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We developed a solid phase method to fabricate structurally ordered Pt3Co/C nanoparticles (NPs) with controllable component proportion as a high efficiency catalyst toward oxygen-reduction reaction. As a result, Pt3Co/C NPs exhibit high crystallinity with small average size and narrow size distribution. Moreover, the ordered Pt3Co/C NPs own enhanced ORR catalytic performance in acid. During the preparation process, the NaCl-matrix acts synergistically with carbon black as nanoreactors for Pt alloying with Co, avoiding serious sintering resulted by annealing at high temperature. Furthermore, other Pt-based NPs supported on carbon can also be prepared by this methodology.

Ni0.5Zn0.5Fe2−xCrxO4 (0≤x≤0.5) ferrites were successfully prepared by conventional solid state reaction method to investigate the effect of chromium substitution on the structural, electrical and magnetic properties. X-ray powder diffraction results demonstrate that all the prepared samples are well crystallized single-phase spinel structures without secondary phase. As chromium concentration increases, the lattice parameter and crystallite size gradually decrease. The magnetic measurement indicates that saturation magnetization is substantially suppressed by Cr3+ doping, changing from 73.5 A·m2/kg at x=0 to 46.3 A·m2/kg at x=0.5. While the room-temperature electrical resistivity is more than four orders of magnitude enhanced by Cr3+ substitution, reaching up to 1.1×108 Ω·cm at x=0.5. The dielectric constant monotonously decreases with rising frequency for these ferrites, showing a normal dielectric dispersion behavior. The compositional dependence of dielectric constant is inverse with that of electrical resistivity, which originates from the reduced Fe2+/Fe3+ electric dipole number by doping, indicating inherent correlation between polarization and conduction mechanism in ferrite.

Reduced graphene oxide (rGO) has attracted great attention as a promising electrode material for supercapacitors. Herein, polystyrene (PS) colloidal microsphere was used as spacers embedded in the ...

We report a novel Ni3S2 carbon coated (denoted as NCC) rod-like structure prepared by a facile one-pot hydrothermal method and employ it as a binder free electrode in supercapacitor. We coated carbon with glucose as carbon source on the surface of samples and investigated the suitable glucose concentration. The as-obtained NCC rod-like structure demonstrated great performance with a huge specific capacity of 657 C g−1 at 1 A g−1, preeminent rate capability of 87.7% retention, the current density varying to 10 A g−1, and great cycling stability of 76.7% of its original value through 3500 cycles, which is superior to the properties of bare Ni3S2. The result presents a facile, general, viable strategy to constructing a high-performance material for the supercapacitor applications.

A facile two-step method is developed for large-scale synthesis of chemically ordered Pt3Co nanoparticles (NPs) as a high-performance catalyst for hydrogen evolution reaction. Due to the NaCl-matrix as dispersing media avoids the severe aggregation during the high-temperature annealing process, the resulting Pt3Co NPs are pure and well crystallized with narrow size distribution. Furthermore, the chemically ordered Pt3Co NPs exhibit excellent HER property in acidic solution. Our methodology can be also applied to synthesis of other Pt-based NPs.

Herein, a novel preparation route of bimetallic spherical core-shell particles of immiscible metal system was developed and demonstrated through the synthesis of Fe@Cu core–shell microsphere particles. Copper ferrite (CuFe2O4) was used as precursor for the preparation of the Core–shell structured Fe@Cu microsphere using the solid-state immiscibility of Fe and Cu and the low wettability strategy of the liquid-solid interface of graphite at 1403 K. The results showed that phase separation occurred between Cu and Fe, where Cu tended to move towards the surface of the particles and Fe was more concentrated in the center of the particles, due to the lower surface energy of liquid Cu with respect to solid Fe. This was followed by formation of metal droplets located on loose graphite flakes on the spherical Fe@Cu due to the solid-liquid interfacial tension. The as-prepared Fe@Cu microsphere exhibited good spherical shapes and smooth surfaces. The cross-sectional micrographics and element mapping of the spherical particles confirmed the evenly distributions of the Fe-rich core and Cu-rich shell. This strategy is promising for the fabrication of core–shell structured spherical particles for immiscible alloys.

Co3O4 as an electrode material has been widely used for energy storage. However, it has low capacity and is generally associated with poor cycle life and stability. We designed the Co3O4 hollow tube arrays on Ni foam though a facial strategy based on the ZnO sacrificial template method. Benefit from the unique hollow structure advantage and the low resistance brought by the use of self-supporting method without binder. Compared to Co3O4 directly grown on a substrate, the as-prepared hollow Co3O4 structure exhibits large electrochemical capacity of 748.1 C g−1 at 1 A g−1, the result is larger than that of pure Co3O4 directly growing on the substrate without adding Zn2+ as the template. Furthermore, a hybrid supercapacitor device Zn@Co//AC reaches the specific energy of 60.91 Wh kg−1 under the specific power of 450 W kg−1.

Monodisperse spherical Cu-Sn alloy powders were successfully synthesized via the reduction of mixture CuO-SnO2 powders coupled with in-situ de-wetting of liquid-solid interface. The alloy droplets were divided into small units using a graphite sea as solid dispersant to suffer from agglomeration. Fully dense without pores and bulk inclusions, the cross-sectional micrographics of the spherical alloy particles indicate an evenly distribution of the Cu and Sn. The Cu-Sn alloy powders exhibit a good spherical shape and smooth surface, suggesting that the liquid Cu-Sn alloy completely de-wets from the graphite surface. Our strategies are expected to provide a new route for fabrication of high-quality spherical Cu-Sn alloy powders via the reduction of mixture metal oxides.

Here, we present a liquid–solid method (termed “LS method”) for the formation of spherical metal powders. By taking advantage of the low wettability of metal liquids on a solid powder, spherical metal droplets were formed under the influence of interfacial and surface tension, as demonstrated for copper, silver, aluminum, copper–tin alloy, copper–zinc alloy, and amorphous magnetic iron–silicon–boron materials. This LS method is a versatile and universal route and would be applied in powder metallurgy, 3D printing and metal injection modeling. We believe this method provide an additional way for the formation of spherical metal powders. Keywords: Surface energy, Interface wetting, Powder processing

Nitrogen-doped graphene deposited on nickel foam was prepared via a simple hydrothermal process using urea as the reducing agent and nitrogen source and was directly applied as a binder-free supercapacitor electrode. The N content was 5.01 at. %. The electrochemical test of the prepared N-doped graphene showed ideal and reversible capacitive behaviour and excellent electrochemical performance, with a high specific capacitance of 223 F g−1 at 0.29 A g−1, a high-rate capability with the specific capacitances maintained at 184 F g−1 at a high rate of 35.7 A g−1, and good cycling stability with the specific capacitance of the N-doped graphene increased to 206 F g−1 after 3000 cycles. The results suggest its promising application as an electrode material for supercapacitor.

Here, porous grapheme oxide (GO) gel deposited on nickel foam was prepared by using polystyrene (PS) colloidal particles as spacers for use as electrodes in high rate supercapacitors, then reduced by Vitamin C aqueous solution in ambient condition. The PS particles were surrounded by reduced graphene oxide (rGO) sheets, forming crinkles and rough textures. When PS particles were selectively removed, rGO gel coated on the skeleton of Ni foam can formed an open porous structure, which prevents elf-aggregation and restacking of graphene sheets. The porous rGO-based supercapacitors exhibit excellent electrochemical performances such as a specific capacitance of 152 F g−1 at 1 A g−1, high rate capability of 53% capacitance retention upon a current increase to 100 A g−1 and good cycle stability, due to effective rapid and short pathways for ionic and electronic transport provided by the sub-micrometer structure of rGO gel and 3D interconnected network of Ni foam.

Spherical Fe-based magnetic powders were obtained by taking advantage of the surface tension of a molten metal and the de-wetting of metal droplets on a solid graphite sea. The surface carbides inhibit the interfacial reaction and suppress the wetting of the alloy in the graphite substrate. Cross-sectional micrographs of the spherical particles indicate that the particles are fully dense without pores and bulk inclusions. The amorphous degree of the spherical powder was improved by directly quenching in water compared to the raw materials, and the directly quenched sample exhibits excellent soft magnetic properties. Our strategy is expected to provide a new route for the fabrication of spherical insulation coated Fe-based magnetic powders for use in high frequency devices as magnetic core powders.

Here, we demonstrate the design of a binder-free reduced graphene oxide (rGO) and polystyrene colloidal microsphere (PS) compound with rGO/PS/rGO sandwich structure and application for supercapacitors electrode. rGO and PS are alternately deposited into 3D Ni foam by a simple layer-by-layer assembly based on dip-coating. The interlayer space of rGO film expanded by PS microsphere and 3D structure of compound electrode can effectively shorten diffusion pathways of ions and accelerate the transport of ions into graphene sheets. The resulting rGO/PS compound electrode exhibits a high specific capacitance with 164.7[Formula: see text]F g[Formula: see text], and outstanding rate capability. It is found that the specific capacitance is dependent on the number of rGO film layers in rGO/PS compound electrode.

We report a pure ferromagnetic metallic magnetoplasmonic structure consisting of two-dimensional ordered Ni nanodisks array on Co film. With a sufficient height of the nanodisks, a steep and asymmetric Fano resonance can be excited in this structure. We attribute the fascinating spectral lineshape to the strong coupling between the excitation of surface plasmon polaritons at the interface and the localized surface plasmon resonance of nanodisks. The conclusion is fully confirmed by spectrum measurements in nanostructures with different heights. Furthermore, the enhancement and sign of the magneto-optical Kerr rotation in this structure are significantly modified by the Fano resonance.

The properties of optics and magneto-optical Faraday effects in a metal-dielectric tri-layer structure with subwavelength rectangular annular arrays are investigated. It is noteworthy that we obtained the strongly enhanced Faraday rotation of the desired sign along with high transmittance by optimizing the parameters of the nanostructure in the visible spectral ranges. In this system, we obtained two extraordinary optical transmission (EOT) resonant peaks with enhanced Faraday rotations, whose signs are opposite, which may provide the possibility of designing multi-channel magneto-optical devices. Study results show that the maximum of the figure of merit (FOM) of the structure can be obtained between two EOT resonant peaks accompanied by an enhanced Faraday rotation. The positions of the maximum value of the FOM and resonant peaks of transmission along with a large Faraday rotation can be tailored by simply adjusting the geometric parameters of our models. These research findings are of great importance for future applications of magneto-optical devices.