on Mn5C2 and Fe2N of MCN − 700, followed by the stretch and fracture of peroxides O − O of the adsorbed PMS. The superior stability could be attributed to that MCN has a continuous N − doped carbon shell structure that promoted electron transfer and encapsulated metal components like an armor. The MCN − 700/PMS system possessed extraordinary degradation activity in complex aqueous environment and various refractory organic pollutants can be efficiently removed, exhibiting the great merits of the radical and nonradical synergistic oxidation. The findings provided new insights into the reaction mechanisms of MCN/PMS system and the rational design heterogeneous PMS systems involving the synergistic action of radical and nonradical oxidation.

Cytomembrane-inspired engineering of oxygen transfer channel for modulating Ni/NiO heterostructure and boosting water oxidation

Development of low-cost and efficient non-precious metal electrocatalysts for oxygen evolution reaction (OER) is of predominant importance for promoting the large-scale application of water splitting. Herein, we use ZIF-8 as a sacrifice template, and successfully prepare the freestanding N-doped carbon nanofibers that decorated with Ni/NiO nanoparticles (denoted as xNi/NiO-NCNFs) via a scalable electrospinning-pyrolysis strategy. Inspired by the cytomembrane, we tune the dosage of ZIF-8 (x) to optimize the amount of micropores on the carbon layer that encapsulating the Ni species, which could act as oxygen transfer channels and enable suitable amount of oxygen to input to modulate the oxidation state of Ni. Moreover, the porous structure could facilitate the mass transfer of the reactants and contact with the active sites, as well as provide more channels for oxygen to release during the OER process. Benefiting from the synergistic effect of the Ni/NiO active sites, porous structure of carbon shell, and the doped N atoms, the 0.075Ni/NiO-NCNFs presents an ultralow overpotential of 210 mV to achieve a current density of 20 mA cm−2 in 0.1 M KOH solution and a low Tafel slope of 29.6 mV dec-1. This work provides a simple and cost-effective pathway to develop porous free-standing non-noble metal-based catalyst with high OER efficiency for potential sustainable electrochemical energy conversion.

N/O‐co‐doped Carbon Shell Structures Loaded with Iron Phthalocyanine for Oxygen Reduction Catalysis

AbstractMetal phthalocyanines (MPcs) have highly conjugated π electron systems and metal atoms acting as active centers, and so exhibit excellent electrocatalytic performance during the oxygen reduction reaction (ORR). However, these complexes also tend to undergo aggregation and exhibit poor electrical conductivity and minimal durability, all of which hinder their large‐scale industrial applications. In the present study, iron phthalocyanine (FePc) is applied to hollow carbon shells (HCSs) to generate an ORR catalyst containing single Fe atoms(HCS‐O‐FePc). The HCSs have numerous N/O‐based surface functional groups that promote the formation of Fe−O bonds with the FePc held in an axial coordination position. These axial Fe−O bonds disrupt the electron symmetry in the plane of the FePc molecules, which facilitate electron transfer. 1100HCS‐O‐FePc exhibits an onset potential of 0.98 V (vs RHE), a half‐wave potential of 0.91 V (vs RHE), an electron transfer number of 3.90, and durability better than that of a 20 % commercial Pt/C catalyst. Electrochemical impedance spectroscopy demonstrates that the ORR process over this material likely proceeds via a rapid 2+2 electron mechanism. This composite displays excellent oxygen reduction properties and is a promising alternative to Pt‐based ORR catalysts.

Carbon Shell‐Encapsulated Metal Alloy Catalysts with Pt‐Rich Surfaces for Selective Hydrogen Oxidation Reaction

AbstractThe performance of polymer electrolyte membrane fuel cells (PEMFCs) is deteriorated by the occurrence of reverse current flow. To suppress the reverse current flow, a hydrogen oxidation reaction (HOR)‐selective catalyst based on the molecular sieve effect should be developed. Here, considering the carbon solubility in transition metals, carbon shell‐encapsulated metal alloy nanoparticles with superior HOR selectivity were fabricated using carbon source in metal precursors. In particular, we introduced carbon solubility as the important parameter that should be considered in the catalyst design. Using Pt and Co with different carbon solubility, as a model catalyst, the effect of the metal composition of the core material on the carbon shell structure was discussed in detail. Due to the formation of high‐density carbon shell and Pt‐rich surface on the alloy nanoparticle, the HOR selectivity was remarkably enhanced. Therefore, this study provides insights into the development of carbon shell‐encapsulated nanoparticles for reaction‐selective catalysis.

Nitrogen-rich soybean protein isolate derived “Self-Doping” carbon nano-onions for luminescence properties

Carbon nano-onions (CNOs) were successfully obtained for the first time through a simple one-pot Microwave hydrothermal carbonization (MHTC) method at low temperature by using biomass macromolecules as the raw materials. The effects of different reaction temperatures and residence times on the characteristics and yield of CNOs were studied. High-resolution transmission electron microscopy (HRTEM) images reveal CNOs with a regular concentric carbon shell structure with 10–20 layers, obvious crystal characteristics, and the lattice spacing of 0.34 nm. X-ray photoelectron spectroscopy and photoluminescence spectroscopy were applied to reveal the effects of different nitrogen forms and hybrid structures of carbon on the fluorescence properties of CNOs. Results showed that reaction temperature affected the structure of CNOs mainly by regulating the degree of carbonization, and residence time mainly affected the aromatization of CNOs. In addition, nitrogen self-doping CNOs prepared at low temperature also have good fluorescence performance. Most strikingly, the stable blue light emission by nitrogen self-doping CNOs could be the combination of the fluorescence of the carbon shell sp2 structure and that of surface functional groups. Taking advantage of the above unique fluorescent behavior, CNOs are prepared as fluorescent anticounterfeiting printing to achieve data encryption and decryption.

Protection and confinement effect of carbon on Co/CoxOy nano-catalyst for efficient NaBH4 hydrolysis

The hydrolysis of sodium borohydride (NaBH4) over catalysts is a promising method to produce hydrogen. Although Co-based catalysts exhibit high activity for NaBH4 hydrolysis, they are still far from satisfying practical applications, especially their poor durability in alkaline media. Herein, a carbon shell structure was designed and synthesized to improve the stability of the mixture of Co0 and CoxOy nanofilms (Co/CoxOy@C) during NaBH4 hydrolysis via a facile polymerization-pyrolysis strategy with Co/CoxOy nanofilms as the precursor. As a result, the Co/CoxOy@C catalyst can achieve a remarkable H2 generation rate of 4348.6 mL min−1 gCo−1 with a low activation energy of 43.6 kJ mol−1, which is superior to most previously reported catalysts. Moreover, the catalyst shows high stability with an H2 generation-specific rate of 79% after five cycles. The excellent performance of carbon substrate can well prevent the agglomeration of Co-based nanoparticle and improve the corrosion resistance of the active Co to BO2− and OH−. This work would widen the road for the preparation of nanoconfined catalysts, which has prospective application potentials for H2 production from NaBH4 hydrolysis.

A bimetallic ZIFs-triggered hierarchical carbon structure for stabilized silicon anode

The application of silicon-based anode remains a serious challenge due to its intrinsic volumetric expansion effect and low conductivity. In our work, a novel CNT-interspersed hierarchical carbon shell structure (denoted as PDA@CoZn-NC@Si) is synthesized by wrapping Si uniformly in the bimetallic zeolite imidazolate frameworks (ZIFs) and then encapsulated with a dopamine-derived carbon shell. The PDA@CoZn-NC@Si anode delivers better cycle stability of 814 mAh/g at 0.5C for 400 cycles (only −0.14% capacity reduction per cycle) and possesses excellent rate capability, which benefits from the inner porous buffer spaces, interspersed CNT, and solid heterogeneous carbon shells. In addition, the full cell is assembled by pairing a solution-based chemically prelithiated PDA@CoZn-NC@Si anode with a Li(Ni1/3Co1/3Mn1/3)O2 (NCM111) cathode, and it presents an improved initial coulombic efficiency (88.3%) and a high energy density (419.8 Wh/kg). This study provides effective guidance for optimizing the microstructure design and prelithium of Si-based anodes.

Dual Metal-Loaded Porous Carbon Materials Derived from Silk Fibroin as Bifunctional Electrocatalysts for Hydrogen Evolution Reaction and Oxygen Evolution Reaction.

Developing electrocatalysts with high efficiency and long-term stability for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is significant to massively generate hydrogen energy by water splitting. In this work, cobalt and tungsten dual metal-loaded N-doped porous carbon electrocatalysts derived from silk fibroin were successfully prepared through facile carbonization and chemical activation by KCl and applied as efficient electrocatalysts for HER and OER. After chemical activation, the resulting catalysts present a unique hierarchical porous structure with micro-, meso-, and macropores, which is able to expose more implantation sites for catalytic active metals and will in turn promote the efficient diffusion of the electrolyte. The catalyst under the optimized condition (CoW@ACSF) has a specific area of 326.01 m2 g-1. The overpotential at a current density of 10 mA cm -2 of CoW@ACSF is 138.42 ± 10.39 mV toward HER and 492.05 ± 19.04 mV toward OER. Furthermore, the overpotential only increases 101.2 mV toward HER and 66.00 mV toward OER after the long-term stability test of chronopotentiometric test over 10 h, which confirms the excellent stability of the CoW@ACSF, owing to its unique carbon shell structure. This work gives an insight into the design and engineering of silk fibroin-derived carbon materials for electrocatalysis toward HER and OER.

Antimony doped SnO2 nanowire@C core–shell structure as a high-performance anode material for lithium-ion battery

SnO2 is considered as one of the high specific capacity anode materials for Lithium-ion batteries. However, the low electrical conductivity of SnO2 limits its applications. This manuscript reports a simple and efficient approach for the synthesis of Sb-doped SnO2 nanowires (NWs) core and carbon shell structure which effectively enhances the electrical conductivity and electrochemical performance of SnO2 nanostructures. Sb doping was performed during the vapor-liquid-solid synthesis of SnO2 NWs in a horizontal furnace. Subsequently, carbon nanolayer was coated on the NWs using the DC Plasma Enhanced Chemical Vapor Deposition approach. The carbon-coated shell improves the Solid-Electrolyte Interphase stability and alleviates the volume expansion of the anode electrode during charging and discharging. The Sb-doped SnO2 core carbon shell anode showed the superior specific capacity of 585 mAhg−1 after 100 cycles at the current density of 100 mA g−1, compared to the pure SnO2 NWs electrode. The cycle stability evaluation revealed that the discharge capacity of pure SnO2 NWs and Sb doped SnO2 NWs electrodes were dropped to 52 and 152 mAh g−1 after100th cycles. The process of Sb doping and carbon nano shielding of SnO2 nanostructures is proposed for noticeable improvement of the anode performance for SnO2 based materials.

A target-customized carbon shell structure of carbon-encapsulated metal nanoparticles for fuel cell applications

We uncover the secrets to controlling the carbon shell structure on the surface of metal nanoparticles at the sub-nm scale to improve the performance and durability of fuel cells.

Metal-carbon mesocomposites application possibilities as the medicine magnetic transport within an organism

The paper is dedicated to the consideration of the metal-carbon mesocomposites application possibilities for the medicine magnetic transport. This trend is determined by correspondent peculiarities of content and structure of mesoscopic composites. The main peculiarities of these nanosized particles are the following: a) the presence of unpaired electrons on the carbon shell; b) the structure of carbon shell from poly acetylene and carbine fragments; c) the atomic magnetic moment of inner metal is equaled to more than 1–3 μB. The creation of reactive mesoscopic materials with regulated magnetic characteristics which can find application as medicine magnetic transport within an organism is very topical. The present investigation has fundamental character. It’s based on the ideas concerning to the change of metal-carbon mesocomposites reactivity. The use is possible as metal-carbon mesocomposites both and they are modified analogously.

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).

Rational Assembly of Hierarchically Porous CoxFe1–xS2@Carbon Superparticles for Efficient Hydrogen Evolution

Electrochemical water splitting is a highly promising strategy to produce high purity hydrogen. To reduce costs, it is critical to develop non-precious-metal catalysts displaying high catalytic activity toward the hydrogen evolution reaction (HER). Here, we develop a flexible approach to synthesize hierarchically porous CoxFe1–xS2@carbon (x ≈ 0.36) superparticles with mesopores, macropores, and carbon shell structures. CoxFe1–xS2@carbon superparticles exhibited excellent HER activity and catalytic stability.

Tailor of high performance electrocatalyst for oxygen reduction reaction through rational structural adjustment of carbon-based architecture

The shortage of high effective and reliable cathode catalysts with desirable performance for oxygen reduction needs to be addressed to accelerate the large-scale expansion of clean and sustainable fuel cells. Herein, we report a facile hydrothermal route to tailor a new type of N, P co-doped carbon architecture with Fe2P nanoparticles embedded/encapsulated in the crumped carbon nanosheets. The rational design of carbon shell structure in strong interaction with rGO endows the catalyst with graphitic-N abundance, mesoporous structure dominance and active Fe2P isolation. We propose the pyrolyzed dicyandiamide-derived carbon fragment as not only an additional nitrogen resource but a favorable micro-structured separator and protective porous layer for metal agglomeration and demetallation, which ensures the catalyst with excellent activity and stability. The co-doped carbon shows excellent activity with positive half-wave potential of +0.823 V via complete 4 electron pathway, close to that of Pt/C material (+0.831 V). The inspiring durability is confirmed by merely 2 mV negative potential shifts after 1000 cycles of CV tests. In the end, this paper provides a promising way to develop a high effective carbon-based bifunctional catalyst for both oxygen reduction and evolution reactions through electronic design and structural engineering.

Modulating Catalytic Activity and Durability of PtFe Alloy Catalysts for Oxygen Reduction Reaction Through Controlled Carbon Shell Formation.

Demand on synthetic approaches to high performance electrocatalyst with enhanced durability is increasing for fuel cell applications. In this work, we present a facile synthesis of carbon shell-coated PtFe nanoparticles by using acetylacetonates in metal precursors as carbon sources without an additional polymer coating process for the carbon shell formation. The carbon shell structure is systematically controlled by changing the annealing conditions such as the temperature and gas atmosphere. PtFe catalysts annealed at 700 °C under H2-mixed N2 gas show much higher oxygen reduction reaction (ORR) activity and superior durability compared to a Pt catalyst due to the ultrathin and porous carbon shells. In addition, when increasing the annealing temperature, the carbon shells encapsulating the PtFe nanoparticles improves the durability of the catalysts due to the enhanced crystallinity of the carbon shells. Therefore, it is demonstrated that the developed hybrid catalyst structure with the carbon shells not only allows the access of reactant molecules to the active sites for oxygen reduction reaction but also prevents the agglomeration of metal nanoparticles on carbon supports, even under harsh operating conditions. The proposed synthetic approach and catalyst structure are expected to provide more insights into the development of highly active and durable catalysts for practical fuel cell applications.

Synthesis of cage-like silicon/carbon microspheres and their high-rate performance anode materials for lithium-ion batteries

The practical application of Si-based materials has been impeded by poor cycling stability. The cage-like silicon/carbon microspheres were fabricated via a series of procedures: the allometric nucleation, magnesiothermic reduction and selective etching. The microstructure, morphology and electrochemical performance for cage-like silicon/carbon microspheres were investigated by X-ray photoelectron spectra, scanning electron microscopy, transmission electron microscopy and galvanostatic charge-discharge tests. The cage-like carbon shell can effectively absorb the volume expansion and restrain the pulverization for silicon electrodes due to its excellent flexibility and toughness, and particular structure. The cage-like silicon/carbon microspheres reveal an outstanding charge capacity of 1926 mA h g−1 at 0.1 C, and still remain 1790 mA h g−1 after 200 cycles. They exhibit an excellent rate capacity of 916 mA h g−1 and capacity retention of 96% after 1000 cycles at 5 C. The design strategy of the cage-like carbon shell structure offers a novel path for improving the electrochemical performance of silicon-based materials.

Phase transformation and carbon precipitation of coal fly ash magnetospheres during a CVD process for microwave adsorption

Abstract Coal fly ash is industrial waste produced by coal power plants, containing large amounts of magnetospheres (MSs), where Fe3O4 is abundant and magnetite is the major composition. However, the functional reuses of MSs are always restricted by the impurities of aluminosilicate and other forms of iron oxide including maghemite, magnesioferrite, as well as hematite. In this paper, a chemical vapor deposition (CVD) process was proposed to convert MSs into a magnetic core@ carbon shell structure, which would found its application in microwave adsorption field. The prepared samples were characterized by using SEM, HRTEM, EDX, BET, XRD, Raman spectroscopy and TGA analysis. Results showed that MSs burst during the CVD process and transformed into a loose agglomeration of submicron-sized particles with a typical core@ shell structure. Crucially, instead of single sphere of MSs, the ultrafine grains of ferrospinel within MSs served as the core. The mechanism of carbon deposition of graphite shells and phase transformation of ferrospinel cores during the CVD process were revealed. Magnetism and microwave adsorption properties were tested, and the structural dependence relationship between these properties and the core@ shell structure was clearly identified. For a sample time of 60 min, the minimum absorption peak was observed as −32.4 dB at 12 GHz, with the minimum frequency bandwidth below −10 dB at 4.3 GHz. We propose a low-cost, one-step preparation of cementite core@ graphite shell composites with high-performing microwave adsorption. Our method provides an alternative option for the practical reuse of the industrial waste.