Hierarchical Core-shell Structure Research Articles

Synergistic S-doped biomass carbon and N-doped carbon for construction of interlayer expanded MoS2 core/shell nanospheres for potassium and sodium storage

The construction of high-performance anode materials is the critical technology for promoting the development and application for potassium-ion batteries (PIBs). Herein, we present the synthesis of S-doped biomass carbon/MoS2@N-doped carbon core-shell nanospheres with the expanded interlayer of 0.99 nm (S-BC/E-MoS2@N-C) via the combined hydrothermal and polymerized method. In the hydrothermal process, we firstly find that the biomass carbon is heteroatomic doped with sulfur in the hydrothermal process by the sulfur source for forming MoS2. The polymerized N-doped carbon is forming on surface of MoS2 nanosheets for construction sandwiched core-shell structure. The N-doped carbon layer and S-doped biomass carbon use cooperatively to establish an omnibearing conductive network on MoS2 by internal and external integration. In such a unique structure, high conductivity and excellent structural stability are achieved in the S-BC/E-MoS2@N-C composite. Consequently, the S-BC/E-MoS2@N-C electrodes exhibit superior potassium storage performances including enhanced rate capability and good cycled stability with high reversible capacities (156.6 mA h g−1 after 650 cycles at 100 mA g−1). And for sodium ion batteries, the S-BC/E-MoS2@N-C electrode delivers an initial reversible capacity of 538.9 mAh g−1 at 200 mA g−1 and maintains 371.1 mAh g−1 after 200 cycles. This work shed a kind of double heteratomic doping and core-shell hierarchical structure of MoS2 anodes in potassium/sodium storage.

A novel non-enzymatic electrochemical sensor based on NiS/Co3S4@h-Ni NWs core-shell electrode for glucose detection in human serum

To obtain a non-enzymatic electrochemical sensor with good performance such as sensitivity, selectivity, and stability, fine-tuning and rational design of the electrocatalytic material are essential. In this study, a novel catalyst (NiS/Co3S4@h-Ni NWs) with a hierarchical core-shell structure was synthesized in two steps to be used as a non-enzymatic electrode for glucose detection. First, hierarchical nickel nanowires, h-Ni NWs (the core), were prepared by the reduction of Ni2+ ions by hydrazine N2H4, and then the h-Ni NWs are covered with NiS/Co3S4 (the shell) by the hydrothermal method. The resulting NiS/Co3S4@h-Ni NWs showed a core-shell structure with abundant nanotides on the surface and good crystallinity. The prepared sensor exhibited two linearity ranges in the glucose concentration ranges of 0.001–6.57 mM and 6.57–13.32 mM with a sensitivity of 1171.9 μA mM−1 cm−2 and 316.5 μA mM−1.cm−2, respectively, and with a low detection limit of 0.13 μM (S/N = 3) due to its developed core-shell structure that provides excellent conductivity, an efficient mesoporous network, and suitable channels for rapid ion/electron transfer for electrocatalytic activity. In addition, the sensor also showed exceptional selectivity against coexistence interference, good long-term stability, reproducibility, and repeatability. All these excellent results show that the prepared NiS/Co3S4@h-Ni NWs catalyst can be a promising electrode material for glucose detection.

Template‐Free Synthesis of Phosphorus‐Doped g‐C3N4 Micro‐Tubes with Hierarchical Core–Shell Structure for High‐Efficient Visible Light Responsive Catalysis

This work reports a new form of tubular g-C3 N4 that is featured with a hierarchical core-shell structure introduced with phosphorous elements and nitrogen vacancies. The core is self-arranged with randomly stacked g-C3 N4 ultra-thin nanosheets along the axial direction. This unique structure significantly benefits electron/hole separation and visible-light harvesting. A superior performance for the photodegradation of rhodamine B and tetracycline hydrochloride is demonstrated under low intensity visible light. This photocatalyst also exhibits an excellent hydrogen evolution rate (3631 µmol h-1 g-1 ) under visible light. Realizing this structure just requires the introduction of phytic acid into the solution of melamine and urea during hydrothermal treatment. In this complex system, phytic acid plays as the electron donor to stabilize melamine/cyanuric acid precursor via coordination interaction. Calcination at 550°C directly renders the transformation of precursor into such hierarchical structure. This process is facile and shows the strong potential toward mass production for real applications.

Intense red-emitting core-active shell SiO2@CaAl2O4:Eu3+ surface sensitive fluorescent probe for dactylography applications

Rational design and synthesis of hierarchical core-shell structures have been regarded as an operative approach to enhancing the luminescence performance of the phosphors. In this work, intense red-emitting CaAl2O4:Eu3+(1–9 mol %) nanophosphors and SiO2@CaAl2O4:Eu3+(7 mol %) structures were fabricated by the ultrasound-assisted sonochemical route. The powdered x-ray diffraction studies of prepared core-shell structure confirm the monoclinic phase of the CaAl2O4 layer and amorphous SiO2 cores. The morphological and elemental analysis clearly evidences the formation of spherical and uniform core-shell structures. Upon 463 nm excitation, the photoluminescence emission spectra of CaAl2O4:Eu3+(1–9 mol %) nanophosphors consist intensive and sharp peaks at ∼ 507, 532, 551, 615, 654, 702 and 759 nm, owing to 5D1→7F2, 5D0→7F0, 5D0→7F1, 5D0→7F2, 5D0→7F3, 5D0→7F4 and 5D0→7F5 transitions of Eu3+ ions, respectively. Almost 1.6-fold enhancement in the emission intensity without any change in the spectral shape was noticed in core-shell SiO2@CaAl2O4:Eu3+(7 mol %) structures as compared to CaAl2O4:Eu3+ (7 mol %) nanophosphor, which attributed to the improved surface area, diminished surface defects and surface hanging bonds. The photometric properties signify the pure red emission of the structures and are useful for multi-functional applications. The prepared spherical and uniform-sized core-shell structures are used as fluorescent labeling material for the visualization of latent fingerprints on various surfaces. The fingerprints developed using prepared structures show excellent contrast, high sensitivity, and negligible background disruption. This work demonstrated that the synthesized core-shell structures are a versatile material and can find their practical applications in solid-state lighting and dactylography.

Boosted degradation of tetracycline over a novel hierarchical 2D/1D S-scheme heterojunction Bi2O4 @SnS under visible light irradiation

Highly efficient photocatalytic degradation of tetracyclines (TCs) has drawn increasing interest in the field of environmental remediation. Constructing S-scheme heterojunction is a desirable strategy for booting the photocatalytic activity of the semiconductors. Herein, rod-like Bi2O4 was decorated with SnS nanosheets with excellent light harvesting ability to construct 2D/1D hierarchical S-scheme heterojunction Bi2O4 @SnS. The photocatalytic degradation of TC over Bi2O4 @SnS was carried out under visible-light. S-scheme interfacial charge transfer mode was inferred via in-situ irradiated X-ray photoelectron spectroscopy (XPS). The optimum Bi2O4 @SnS composites 20-SSBO exhibits excellent photocatalytic activity and stability for degradation of TC in both deionized water and natural river water. Within 120 min, the degradation efficiency of tetracycline reaches 91%. The degradation rate constant of TC over 20-SSBO is 3.3 and 10.6 folds that over Bi2O4 and SnS, respectively. The significant enhancement of photocatalytic activity is mainly due to two aspects: On the one hand, the successful construction of S-scheme heterojunction between Bi2O4 and SnS not only effectively promotes the separation and transfer of photogenerated carriers but also preserves electrons with strong reduction ability and photogenerated holes with strong oxidation ability. On the other hand, the 2D/1D hierarchical core-shell structure resulted in increased specific surface area and broadened visible-light absorption region. In addition, environmental factor such as pH, typical inorganic cations and anions, and natural organic matters have less effect on the photocatalytic degradation of tetracycline. The possible photocatalytic degradation pathway of TC was proposed. The S-scheme heterojunction Bi2O4 @SnS have promising application in natural Environmental remediation.

High-performance metal-oxide gas sensors based on hierarchical core-shell ZnFe2O4 microspheres for detecting 2-chloroethyl ethyl sulfide.

Mustard gas, an erosive chemical agent, is primarily used as a chemical weapon, which seriously threatens human life and health. Therefore, detecting mustard gas and its simulant, 2-chloroethyl ethyl sulfide (2-CEES), is a very important task. As a binary metal oxide with a spinel structure, ZnFe2O4 is widely used for fabricating gas sensors because of its stable chemical structure and abundant oxygen vacancies. In this study, gas-sensing ZnFe2O4 microspheres with a hierarchical core-shell nanosheet structure were prepared via a simple one-step solvothermal method. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and N2 adsorption analyses were performed to characterize the morphology, structure, and chemical composition of these microspheres. A gas sensor was fabricated from the as-synthesized material, and its gas sensing performance was evaluated, using 2-CEES as a target gas. The obtained ZnFe2O4-based sensor exhibited a high sensitivity of 9.07 to 1 ppm 2-CEES at the optimal working temperature of 250 °C. The sensor response and recovery times were 18 and 546 s, respectively, and its detection sensitivity of 2.87 achieved at a 2-CEES concentration of 0.01 ppm was within an acceptable range. Additionally, the sensor demonstrated sufficiently high 2-CEES selectivity, repeatability, and long-term stability.

Bioinspired Tough and Strong Fibers with Hierarchical Core–Shell Structure

AbstractStrong and tough bio‐based fibers are attractive for both fundamental research and practical applications. In this work, strong and tough hierarchical core–shell fibers with cellulose nanofibrils (CNFs) in the core and regenerated silk fibroins (RSFs) in the shell are designed and prepared, mimicking natural spider silks. CNF/RSF core–shell fibers with precisely controlled morphology are continuously wet‐spun using a co‐axial microfluidic device. Highly‐dense non‐covalent interactions are introduced between negatively‐charged CNFs in the core and positively‐charged RSFs in the shell, diminishing the core/shell interface and forming an integral hierarchical fiber. Meanwhile, shearing by microfluidic channels and post‐stretching induce a better ordering of CNFs in the core and RSFs in the shell, while ordered CNFs and RSFs are more densely packed, thus facilitating the formation of non‐covalent interactions within the fiber matrix. Therefore, CNF/RSF core–shell fibers demonstrate excellent mechanical performances; especially after post‐stretching, their tensile strength, tensile strain, Young's modulus, and toughness are up to 635 MPa, 22.4%, 24.0 GPa, and 110 MJ m−3, respectively. In addition, their mechanical properties are barely compromised even at −40 and 60 °C. Static load and dynamic impact tests suggest that CNF/RSF core–shell fibers are strong and tough, making them suitable for advanced structural materials.

A robust octahedral NiCoOxSy core-shell structure decorated with NiWO4 nanoparticles for enhanced electrocatalytic hydrogen evolution reaction

Electrocatalytic hydrogen evolution reaction by water splitting is deemed to a clean and efficient approach for greener energy. The intensive pursuit of cost-effective and stable electrocatalysts for HER is quite imperative and challenging. Herein, a typical core-shell NiWO4@NiCoOxSy/NCF nano-architecture consisted of NiCoOxSy/NCF octahedrons and NiWO4 nanoparticles on nickel-cobalt foam is synthesized, and the NiWO4@NiCoOxSy/NCF requires quite small overpotential of 85 mV to afford current density of 10 mA cm−2 for HER in 1 M KOH, respectively, while NiCoOxSy/NCF shows the overpotential of 132 mV at the current density of 10 mA cm−2 in 0.5 M H2SO4. Moreover, they still present good durability with continuous operation of 72 h in alkaline and acidic electrolytes, outperforming most of the non-noble bimetallic oxides or sulfides electrocatalysts. The prominent performance benefits from NiWO4@NiCoOxSy/NCF takes advantages of component respective strengths such as interfacial cooperative effect, strong electrical connection and fast electron transfer, the highly exposed surface area, in situ surface reconstruction. The work provides a new prospect toward the controlled design and rational fabrication of multicomponent hierarchical core-shell structure electrocatalyst in high-performance flexible electrochemical hydrogen production.

A novel hierarchical core-shell structure of NiCo2O4@NiCo-LDH nanoarrays for higher-performance flexible all-solid-state supercapacitor electrode materials

In the present work a 3D hierarchical NiCo 2 O 4 @NiCo-LDH core-shell structure has been fabricated on activated carbon cloth through a facile hydrothermal strategy and an electrodeposition step. The core of the NiCo 2 O 4 nanowires forms the nanoarray backbone on carbon cloth while the shell of NiCo-LDH nanosheets extends the electrochemical active sites and generates mesoporous hierarchical channels to facilitate electron and ion transport. Therefore, with the optimized mass ratio of 1.9 between NiCo-LDH and NiCo 2 O 4 , such a core-shell structure enhanced the areal capacitance of the as-prepared NiCo 2 O 4 @NiCo-LDH electrode up to 6092 mF/cm 2 (or areal capacity of 0.846 mAh/cm 2 at 2 mA/cm 2 for the battery type pseudocapacitor) and obtain high specific capacitance of 1882 F/g under 1 A/cm 2 . The capacity retention rate can maintain 83.9 % after 5000 cycles at 30 mA/cm 2 . Furthermore, an all-solid-state asymmetric supercapacitor (ASC) was assembled using NiCo 2 O 4 @NiCo-LDH//activated carbon. Such an ASC exhibits a very high energy density of 49 Wh/kg at the power density of 750 W/kg and retains 30 Wh/kg at 7500 W/kg. The ASC shows its excellent cycling stability by keeping 83.3 % of initial capacity retention rate after 2000 cycles under 5 A/g. The assembled flexible all-solid-state supercapacitor with NiCo 2 O 4 @NiCo-LDH//activated carbon exhibits good mechanical stability and high specific capacity of 157 F/g under 1 A/g. The significantly improved electrochemical properties demonstrates the practical applications of the core-shell structure of NiCo 2 O 4 @NiCo-LDH on carbon cloth for novel ASC configuration design and development of next energy storage devices. • The unique NiCo 2 O 4 @NiCo-LDH cover-shell heterostructure greatly improve the electrochemical performance. • The NiCo 2 O 4 @NiCo-LDH//ACC electrode shows the high area capacitance of 6092 mF/cm 2 . • The NiCo 2 O 4 @NiCo-LDH//AC ASC device has good flexibility, high energy density and power density.

CuxO nanorod arrays shelled with CoNi layered double hydroxide nanosheets for enhanced oxygen evolution reaction under alkaline conditions

Exploration of highly efficient and cost-effective oxygen evolution reaction (OER) electrocatalysts is of crucial importance for the development of water splitting. In recent years, Cu-based materials have been widely concerned in OER due to their non-toxicity, rich reserves and highest reversibility. Meanwhile, CuxO nanorods is easy to be prepared in industry. Herein, we report a fast preparation method to construct an integrated CuxO@CoNi-LDH electrocatalyst with a unique 1D nanowire-2D nanosheet hierarchical core–shell structure by electrodepositing CoNi-LDH nanosheet arrays directly onto CuxO nanorods (CuxO were in situ-created on the Cu foam) at a large deposition voltage of −3.0 V vs SCE. The unique heterogeneous core–shell nanostructure, large deposition amount of CoNi-LDH and the synergistic effects between CuxO core and CoNi-LDH shell can provide abundant active sites, rich open-channels and reduced charge transfer resistance (Rct) for effective oxygen release and facile electron transport. Consequently, the optimized CuxO@CoNi-LDH/CF exhibits a low overpotential of 207 mV in 1 M KOH solution at the current density of 10 mV cm−2 and a small Tafel slope of 50.1 mV dec−1. After 60 h of long-term stability test, the catalytic performance is only slightly weakened. This work demonstrates a new approach to design the high-performance LDH and Cu-related OER catalysts by constructing a unique hierarchical core–shell nanostructure.

Hierarchical core-shell structure of ZIF-8 derived porous carbon supported PdZn nanoalloys within mesoporous silica shells as efficient methanol oxidation electrocatalysts

The anodic precious metal catalyst of direct methanol fuel cell (DMFC) is poisoned due to CO adsorption, which makes the methanol oxidation reaction (MOR) kinetics tardily. In this study, a series of hierarchical core–shell structure catalysts PdZn/ZDC@SiO2 were synthesized by loading PdZn nanoparticles (NPs) on ZIF-8 derived porous carbon (ZDC) and protecting by the mesoporous silica (SiO2) are reported. A hierarchical core–shell structure informed in PdZn/ZDC@SiO2(20) caused by mesoporous silica shell leads to well-dispersed and uniform of PdZn NPs (10 nm). Compared with commercial palladium carbon (Pd/C), the optimized catalyst PdZn/ZDC@SiO2(20) has higher current density (765.2 mA/mg) and stronger CO toxicity tolerance (If/Ib = 3.30). And the onset potential and the peak potential of PdZn/ZDC@SiO2(20) (−0.294 V, −0.203 V) are more negative in CO stripping experiment. Silica is an inorganic oxide that can provide oxygen-containing species to the adjoining precious metal sites and promote CO oxidation. In addition, PdZn NPs can accelerated electron transport and then improve methanol oxidation performance due to the changing electronic structure of Pd and the modifying the surface adsorption of the catalyst. PdZn/ZDC@SiO2(20) is a potential substitute material for noble metal catalyst that can be used for direct methanol fuel cells.

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.

Fabrication of hierarchical core–shell carbon microspheres@ layered double hydroxide@ polyphosphazene architecture in flame‐retarding polypropylene

Developing advanced performance polypropylene (PP) composites with less smoke, eco-friendly and efficient flame retardants (FRs) has been a growing focus of research. In particular, it was significant to reduce the emissions of smoke and toxic gases generated during the burning of PP so that it meets green and safe industrial requirements. In this work, a CMSs@LDH@PZN hierarchical core–shell framework was designed and synthesized by using carbon microspheres (CMSs) and layered double hydroxides (LDHs) nanosheets connected to CMSs by electrostatic forces with polyphosphazene (PZN). The structure, composition and morphology of CMSs@LDH@PZN were characterized by SEM, TEM, FT-IR, XRD and TG, and the results were shown the triumphant preparation of the well-designed hierarchical core–shell structure CMSs@LDH@PZN. Additionally, the total smoke production, peak heat release rate and total heat release rate of PP/CMSs@LDH@PZN composites were decreased by 56.2%, 41% and 43.4%, respectively. With the addition of 20 wt% CMSs@LDH@PZN alone, the PP/CMSs@LDH@PZN composites reached a V-0 rating in the Vertical combustion tester (UL-94), and had a limiting oxygen index (LOI) value of 29.6%. Moreover, the heat release and toxic smoke emission were significantly lessened, which can be own to the adsorption of core–shell hybrid materials and the barrier effect of the P and N element crosslinked carbon layer. Herein, this work extends the idea of preparing multipurpose high-performance composites and designs and synthesizes an eco-friendly and efficient flame retardant with a double shell structure.

Three-dimensional hierarchical carbon-incorporated Ni3S2@Mn–Co–S@Co9S8 composite on Ni foam for high-performance hybrid supercapacitors

Construction of multi-component composite electrode materials with unique hierarchical structures is an effective method to manufacture high-performance hybrid supercapacitors (HSCs). In this study, carbon-incorporated multiple metal sulfides-based composite with three-dimensional hierarchical core-shell structure directly grown on the Ni foam (Ni3S2@Mn–Co–S@Co9S8–C/NF) was successfully prepared. The Ni3S2@Mn–Co–S@Co9S8–C combining with Co9S8–C nanoparticles anchored on the substrate of Ni3S2@Mn–Co–S possesses the unique structures of nanoflake and nanospine. The Ni3S2@Mn–Co–S@Co9S8–C/NF electrode with heterogeneous composition and carbon incorporation demonstrates a hierarchical structure. Such features can offer more exposed active sites and redox reactions, and to an extent, it will enhance the electrochemical conductivity, and supply more efficient transfer of charge and ions. As a consequence, the Ni3S2@Mn–Co–S@Co9S8–C/NF exhibits a high specific capacity of 2.16 C cm−2 (617.14C g−1) at 4 mA cm−2 and satisfactory rate performance (76.85% capacity retention from 4 to 20 mA cm−2). Additionally, the assembled Ni3S2@Mn–Co–S@Co9S8–C//active carbon HSC device delivers a maximum energy density of 47.6 Wh kg−1at 805.5 W kg−1 and excellent cycling stability (92.41% capacity retention after 5000 cycles). Such work may provide an attainable strategy to engineer self-standing carbon-incorporated multiple metal sulfides-based electrodes with unique compositions and nanostructures for high-performance HSC devices.

Nonenzymetic glucose sensitive device based on morchella shaped nickel-copper layered double hydroxide

We present a kind of three-dimensional core-shell hierarchical structure based on nickel-copper layered double hydroxide (Ni-Cu LDH), in which the morchella shaped Ni-Cu LDH shells were synthesized on the nanowire-shaped Cu(OH)2 backbones and grown on Cu foam (CuF) substrate (Ni-Cu LDH@Cu(OH)2 NWs/CuF). The as-fabricated nanocomposites were characterized and used for nonenzymetic glucose determination. The sensing properties of Ni-Cu LDH@Cu(OH)2 NWs/CuF were optimized by changing the mole ratio of Ni and Cu, demonstrating the optimized electrode (Ni:Cu = 4:2) has remarkable response/recovery times (1.5/3.5 s towards 200 μM glucose), fine reproducibility and anti-interference properties, as well as anti-bending performance. Furthermore, the as-prepared optimized electrode was used to develop sensitive device by assembling with counter and reference electrodes into polydimethylsiloxane (PDMS)-based micro-cavity. The sensitive device exhibits a high sensitivity of 7.08 μA/μM/cm2, a good linear range of 0.006–1.6 μM, and a detection boundary of 1.3 μM. In addition, the developed device demonstrates good stability and can achieve the determination of glucose in human serum. Therefore, the morchella shaped Ni-Cu LDH hierarchical structures has shown an outstanding performance and can be used for detecting glucose level in serum samples, so it represents a promising sensitive material for constructing enzymeless glucose sensor.

Self-supported ZIF-coated Co2P/V3P bifunctional electrocatalyst for high-efficiency water splitting

Exploring high-efficiency dual-functional electrocatalysts to drive electrochemical water splitting is of great importance for advancement of renewable hydrogen energy. Herein, a hierarchical core–shell structure electrocatalyst ZIF-Co2P/V3P is in situ grown on Ni foam (abbreviated as ZIF-Co2P/V3P@NF) by a stepwise method. Firstly, Co, V layered double hydroxides (CoV-LDHs) is grown directly on Ni foam (NF) substrate by solvothermal method. Secondly, CoV-LDHs@NF is transferred into 2-MeIm solution and its surface is coated with a layer of imidazolate zeolite skeleton (ZIF). Finally, ZIF-Co2P/V3P@NF catalyst is obtained by low-temperature phosphorization method. The performance of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) can be adjusted by tuning molar ratio of Co/V, and the optimized ZIF-Co2P/V3P@NF-2 manifests superior performance due to its core–shell structure covered by ZIF skeleton, rich heterogeneous interfaces, as well as the positive synergistic interaction between the Co2P and V3P. The overpotentials are only 57 mV@10 mA cm−2 for HER and 261 mV@10 mA cm−2 for OER. Remarkably, the alkaline electrolyzer assembled with ZIF-Co2P/V3P@NF-2 catalyst acquires a small operating voltage of 1.54 V to drive the current density of 10 mA cm−2 and displays excellent long-term durability. This work provides a novel opinion for design and preparation of non-noble metal electrocatalysts.

Unique core-shell Co2(OH)2CO3@MOF nanoarrays with remarkably improved cycling life for high performance pseudocapacitors

Binder-free composite electrode material consisted of cobalt hydroxycarbonates (Co2(OH)2CO3) and bimetallic metal-organic-framework (NiCo-MOF) is facilely prepared for the first time through a hydrothermal-solvothermal combined method. The composite Co2(OH)2CO3@MOF presents a unique core-shell architecture, which endows remarkable superiority such as great surface area, short diffusion pathway and component synergy effects, leading to splendid supercapacitor performance. The optimal composite electrode exhibits ultrahigh specific capacitance (3232 F g−1 at 1 A g−1), good rate capability and outstanding cycle life (84.1% after 5000 cycles). In addition, an asymmetric supercapacitor (ASC) device Co2(OH)2CO3@MOF-2//AC (active carbon) delivers a high energy density (55.2 W h kg−1 @ 0.8 kW kg−1) and excellent cycle life (89.2% after 6000 cycles). These values are comparable to or even better than the recently reported related electrode materials in literatures (Table S1), demonstrating the prospect for future high performance energy storage devices. The smart strategy reported here can also be promoted to other metal hydroxycarbonates with advanced hierarchical core-shell structures for high performance electrochemical devices.

Hierarchical core-shell Ni-Co-Cu-Pd alloys for efficient formic acid oxidation reaction with high mass activity

Development of efficient electrocatalyst with a small use of noble metals for formic acid oxidation reaction (FAOR) is the most urgent need in realizing practical direct formic acid fuel cells (DFAFC). Herein, we developed quaternary Ni-Co-Cu-Pd (NCCP) alloys with an intriguing nanostructure, that is, hierarchical core–shell structure, which demonstrates excellent catalytic performance for FAOR with a high mass activity. The mass activity of NCCP for FAOR is 3 folds higher than the benchmark Palladium on Carbon (Pd/C, 10 wt%) catalyst. We reason this exceptionally high mass activity of NCCP to the synergetic effects between the surface decorated Pd nanoclusters and the transition metal cores, resulting in highly disturbed electronic configurations at the surface. In addition, the intriguing nanostructure evolved during FAOR can facilitate atomic, ionic, and molecular transfers during FAOR. The NCCP also demonstrates a high electrocatalytic stability for FAOR, which highlights its potential use for the practical DFAFC.

Stable and enhanced electrochemical performance based on hierarchical core–shell structure of CoMn2O4@Ni3S2 electrode for hybrid supercapacitor

Herein, accessible and low-cost CoMn2O4@Ni3S2 core–shell nanoneedle arrays have been prepared via a two-step approach comprised with hydrothermal-calcination and electrochemical deposition procedures, successfully. In the beginning, CoMn2O4 nanoneedle arrays took root on Ni foam to form the core skeleton and subsequently, hierarchical Ni3S2 nanosheets uniformly overlaid on the surface of CoMn2O4 nanoneedles shaping the shell structure. This CoMn2O4@Ni3S2 material was measured directly as supercapacitor electrode and presented high specific capacity of 192.2 mAh g−1 with current density of 1 A g−1. Besides, the electrode delivered outstanding cyclical stability as the capacity retention attained 90.2% after charge–discharge measurement at a large current density of 10 A g−1 for 10 000 cycles. Furthermore, a hybrid supercapacitor assembled by CoMn2O4@Ni3S2 cathode and activated carbon anode represented a high energy density of 51.2 Wh kg−1 with the power density of 1030.0 W kg−1. This work shows a facile and inexpensive procedure to design high-performance and strong-stability supercapacitor electrodes.

Construction of multiple electron transfer paths in 1D core-shell hetetrostructures with MXene as interlayer enabling efficient microwave absorption

The exploitation of multicomponent nanocomposites with suitable hierarchical heterostructures is an attractive strategy to obtain high-performance microwave absorption materials. In this work, a versatile strategy is proposed for synthesizing 1D hierarchical core-shell structure with Co-ZIF arrays derived carbon nanotubes (CNTs) coupled on cotton fiber (CF)-supported MXene shell (Co/CNTs-MXene@CF). The advantages of Co-ZIF arrays derived CNTs and MXene dielectric layer can be efficiently integrated to realize multiple electron transfer paths by the construction of the well-designed hierarchical structure. The designed heterogeneous composites consist of the interlayer MXene and CNTs grow sequentially from the outermost Co-ZIF nanosheet arrays with appropriate conductivity and abundant heterointerfaces, which can improve the conduction loss and interfacial polarization response. As expected, the elaborate 1D Co/CNTs-MXene@CF heterostructures exhibit the optimal reflection loss of −61.41 dB at 2.52 mm and effective absorption bandwidth reaches 5.04 GHz with a thickness of only 1.5 mm. The experimental results demonstrate that the optimized structure dramatically improves the electromagnetic wave attenuation behavior. This work illuminates a new design strategy for the preparation of multicomponent composites with reasonable hierarchical structure that enables high-performance microwave absorption materials.