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Due to the enlarged interlayer spacing of anion-inserted hydroxides and their increased surface area, the unique structure of double-layered hydroxides is often beneficial for electrochemical energy storage. This work demonstrates that Ce3+-regulated CoNi-layered double hydroxides (CoNi-LDHs) significantly enhance the kinetics of electron transfer and ion motion with increased layer positive charges and weakened O–H bonds. The Ce3+ addition enabled a high rate capacitance of 1000 F g−1 at an ultrahigh charge rate of 50 A g−1 compared with 1322 F g−1 at 1 A g−1. Served as Lewis acid sites, the substituting trivalent Ce3+ for Co2+ decreases the energy barrier of proton diffusion and promotes the fast charge storage kinetics by increasing the hole carrier concentration (6.74 × 1024 cm−3). The fabricated supercapacitor device achieves a high energy density of 30 W h kg−1 at a power density of 10 kW kg−1 (40 A g−1) based on the total mass of active materials. This work simultaneously enhanced intrinsic electronic conductivity and ion diffusion in an electrode by Ce3+ addition. [ABSTRACT FROM AUTHOR]

Due to yttrium aluminum garnet (YAG) having many excellent properties, investigation of the liquid structure of YAG at high temperatures is significant for numerous fields, including crystal nucleation, glass fabrication, and single-crystal growth. The structure of YAG within a certain temperature range, including the melting point, was studied by molecular dynamic simulations, and a YAG single crystal was rapidly grown. Compared with the YAG crystal, the coordination number of oxygen ions for both Al3+ and Y3+ dropped, and the bond length between the cations and anions shortened after melting. These two phenomena can be understood systematically within the framework of Pauling's third rule, and its universality has been verified in various oxide systems. In the liquid YAG, the coordination number decreased and the bond lengths between cations and anions reduced with the increase in temperature. Furthermore, the motifs in the melt were very different from those in the YAG crystal, and the main structural units in the melt were AlO4 and YO7. Based on the understanding of the structure of the YAG melt, an insight could be gained into the phase selection in the undercooled YAG melt, and a rapid pull-up growth of YAG was realized by using the Czochralski method. [ABSTRACT FROM AUTHOR]

High‐performance rechargeable Zn‐air batteries with long‐life stability are desirable for power applications in electric vehicles. The key component of the Zn‐air batteries is the bifunctional oxygen electrocatalyst, however, designing a bifunctional oxygen electrocatalyst with high intrinsic reversibility and durability is a challenge. Through density functional theory calculations, it is found that the catalytic activity originated from the electronic and geometric coordination structures synergistic effect of the Fe and Co dual‐sites with metal‐N4 coordination environment, assisting the stronger hybridization of electronic orbitals between Co (dxz, dz2) and OO* (px, pz), thus making the stronger O2 active ability of Co active site. These findings enable to development of a fancy dual single‐atom catalyst comprising adjacent FeN4 and CoN4 sites on N‐doped carbon matrix (FeCo‐NC). FeCo‐NC exhibits extraordinary bifunctional activities for oxygen reduction and evolution reaction (ORR/OER), which displays high half‐wave potential (0.893 V) for the ORR, and low overpotential (343 mV) at 10 mA cm−2 for the OER. The assembled FeCo‐NC air‐electrode works well in the flexible solid‐state Zn‐air battery with a high specific capacity of 747.0 mAh g−1, a long‐time stability of more than 400 h (30 °C), and also a superior performance at extreme temperatures (−30 °C–60 °C). [ABSTRACT FROM AUTHOR]

Abstract A size-controlled Zn(OH)2 template is used as a case study to explain the chemical strategy that can be executed to chemically engineering various nanoscale cavities. Zn(OH)2 octahedron with 8 vertices and 14 edges is fabricated via a low temperature solution route. The size can be tuned from 1 to 30 μm by changing the reaction conditions. Two methods can be selected for the hollow process without loss of the original shape of Zn(OH)2 template. Ion-replacement reaction is suitable for fabrication of hollow sulfides based on the solubility difference between Zn(OH)2 and products. Controlled chemical deposition is utilized to coat an oxide layer on the surface of Zn(OH)2 template. The abundant hydroxyl groups on Zn(OH)2 afford strong coordination ability with cations and help to the coating of a shell layer. The rudimental Zn(OH)2 core is eliminated with ammonia solution. In addition, ZnO-based heterostructures possessing better chemical or physical properties can also be prepared via this unique templating process. Room-temperature photoluminescence spectra of the heterostructures and hollow structures are also shown to study their optical properties.

Abstract Single-crystalline V2O5·xH2O nanorings and microloops were chemically assembled via an ion-induced chemical spinning route in the designed hydrothermal system. The morphology and structure of products were investigated by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray powder diffraction (XRD) measurement, energy-dispersive X-ray spectroscopy (EDS) microanalysis and thermal gravimetric analysis (TGA) revealed that the composition of nanorings and microloops is V2O5·1·1H2O. For these oxide nanorings and microloops, the cation-induced coiling growth mechanism of vanadium pentoxide nanobelts has been proposed on the basis of crystallographic structure of vanadium pentoxide. Our proposed chemical spinning process and the rational solution-phase synthesis route can also be extended to prepare novel 1D materials with layered or more complex structures.

Abstract Hollow nanostructured anode materials lie at the heart of research relating to Li-ion batteries, which require high capacity, high rate capability, and high safety. The higher capacity and higher rate capability for hollow nanostructured anode materials than that for the bulk counterparts can be attributed to their higher surface area, shorter path length for Li+ transport, and more freedom for volume change, which can reduce the overpotential and allow better reaction kinetics at the electrode surface. In this article, we review recent research activities on hollow nanostructured anode materials for Li-ion batteries, including carbon materials, metals, metal oxides, and their hybrid materials. The major goal of this review is to highlight some recent progresses in using these hollow nanomaterials as anode materials to develop Li-ion batteries with high capacity, high rate capability, and excellent cycling stability.

Abstract The formation of tubular nanostructures normally requires layered, anisotropic, or pseudo-layered crystal structures, while inorganic compounds typically do not possess such structures, inorganic nanotubes thus have been a hot topic in the past decade. In this article, we review recent research activities on nanotubes fabrication and focus on three novel synthetic strategies for generating nanotubes from inorganic materials that do not have a layered structure. Specifically, thermal oxidation method based on gas–solid reaction to porous CuO nanotubes has been successfully established, semiconductor ZnS and Nb2O5nanotubes have been prepared by employing sacrificial template strategy based on liquid–solid reaction, and an in situ template method has been developed for the preparation of ZnO taper tubes through a chemical etching reaction. We have described the nanotube formation processes and illustrated the detailed key factors during their growth. The proposed mechanisms are presented for nanotube fabrication and the important pioneering studies are discussed on the rational design and fabrication of functional materials with tubular structures. It is the intention of this contribution to provide a brief account of these research activities.

The floating zone technique is a popular method for crystal growth of nonconventional superconductors and magnetic materials. However, the quality must be characterized with particular care with respect to their actual crystallinity since not everything grown by floating zone method is a single crystal. In this paper, the molten‐zone sensitive material LiCoPO4 has been grown by the floating zone method using Co(NO3)2∙6H2O and CoO precursors, respectively, abbreviated as LCPN and LCPO. The grown materials are characterized regarding their chemical composition, phase purity, crystal perfection, and orientation. In order to optimize crystal growth and quantitatively characterize its crystallinity quality, the development factor (V) has been proposed to determine the growth rate of the grains, while the orientation deviation factor (δ) for assessing the quality of the grown crystals. The development factors V for LCPN and LCPO are calculated to be 0.05 and 0.09, respectively, indicating that the grains of LCPO develop faster than those of LCPN. At the same time, the orientation deviation factor of LCPO exceeds that of LCPN (δ(LCPO) = 2.00, δ(LCPN) = 0.77) suggesting a higher quality for the latter. This model provides significant guidance for the evaluation of other materials grown by the floating zone method. [ABSTRACT FROM AUTHOR]