Hierarchical NiCo@NiOOH@CoMoO4 Core–Shell Heterostructure on Carbon Cloth for High-Performance Asymmetric Supercapacitors

The fabrication of low-cost, effective, and highly integrated nanostructured materials through simple and reproducible methods for high-energy-density supercapacitors is highly desirable. Herein, an activated carbon cloth (ACC) is designed as the functional scaffold for supercapacitors and treated hydrothermally to deposit NiCo nanoneedles working as internal core, followed by a dip-dry coating of NiOOH nanoflakes core–shell and uniform hydrothermal deposition of CoMoO₄ nanosheets serving as an external shell. The structured core–shell heterostructure ACC@NiCo@NiOOH@CoMoO₄ electrode resulted in exceptional specific areal capacitance of 2920 mF cm⁻² and exceptional cycling stability for 10 000 cycles. Moreover, the fabricated electrode is developed into an asymmetric supercapacitor which demonstrates excellent areal capacitance, energy density, and power density within the broad potential window of 1.7 V with a cycling life of 92.4% after 10 000 charge–discharge cycles, which reflects excellent cycle life. The distinctive core–shell structure, highly conductive substrate, and synergetic effect of coated material results in more electrochemical active sites and flanges for effective electrons and ion transportation. This unique technique provides a new perspective for cost-efficient supercapacitor applications.     

Synthesis of Palladium-Based Crystalline@Amorphous Core–Shell Nanoplates for Highly Efficient Ethanol Oxidation

Phase engineering of nanomaterials (PEN) offers a promising route to rationally tune the physicochemical properties of nanomaterials and further enhance their performance in various applications. However, it remains a great challenge to construct well-defined crystalline@amorphous core–shell heterostructured nanomaterials with the same chemical components. Herein, the synthesis of binary (Pd-P) crystalline@amorphous heterostructured nanoplates using Cu_3−χP nanoplates as templates, via cation exchange, is reported. The obtained nanoplate possesses a crystalline core and an amorphous shell with the same elemental components, referred to as c-Pd-P@a-Pd-P. Moreover, the obtained c-Pd-P@a-Pd-P nanoplates can serve as templates to be further alloyed with Ni, forming ternary (Pd-Ni-P) crystalline@amorphous heterostructured nanoplates, referred to as c-Pd-Ni-P@a-Pd-Ni-P. The atomic content of Ni in the c-Pd-Ni-P@a-Pd-Ni-P nanoplates can be tuned in the range from 9.47 to 38.61 at%. When used as a catalyst, the c-Pd-Ni-P@a-Pd-Ni-P nanoplates with 9.47 at% Ni exhibit excellent electrocatalytic activity toward ethanol oxidation, showing a high mass current density up to 3.05 A mg_Pd⁻¹, which is 4.5 times that of the commercial Pd/C catalyst (0.68 A mg_Pd⁻¹).     

Core–Shell Tandem Catalysis Coupled with Interface Engineering For High-Performance Room-Temperature Na–S Batteries

The sluggish redox kinetics and shuttle effect seriously impede the large application of room-temperature sodium–sulfur (RT Na–S) batteries. Designing effective catalysts into cathode material is a promising approach to overcome the above issues. However, considering the multistep and multiphase transformations of sulfur redox process, it is impractical to achieve the effective catalysis of the entire S₈→Na₂S_x→Na₂S conversion through applying a single catalyst. Herein, this work fabricates a nitrogen-doped core–shell carbon nanosphere integrated with two different catalysts (ZnS-NC@Ni-N₄), where isolated Ni–N₄ sites and ZnS nanocrystals are distributed in the shell and core, respectively. ZnS nanocrystals ensure the rapid reduction of S₈ into Na₂S_x (4 < x ≤ 8), while Ni–N₄ sites realize the efficient conversion of Na₂S_x into Na₂S, bridged by the diffusion of Na₂S_x from the core to shell. Besides, Ni–N₄ sites on the shell can also induce an inorganic-rich cathode–electrolyte interface (CEI) on ZnS-NC@Ni-N₄ to further inhibit the shuttle effect. As a result, ZnS-NC@Ni-N₄/S cathode exhibits an excellent rate-performance (650 mAh g⁻¹ at 5 A g⁻¹) and ultralong cycling stability for 2000 cycles with a low capacity-decay rate of 0.011% per cycle. This work will guide the rational design of multicatalysts for high-performance RT Na–S batteries.     

Core–Shell Structure and Luminescence of SrMoO_4:Eu~(3+)(10%) Phosphors

SrMoO_4:Eu~(3+)(10%) phosphors were produced via hydrothermal synthesis and co-precipitation.We systematically analyzed how the morphology and luminescence properties of the phosphors were affected by the synthesis conditions,including the p H of the precursor solution,stirring speed,and postsintering temperature.The samples synthesized at p H = 8 and 9 were spindle-like rods with a core–shell structure.When the stirring speed increased to Vs = 150 r/min,the core–shell structure disappeared.Photoluminescence measurements indicated that the Sr Mo O4:Eu3+samples under ultraviolet radiation produced strong red emission centered at 616 nm.The luminescence properties were greatly affected by the p H,stirring during hydrothermal reaction,and use of post-annealing.The related mechansim is discussed.     

Shedding Light on the Role of Misfit Strain in Controlling Core–Shell Nanocrystals

Heteroepitaxial modification of nanomaterials has become a powerful means to create novel functionalities for various applications. One of the most elementary factors in heteroepitaxial nanostructures is the misfit strain arising from mismatched lattices of the constituent parts. Misfit strain not only dictates epitaxy kinetics for diversifying nanocrystal morphologies but also provides rational control over materials properties. In recent years, advances in chemical synthesis along with the rapid development of electron microscopy and X-ray diffraction techniques have enabled a substantial understanding of strain-related processes, which offers theoretical foundation and experimental guidance for researchers to refine heteroepitaxial nanostructures and their properties. Herein, recent investigations on heterogeneous core–shell nanocrystals containing misfit strains are summarized, with a focus on the mechanistic understanding of strain and strain-induced effects such as tuning the epitaxial habit, modulating the optical emission, and enhancing the catalytic activity and magnetic coercivity.     

Study of Structural and Magnetic Properties of Superparamagnetic Fe3O4–ZnO Core–Shell Nanoparticles

In this work, Fe₃O₄–ZnO core–shell nanoparticles have been successfully synthesized using a simple two-step co-precipitation method. In this regard, Fe₃O₄ (magnetite) and ZnO (zincite) nanoparticles (NPs) were synthesized separately. Then, the surface of the Fe₃O₄ NPs was modified with trisodium citrate in order to improve the attachment of ZnO NPs to the surface of Fe₃O₄ NPs. Afterwards, the modified magnetite NPs were coated with ZnO NPs. Moreover, the influence of the core to shell molar ratio on the structural and magnetic properties of the core–shell NPs has been investigated. The prepared nanoparticles have been characterized utilizing transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and vibrating sample magnetometer (VSM). The results of XRD indicate that Fe₃O₄ NPs with inverse spinel phase were formed. The results of VSM imply that the Fe₃O₄–ZnO core–shell NPs are superparamagnetic. The saturation magnetization of prepared Fe₃O₄ NPs is 54.24 emu/g and it decreases intensively down to 29.88, 10.51 and 5.75 emu/g, after ZnO coating with various ratios of core to shell as 1:1, 1:10 and 1:20, respectively. This reduction is attributed to core–shell interface effects and shielding. TEM images and XRD results imply that ZnO-coated magnetite NPs are formed. According to the TEM images, the estimated average size for most of core–shell NPs is about 12 nm.     

Gradient-Concentration Design of Stable Core–Shell Nanostructure for Acidic Oxygen Reduction Electrocatalysis

Manipulating the surface structure of electrocatalysts at the atomic level is of primary importance to simultaneously achieve the activity and stability dual-criteria in oxygen reduction reaction (ORR) for proton exchange membrane fuel cells. Here, a durable acidic ORR electrocatalyst with the “defective-armored” structure of Pt shell and Pt–Ni core nanoparticle decorated on graphene (Pt–Ni@Pt_D/G) using a facile and controllable galvanic replacement reaction to generate gradient distribution of Pt–Ni composition from surface to interior, followed by a partial dealloying approach, leaching the minor nickel atoms on the surface to generate defective Pt skeleton shell, is reported. The Pt–Ni@Pt_D/G catalyst shows impressive performance for ORR in acidic (0.1 m HClO₄) electrolyte, with a high mass activity of threefold higher than that of Pt/C catalyst owing to the tuned electronic structure of locally concave Pt surface sites through synergetic contributions of Pt–Ni core and defective Pt shell. More importantly, the electrochemically active surface areas still retain 96% after 20 000 potential cycles, attributing to the Pt atomic shell acting as the protective “armor” to prevent interior Ni atoms from further dissolution during the long-term operation.     

Mössbauer Studies of the Structure of Core/Shell Fe3O4/γ-Fe2O3 Nanoparticles

Technical Physics Letters - The phase composition, the structure of cores and shells, and the dependences of the shell thickness on the fabrication technique were determined by Mössbauer...     

Activated FeS2@NiS2 Core–Shell Structure Boosting Cascade Reaction for Superior Electrocatalytic Oxygen Evolution

Unlike single-step reactions, multi-step reactions can be greatly facilitated only if all the intermediate reactions can be catalyzed simultaneously and progressively. Herein, the theoretical analysis and experiments to illustrate the superiority of the cascade oxygen evolution reaction (OER) are conducted. As different OER intermediate reactions demand Fe_xNi_1-xOOH with altered Fe/Ni ratios, gradient Fe-doped NiOOH can be an ideal electrocatalyst for the efficient cascade OER in line. Fine controlling of the nucleation sequence of iron and nickel sulfides leads to a FeS₂@NiS₂ core–shell structure. The activated outward diffusion of Fe dopants results in the gradient Fe/Ni ratios in the Fe_xNi_1-xOOH shell, where a cascade OER can happen. Electrochemical tests suggest that the FeS₂@NiS₂ only needs an overpotential of 237 mV to reach the current density of 10 mA cm⁻², with fast reaction kinetics and good stability.     

3D Printing of Viscoelastic Suspensions via Digital Light Synthesis for Tough Nanoparticle–Elastomer Composites

The rheological parameters required to print viscoelastic nanoparticle suspensions toward tough elastomers via Digital Light Synthesis (DLS) (an inverted projection stereolithography system) are reported. With a model material of functionalized silica nanoparticles suspended in a poly(dimethylsiloxane) matrix, the rheological-parameters-guided DLS can print structures seven times tougher than those formed from the neat polymers. The large yield stress and high viscosity associated with these high concentration nanoparticle suspensions, however, may prevent pressure-driven flow, a mechanism essential to stereolithography-based printing. Thus, to better predict and evaluate the printability of high concentration nanoparticle suspensions, the boundary of rheological properties compatible with DLS is defined using a non-dimensional Peclet number (Pe). Based on the proposed analysis of rheological parameters, the border of printability at standard temperature and pressure (STP) is established by resin with a silica nanoparticle mass fraction (ϕ_silica) of 0.15. Above this concentration, nanoparticle suspensions have Pe > 1 and are not printable. Beyond STP, the printability can be further extended to ϕ_silica = 0.20 via a heating module with lower shear rate to reduce the Pe < 1. The printed rubber possesses even higher toughness (Γ ≈ 155 kJ m⁻³), which is 40% higher over that of ϕ_silica = 0.15.     

Development of a Model for the Formation of Materials with a Hierarchical Pore Structure Produced under Sol–Gel Processing Conditions

We have developed a model for the formation of silica-containing synthetic functional materials with a hierarchical pore structure and a large specific surface area under self-assembly conditions of sol–gel processes. The model includes the formation of a three-dimensional core (of a cristobalite type) of sol particles consisting of joined polymorphoids in the form of n-membered rings and a continuous transition between fractal aggregate growth mechanisms, from diffusion-limited to cluster–cluster aggregation, followed by evolution culminating in spinodal decomposition. Hierarchical structures have been studied using three-dimensional simulation with Autodesk 3ds Max software.     

Nanocrystalline Si3N4 with Si–C–N shell structure

Nanocrystalline Si₃N₄ with an amorphous Si–C–N shell structure was synthesized by mechanically activating Si₃N₄ and graphite powder in argon atmosphere at room temperature. Twenty hours of mechanical activation resulted in occurrence of CN bond, which can be identified using Fourier transform infrared spectrometry (FT-IR). When the mechanical activation period was extended to 67 h and then to 90 h, the CN bond was further established. The formation of CN bond under the mechanical activation for 90 h was further confirmed using X-ray photoelectron spectroscopy (XPS). The thickness of Si–C–N shell is 5–7 nm as observed using high-resolution transmission electron microscope.     

Microwave-Assisted Rapid Substitution of Ti for Zr to Produce Bimetallic (Zr/Ti)UiO-66-NH2 with Congenetic “Shell–Core” Structure for Enhancing Photocatalytic Removal of Nitric Oxide

Efficient nitric oxide (NO) removal without nitrogen dioxide (NO₂) emission is desired for the control of air pollution. Herein, a series of (Zr/Ti)UiO-66-NH₂ with congenetic shell–core structure, denoted as Ti-UION, are rapidly synthesized by microwave-assisted post-synthetic modification for NO removal. The optimal Ti-UION (i.e., 2.5Ti-UION) exhibits the highest activity of 80.74% without NO₂ emission with moisture, which is 21.65% greater than that of the UiO-66-NH₂. The NO removal efficiency of 2.5Ti-UION further increases to 95.92% without photocatalyst deactivation under an anhydrous condition. This is because selectively produced NO₂ in photocatalysis is completely adsorbed into micropores, refreshing active sites for subsequent reaction. In addition, the enhanced photocatalytic activity after Ti substitution is due to the presence of Ti electron acceptor, the potential difference between the shell and core of Ti-UION crystal, and the high conductivity of Ti O units. Additionally, the improved adsorption of gas molecules not only favors NO oxidation, but also avoids the emission of NO₂. This work provides a feasible strategy for rapid metal substitution in metal-organic frameworks and insights into enhanced NO photodegradation.     

Metal-free π-conjugated hybrid g-C3N4 with tunable band structure for enhanced visible-light photocatalytic H2 production

Development of low-cost and efficient photocatalytic materials with visible-light response is of urgent need for solving energy and environmental problems.Here,a metal-free two-dimensional (2D) π-conjugated hybrid g-C3N4 photocatalyst with tunable band structure was prepared by a novel one-pot bottom-up method based on a supersaturated precipitation process of urea and triethanolamine (TEOA)solution.The microstructure of the hybrid g-C3N4 is revealed to be a compound of periodic tri-s-triazine units grafted with N-doped graphene (GR) fragments.From experimental evidence and theoretical calcu-lations,the two different π-conjugated fragments in the hybrid g-C3N4 material are proved to construct a 2D in-plane junction structure,thereby expanding the light absorption range and accelerating the inter-face charge transfer.The π-conjugated electron coupling in the 2D photocatalyst eliminates the grain boundary effect,and the coupled highest occupied molecular orbital (HOMO) effectively promotes the separation of photo-induced charge carriers.Compared with the g-C3N4 prepared by the conventional method,the visible-light H2 production activity of the optimized sample is enhanced by 253 ％.This work provides a new strategy of constructing metal-free g-C3N4 hybrids for efficient photocatalytic water splitting.     

Hierarchical and Orderly Surface Conductive Networks in Yolk–Shell Fe3O4@C@Co/N-Doped C Microspheres for Enhanced Microwave Absorption

Constructing the adjustable surface conductive networks is an innovation that can achieve a balance between enhanced attenuation and impedance mismatch according to the microwave absorption mechanism. However, the traditional design strategies remain significant challenges in terms of rational selection and controlled growth of conductive components. Herein, a hierarchical construction strategy and quantitative construction technique are employed to introduce conductive metal–organic frameworks (MOFs) derivatives in the classic yolk–shell structure composed of electromagnetic components and the cavity for remarkable optimized performance. Specifically, the surface conductive networks obtained by carbonized ZIF-67 quantitative construction, together with the Fe₃O₄ magnetic core and dielectric carbon layer linked by the cavity, achieve the cooperative enhancement of impedance matching optimization and synergistic attenuation in the Fe₃O₄@C@Co/N-Doped C (FCCNC) absorber. This interesting design is further verified by experimental results and simulation calculations. The products FCCNC-2 yield a distinguished minimum reflection loss of −66.39 dB and an exceptional effective absorption bandwidth of 6.49 GHz, indicating that moderate conduction excited via hierarchical and quantitative design can maximize the absorption capability. Furthermore, the proposed versatile methodology of surface assembly paves a new avenue to maximize beneficial conduction effect and manipulate microwave attenuation in MOFs derivatives.