Unique Core-shell Nanostructure Research Articles

C@SnS2 core-shell 0D/2D nanocomposite with excellent electrochemical performance as lithium-ion battery anode

C@SnS2 core-shell 0D/2D nanocomposite was successfully prepared by a one-step hydrothermal method. The SnS2 nanosheets were heterogeneously nucleated and grown on the surface of carbon spheres. As an anode for lithium-ion batteries, the electrochemical performance of the C@SnS2 composite outperforms that of SnS2 nanoflowers. After 100 cycles, the reversible discharge specific capacity reaches an impressive value of 802 mAh g−1 at a current density of 100 mA g−1. Even after 600 cycles, the discharge specific capacity remains a value of 442 mAh g−1, under a high current density of 1 A g−1. This remarkable lithium-ion storage performance can be attributed to the unique core-shell nanostructure and the synergy between SnS2 nanosheets and carbon spheres. This study advances our understanding of the vital role of carbon in fabricating nano-heterojunction or composite electrodes and provides a feasible route to significantly improve the electrochemical properties of SnS2 and other metal sulfides.

Preventing the Galvanic Replacement Reaction toward Unconventional Bimetallic Core-Shell Nanostructures.

A bimetallic core-shell nanostructure is a versatile platform for achieving intriguing optical and catalytic properties. For a long time, this core-shell nanostructure has been limited to ones with noble metal cores. Otherwise, a galvanic replacement reaction easily occurs, leading to hollow nanostructures or completely disintegrated ones. In the past few years, great efforts have been devoted to preventing the galvanic replacement reaction, thus creating an unconventional class of core-shell nanostructures, each containing a less-stable-metal core and a noble metal shell. These new nanostructures have been demonstrated to show unique optical and catalytic properties. In this work, we first briefly summarize the strategies for synthesizing this type of unconventional core-shell nanostructures, such as the delicately designed thermodynamic control and kinetic control methods. Then, we discuss the effects of the core-shell nanostructure on the stabilization of the core nanocrystals and the emerging optical and catalytic properties. The use of the nanostructure for creating hollow/porous nanostructures is also discussed. At the end of this review, we discuss the remaining challenges associated with this unique core-shell nanostructure and provide our perspectives on the future development of the field.

Single‐Source‐Precursor‐Derived Binary FeNi Phosphide Nanoparticles Encapsulated in N, P Co‐Doped Carbon as Electrocatalyst for Hydrogen Evolution Reaction and Oxygen Evolution Reaction

Water‐splitting processes require advanced catalysts for the electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). A facile and cost‐effective approach using single‐source precursors (SSPs) to prepare active and durable bifunctional electrocatalysts consisting of core–shell structured transition metal phosphide (TMPs) nanoparticles dispersed and immobilized in a highly defective N‐, P‐codoped carbon matrix. The bimetallic FeNi phosphide supported on N‐, P‐codoped carbon is synthesized through pyrolysis at 900 °C under an argon atmosphere (FeNiP@NPC‐900), displaying promising electrocatalytic performance for both HER and OER, with low overpotentials of 191 and 278 mV, respectively. Furthermore, FeNiP@NPC‐900 exhibits remarkable durability in both acidic and alkaline electrolytes. The excellent catalytic and long‐term performance is attributed to several factors, including the novel SSP approach, which prevents the agglomeration of active TMPs particles, the in situ formation of exposed nanopores during the carbonization of the precursor without using surfactants, and the heterostructure between highly defective carbon and TMPs, which positively influences the electronic structure at the interface and facilitates charge transfer. The unique core–shell nanostructure protects the catalytically active phase from corrosion and synergistically promotes the activity performance. Therefore, a new strategy for designing active and stable heterostructured TMPs@carbon‐based electrocatalysts is provided.

Single-Source-Precursor Derived Transition Metal Alloys Embedded in Nitrogen-Doped Porous Carbons as Efficient Oxygen Evolution Electrocatalysts.

Carbon supported metallic nanomaterials are of great interest due to their low-cost, high durability and promising functional performance. Herein, a highly active oxygen evolution reaction (OER) electrocatalyst comprised of defective carbon shell encapsulated metal (Fe, Co, Ni) nanoparticles and their alloys supported on in-situ formed N-doped graphene/carbon nanotube hybrid is synthesized from novel single-source-precursors (SSP). The precursors are synthesized by a facile one-pot reaction of tannic acid with polyethylenimine and different metal ions and subsequent pyrolysis of the SSP. Benefiting from the heteroatom doping of carbon and formation of well-encapsulated metal/alloy nanoparticles, the obtained FeNi@NC-900 catalyst possesses lowest overpotentials of 310 mV to achieve a current density of 10 mA cm-2 for OER with a small Tafel slope value of 45 mV dec-1 , indicating excellent catalytic performance due to the following features: (1) A synergistic electronic effect among metal alloy nanoparticles, nitrogen-doped carbon, and entangled carbon nanotubes; (2) penetration of electrolyte is promoted towards the active sites through the porous structure of the formed mesoporous carbon clusters; (3) the unique core-shell nanostructure of the hybrid material effectively curbs the degradation of electrocatalyst by protecting the alloy nanoparticles from harsh electrolyte. This work advances an inexpensive and facile method towards the development of transition metal-based hybrid material for potential energy storage and conversion.

Electrochemical charge/discharge cycling and morphological effects in MnO2/PANC nanostructures for supercapacitors

The improvement of electrochemical properties of MnO2 has been an attractive topic for a long time. Here, MnO2/polyacrylonitrile carbon (MnO2/PANC) nanostructures with well-modified morphology are required by chemical direct synthesis. The cycling stability and specific capacitance performance of MnO2/PANC electrode are enhanced during electrochemical cycling and explored to be closely related to the internal morphologies and crystal form of the various MnO2/PANC nanostructures. The Na+ ion and PANC are forced to interact with increased active sites of the MnO2/PANC surface by cycling protocol. The resulting electrode exhibits the defective nanostructure, in which the MnOC bond is introduced and comprehensive Mn valence occurred in the untrathin MnO2/PANC nanostructure; such unique core-shell nanostructure, providing more structural defects, increased surface area and rich functional groups, and subsequently, enhanced electrochemical capacitance performance. Therefore, this work suggests a new concept for the development of manganese-based electrode materials with enhanced performance and may have broad application in high-energy storage devices.

Core–Shell CuPd@NiPd Nanoparticles: Coupling Lateral Strain with Electronic Interaction toward High-Efficiency Electrocatalysis

Geometric structure and chemical composition are two critical factors that determine the electronic properties of an active metal favorable for a given catalytic reaction. In this scenario, we develop a wet-chemistry method to construct core–shell nanoentities consisting of a CuPd alloy core and a NiPd alloy shell, termed as CuPd@NiPd, which involves the synthesis of CuNi alloy seeds, and a subsequent galvanic replacement reaction with Pd2+ precursors in an organic medium at elevated temperature. In these unique core–shell nanostructures, the compressive lattice strain between core and shell regions and the electronic interaction between Pd and transitional elements could be coupled together to lead to a downshift of the d-band center of Pd sites, thus endowing them with good activity for catalyzing ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR). In particular, at an appropriate Pd/Cu precursor ratio of 1/1, the as-prepared core–shell CuPd@NiPd nanoparticles exhibit a mass activity of 5.1 A mg–1 for EOR and a half-wave potential of 0.91 V for ORR at room temperature in an alkaline medium, outperforming alloy CuPd, NiPd counterparts, commercial Pd/C, and the vast majority of recently reported Pd-based electrocatalysts.

Flexible CuCo2O4@Ni-Co-S hybrids as electrode materials for high-performance energy storage devices

Rational design of electrode meterials with unique core-shell nanostructures is of great significance for improving the electrochemical performance of supercapacitors. In this work, we prepare several CuCo2O4@Ni-Co-S composite electrodes by a controllable hydrothermal and electrodeposition route. One-dimensional nanowires can shorten the ions transport path, while two-dimensional nanosheets expose many active sites. This enables three-dimensional structured composite with high electrochemical activity. The as-prepared heterostructured materials show a specific of 1048 C/g at 1 A/g. It still maintains 75.6% of initial capacity after 20000 cycles at 10 A/g. The device delivers an energy density of 79.2 Wh/kg when the power density reaches to 2280 W/kg. Moreover, it possesses an excellent mechanical stability after repeated folding at different angles

Carbon encapsulated bimetallic FeCo nanoalloys for one-step hydroxylation of benzene to phenol

Carbon encapsulated iron catalysts hold great potential for one-step hydroxylation of benzene to phenol due to their unique core-shell nanostructures. However, their catalytic performance is moderate, since the carbon shells have impeded their activity toward H2O2 activation. Herein, we demonstrate that alloying engineering of Fe cores with Co atoms is a promising strategy to address the issue about H2O2 activation. The incorporation of Co into Fe cores can generate strong synergetic effects to promote H2O2 activation, while still maintaining the structural benefits of carbon shells for benzene hydroxylation reaction. As a result, the phenol yield obtained on carbon encapsulated FeCo (FeCo@C) reaches to 26.4 ± 0.7% with a selectivity of 96.2 ± 1.2%, much higher than that of Fe@C and Co@C. With the improved intrinsic catalytic behavior toward H2O2 activation and well-reserved carbon structure benefits, FeCo@C should be a promising catalyst for a broad liquid-phase reactions using H2O2 as the oxidant.

Upconverting Er3+-Yb3+ Inorganic/Covalent Organic Framework Core-Shell Nanoplatforms for Simultaneous Catalysis and Nanothermometry.

Lanthanide-based luminescent nanoparticles that are thermally responsive can be used to probe temperature changes at a nanoscale regime. However, materials that can work as both a nanothermometer and a catalyst are limited. Herein, we show that covalent organic frameworks (COFs), which is an emerging class of porous crystalline materials, can be grown around lanthanide nanoparticles to create unique core-shell nanostructures. In this way, the COF (shell) supports copper metal ions as catalytic sites and simultaneously lanthanide nanoparticles (β-NaLuF4:Gd,Er,Yb-core) locally measure the temperature during the catalytic reaction. Moreover, β-NaLuF4:Gd,Er,Yb nanoparticles are upconverting materials and hence can be excited at longer wavelengths (975 nm), which do not affect the catalysis substrates or the COF. As a proof-of-principle, a three-component addition reaction of benzaldehyde, indole, and malononitrile was studied. The local temperature was probed using luminescence nanothermometry during the catalytic reaction.

S, N co-doped carbon nanotube encased Co NPs as efficient bifunctional oxygen electrocatalysts for zinc-air batteries

For the practical application of metal-air batteries, developing high-active and low-cost bifunctional oxygen reduction reaction (ORR) and oxygen evolution reduction (OER) catalysts is crucial and challenging. This study designed a unique ordered three-dimensional (3D) core–shell nanostructure bifunctional ORR and OER electrocatalysts consisting of Co nanoparticles (NPs) embedded in S, N co-doped carbon nanotubes (S,N-Co@CNT). The prepared S,N-Co@CNT exhibited excellent bifunctional electrocatalytic performance, with a high half-wave potential of 0.874 V versus reversible hydrogen electrode (RHE) toward ORR, and a low overpotential of 276 mV at 10 mA·cm−2 for the OER. The unique core–shell nanostructure has delivered considerable durability and stability in the S,N-Co@CNT, demonstrating almost no change in the potential gap between the ORR and OER after more than 5000 cycles of the accelerated durability test. Moreover, the S,N-Co@CNT serves as a high-active and low-price air–cathode catalyst for a rechargeable zinc-air battery, with a high peak power density of 171 mW·cm−2, and a long continuous charging-discharging ability. Based on mechanistic studies, the high activity of the S,N-Co@CNT was derived from the suitable oxygen adsorption energy due to the effects from S, N co-doping. The outcomes from this study offer a novel strategy to prepare non-noble metal bifunctional oxygen catalysts for metal-air batteries.

Polysaccharide Nanocapsules for Drug Delivery Applications, Current Status and Future Perspectives

In recent years pharmaceutical formulations using polymeric nanocapsules have been widely studied for developing novel drug delivery strategies. Nanocapsules provide a unique core-shell nanostructure, consisting of a liquid/solid core surrounded by a polymeric shell. Natural or modified polysaccharides are prime candidates for use as building blocks of the nanocapsule shells, due to their demonstrated safety, versatility and low cost and to the fact that they are widely used as excipients in classical drug formulations. The aim of this paper is to present the recent advances in drug delivery strategies using polysaccharidic nanocapsules and to discuss future opportunities and challenges in developing modern pharmaceutical formulations using such systems.

Construction of dual metal ferrite-based core-shell nanostructures as low-cost multimetal electrode for boosting energy density of flexible asymmetric supercapattery

We report the synthesis and fabrication of economically cheaper and binder-free hierarchical core-shell nanostructures of copper ferrite nanorods and nickel ferrite nanosheets (CuFe2O4–NR@NiFe2O4–NS) via a two-step wet chemical technique. The unique core-shell (nanorods@nanosheets) nanostructures offer multiple redox couples (Cu2+, Fe3+, and Ni2+), smaller ion diffusion path, and faster electron movement. When evaluated as an individual electrode in aqueous potassium hydroxide solution, the as-synthesized CuFe2O4–NR@NiFe2O4–NS electrode demonstrate superior electrochemical behaviour with concurrent specific capacity of 1366 C g−1 at current rate 1 A g−1, and 94% capacity retention over 10,000 cycles. A flexible asymmetric supercapattery device is assembled comprising positive electrode of CuFe2O4–NR@NiFe2O4–NS and negative electrode of reduced graphene oxide (rGO) with PVA-KOH semisolid electrolyte. The ASC cell manifest enhanced specific energy of 72 Wh kg−1, specific power of 0.287 kW kg−1 and outstanding cycle life (~97% of retention over 10,000 cycles at 10 A g−1). The superior specific capacity, capacity retention, and excellent cyclic life endow such multimetal ferrite-based core-shell architecture with tremendous potential for use as electrode materials for fabricating next generation energy storage devices.

High performance flexible energy storage device based on copper foam supported NiMoO4 nanosheets-CNTs-CuO nanowires composites with core–shell holey nanostructure

Because of the intensified electrochemical activities, mixed metal oxides as a representative for pseudocapacitive materials play a key role for high performance supercapacitor electrodes. Nevertheless, low ion and electron transfer rate and poor cycling performance in the electrode practically restrict further promotion of their electrochemical performance. In order to offset the defect, a novel copper (Cu) foam-supported nickel molybdate nanosheet decorated carbon nanotube wrapped copper oxide nanowire array (NiMoO4 NSs-CNTs-CuO NWAs/Cu foam) flexible electrode is constructed. The as-prepared electrode demonstrates a unique core-shell holey nanostructure with a large active surface area, which can provide a large number of active sites for redox reactions. Besides, the CNTs networks supply improved conductivity, which can hasten electron transport. Through this simple and efficient design method, the spatial distribution of each component in the flexible electrode is more orderly, short and fast electron transport path with low intrinsic resistance. As a result, the NiMoO4 NSs-CNTs-CuO NWAs/Cu foam as an adhesiveless supercapacitor electrode material exhibits excellent energy storage performance with high specific areal capacitance of 23.40 F cm−2 at a current density of 2 mA cm−2, which outperforms most of the flexible electrodes reported recently. The assembled asymmetric supercapacitor demonstrates an energy density up to 96.40 mW h cm-3 and a power density up to 0.4 W cm-3 under a working voltage window of 1.7 V. In addition, outstanding flexibility of up to 100° bend and good cycling stability with the capacitance retention of 82.53 % after 10,000 cycles can be obtained.

Selective Hydroxylation of Benzene to Phenol over Fe Nanoparticles Encapsulated within N-Doped Carbon Shells

Iron-containing heterogeneous catalysts hold great promising for the direct hydroxylation of benzene to phenol. However, their catalytic performance is greatly hampered by the inherent drawbacks of iron-containing solids, in particular their hydrophilic surface structure and inevitable leaching of iron species during the Fenton process, which result in poor selectivity and durability toward phenol production. Herein, we demonstrate that the encapsulation of iron nanoparticles with N-doped carbon layer as core–shell nanostructures (Fe@NC) is a promising synthetic strategy to advance iron-containing solids for benzene hydroxylation. The rigid carbon shells conformably coating on iron cores not only protect iron from leaching but also facilitate the selective adsorption of benzene molecules on Fe@NC because of their excellent stability against acid etching and hydrophobic surface with the unique π-conjugated electron system. As a result, Fe@NC exhibit a robust catalytic durability and good yield with high selectivity for the direct hydroxylation of benzene to phenol. Benefiting from their unique core–shell nanostructures and strong host–guest electron interaction between metals and carbons, Fe@NC are expected to be promising also for other liquid-phase organic synthesis.

Engineering of oxygen vacancies regulated core-shell N-doped carbon@NiFe2O4 nanospheres: A superior bifunctional electrocatalyst for boosting the kinetics of oxygen and hydrogen evaluation reactions

Exploration of low-cost, highly-efficient, robust electrocatalysts is highly necessary to minimize the cell potential of overall water splitting and encourage the practicality of related energy systems. Oxygen deficient (OV) metal oxides stand out as one of the efficient interfaces for water oxidation, nevertheless, the influence of volume of OV on their electrocatalytic efficiency has not been described yet. To resolve this issue, we establish a facile and low-temperature protocol for the fabrication of core-shell N-carbon@NiFe2O4 nanospheres (NC@NFO) with precisely controlled OV to boost the kinetics of OER and HER. Here, dopamine was used to introduce the N-doped carbon and OV defects in the NFO simultaneously. Furthermore, the ratio of OV can be tuned by the simply varying the reaction time, thus the number of active spots and the catalytic performance has been tuned. By virtue of its unique core-shell nanostructure, larger specific surface area, abundant oxygen vacancies, and excellent synergistic effect of N-carbon and NFO, the NC@NFO-OV-rich achieved current density of 100 mA/cm2 at a very low overpotential of 230 and 200 mV for OER (Tafel slope 42 mV/dec) and HER (Tafel slope 59.6 mV/dec), respectively, superior than most stated noble/non-noble metal-based catalysts. Also, NC@NFO-OV-rich exhibited an exceptional overall water splitting performance with low driving voltage of ≥ 1.45 V, current density of 10 mA cm−2 has achieved at a very low cell voltage of 1.47 V in 1 M KOH with insignificant activity deterioration over 12 h, which is among topmost activities described. Present work not only provides a novel and facile technique to construct N-doped carbon decorated metal oxides with abundant OV but also discovers their prospects as dual-functional electrocatalyst toward overall water splitting.

Construction of hierarchical core-shell ZnCo2O4@Ni-Co-S nanosheets with a microsphere structure on nickel foam for high-performance asymmetric supercapacitors

The hierarchical core-shell ZnCo2O4@Ni-Co-S nanosheets with microsphere structures for supercapacitors were prepared through a facile three-step method including hydrothermal reaction, subsequent annealing and electrodeposition process. The influences of deposition cycles on its structure and electrochemical performances were studied in detail. On account of a synergistic effect of the ZnCo2O4 and Ni-Co-S composite and its unique core-shell nanostructure, the as-prepared electrode reveals excellent supercapacitor properties. The ZnCo2O4@Ni-Co-S with 6 electrodeposition cycles (ZCO@NCS-6) shows high specific capacitance values of 1762.6 F g−1 at 1 A g−1, outstanding rate performance with 81.3% at 50 A g−1, and remarkable long-term stability of 18.6% capacity loss through 5000 cycles. Moreover, the asymmetric supercapacitor (ASC) device was further constructed by using of ZCO@NCS-6 and active carbon to evaluate the practical values of the fabricated composite materials. The assembled ASC device shows the maximum voltage window up to 1.7 V, high energy density of 37.1 W h kg−1 and the excellent cycling life-span (only 9.71% capacitance loss after 8000 cycles). All these results suggest that ZnCo2O4@Ni-Co-S could be the hopeful electrode materials for energy storage devices.

Surface plasma-etching treatment of cobalt nanoparticles-embedded honeysuckle-like nitrogen-doped carbon nanotubes to produce high-performance catalysts for rechargeable zinc-air batteries

Developing high-performance and low-cost catalysts for oxygen reduction reaction (ORR) in metal-air batteries is challenging but necessary for their practical applications and commercialization. In this paper, a core-shell cobalt nanoparticles-embedded honeysuckle-like N-doped carbon nanotube (Co@NCNT) catalyst is synthesized through programmed carbonization with the plasma etching. The Co@NCNT displays a uniform core-shell honeysuckle-like nanostructure and exhibits comparable ORR performance to the commercial 20% Pt/C. The onset potential (Eonset) and half-wave potential (E1/2) of the Co@NCNT is 1.030 V and 0.872 V (vs. RHE), and the potential decay in E1/2 is only 9 mV after 5000 cycles accelerated durability test (ADT). Moreover, a Zinc-air battery (ZAB) with Co@NCNT cathode catalyst exhibits a peak power density of 162.5 mW cm−2 and high rate capability as well as excellent durability. The excellent performance of the Co@NCNT is mainly attributed to the synergistic effect of unique core-shell nanostructure, more defects and active sites as well as more tiny rifts in the carbon-shell induced by the plasma etching.

Facile Route to Achieve Co@Mo2C Encapsulated by N-Doped Carbon as Efficient Electrocatalyst for Overall Water Splitting in Alkaline Media

The development of inexpensive, highly efficient and stable noble metal-free heterostructure bifunctional electrocatalysts is crucial for water electrolysis. Herein, a facile strategy is utilized by pyrolyzing the mixture containing ammonium molybdate tetrahydrate and zeolitic imidazolate framework-67 to achieve a product with Co nanoparticles as core and β-Mo2C embedded in N-doped carbon as a shell (Co@β-Mo2C-NC). The Co@β-Mo2C-NC-0.115 (quantity of Mo precursor) composite illustrates an overpotential (η10) of 188 and 330 mV for hydrogen and oxygen evolution reactions, respectively, and a cell voltage of 1.72 V is required for overall water splitting to attain a current density of 10 mA cm−2 in alkaline media. Remarkably, the Co@β-Mo2C-NC-0.115 catalyst exhibits excellent stability for continuous operation of 15 h chronopotentiometry and 25 h chronoamperometry measurements. The satisfactory electrocatalytic performance can be ascribed to the unique core–shell nanostructure, especially the synergistic effect between Co, β-Mo2C and N-doped carbon. These research findings speculate a straightforward strategy to fabricate MOF derived heterostructures with robust catalytic performance and wide applications in electrocatalysis.

Facile synthesis of Ternary Au@PdNi core-shell nanoparticles with enhanced electrocatalytic performance for ethanol oxidation reaction

We report a facile synthesis of ternary Au@PdNi core-shell nanoparticles (C-SNPs). Au NPs with 15 nm in diameter served as seeds, Pd2+ and Ni2+ were co-reduced on the surface of Au NPs to obtain C-SNPs. These C-SNPs exhibited outstanding catalytic performance (5891 mA mgPd−1) and stability for ethanol oxidation reaction (EOR). The activity was 9.48 times higher than the commercial Pd/C (20% wt). The catalytic mechanism was investigated, and the enhanced catalytic performance of Au@PdNi C-SNPs was mainly attributed to electronic effects between Pd and Au/Ni, and the unique core-shell nanostructure. The present work provides a strategy for rational design of ternary metallic core-shell nanocatalysts, which can achieve high catalytic activity and durability.

Superior uniform carbon nanofibers@g-C3N4 core-shell nanostructures embedded by Au nanoparticles for high-efficiency photocatalyst

Ultrathin g-C3N4 nanolayers were uniformly assembled on Au nanoparticles (NPs) decorated carbon nanofiber (CNFs) by a facile gas-solid approach. The mean thickness of g-C3N4 shell layers on CNFs-Au supports was about 22.5 nm. The ternary system of as-prepared photocatalysts with superior uniformly core-shell nanostructures present enhanced photocatalytic properties. The rate constants (rhodamine B and K2Cr2O7) of CNFs-Au@g-C3N4 were about 3.5 and 4.5 times of g-C3N4 powders, respectively. While the rate of H2-evolution was 2.3-fold of the physical mixture, when the loading amount of Au NPs was about 0.52 At.%. Their excellent photocatalytic activities were attributed to the advantages of their unique core-shell nanostructures and the synergy of the Au NPs as a high-efficiency electron conduction bridge and their surface plasmon resonance (SPR) effect. Moreover, the ternary systems of CNFs-Au@g-C3N4 present the gratifying cycling stability in photocatalytic reactions due to their ultra-long core-shell nanostructures. Our work provides a novel route for designing and constructing multicomponent photocatalyst in wastewater treatment and solar energy applications.