Cost-effective electrocatalysts based on nonprecious metals for efficient water splitting are crucial for various technological applications represented by fuel cell. Here, 3d transition metal layered double hydroxides (LDHs) with varied contents of Ni and Fe were successfully synthesized through a homogeneous precipitation. The exfoliated Ni-Fe LDH nanosheets were heteroassembled with graphene oxide (GO) as well as reduced graphene oxide (rGO) into superlattice-like hybrids, in which two kinds of oppositely charged nanosheets are stacked face-to-face in alternating sequence. Heterostructured composites of Ni2/3Fe1/3 LDH nanosheets and GO (Ni2/3Fe1/3-GO) exhibited an excellent oxygen evolution reaction (OER) efficiency with a small overpotential of about 0.23 V and Tafel slope of 42 mV/decade. The activity was further improved via the combination of Ni2/3Fe1/3 LDH nanosheets with more conductive rGO (Ni2/3Fe1/3-rGO) to achieve an overpotential as low as 0.21 V and Tafel plot of 40 mV/decade. The catalytic activity was enhanced with an increased Fe content in the bimetallic Ni-Fe system. Moreover, the composite catalysts were found to be effective for hydrogen evolution reaction. An electrolyzer cell powered by a single AA battery of 1.5 V was demonstrated by using the bifunctional catalysts.

While α-MnO2 has been intensively studied for zinc batteries, δ-MnO2 is usually believed to be more suitable for ion storage with its layered structure. Unfortunately, the extraordinary Zn ion storage performance that δ-MnO2 should exhibit has not yet been achieved due to the frustrating structural degradation during charge–discharge cycles. Here, we found the Na ion and water molecules pre-intercalation can effectively activate stable Zn ion storage of δ-MnO2. Our results reveal that the resulted Zn//pre-intercalated δ-MnO2 battery delivers an extraordinarily high-rate performance, with a high capacity of 278 mAh g–1 at 1 C and up to 20 C, and a high capacity of 106 mAh g–1 can still be measured. The capacity retention is as high as 98% after charged–discharged up to 10,000 cycles benefiting from smooth Zn ion diffusion in the pre-intercalated structure. Further in situ /ex situ characterization confirms the superfast Zn ion diffusion in the pre-intercalated structure at room temperature. In addition, utilizing the well-chosen electrode material and modified polyurethane shell, we fabricated a quasi-solid-state healable Zn-δ-MnO2, which can be self-healed after multiple catastrophic damages, emphasizing the advanced features of aqueous Zn ion battery for wearable applications.

This paper describes the topochemical synthesis of Co-Ni layered double hydroxides (LDHs) from brucite-like Co-Ni hydroxides through a novel oxidative intercalation process employing bromine as an oxidizing agent, and their exfoliation into positively charged unilamellar nanosheets in formamide after anion-exchange treatment. In this protocol, hexagonal microplatelets of brucite-like Co-Ni hydroxides in variable composition were prepared by homogeneous precipitation of a mixed solution of divalent cobalt and nickel ions via hexamethylenetetramine hydrolysis. Subsequent treatment of the brucite-like Co-Ni hydroxides with excessive bromine in acetonitrile promoted partial oxidation of Co 2þ into Co 3þ , producing Br --intercalated Co-Ni LDHs inheriting the hexagonal morphology. This rational topochemical approach was applicable for realizing a pure phase of Co-Ni LDHs with nickel content up to 50% (metal content). Chemical analyses indicated that as-prepared Co-Ni-Br LDHs were unexceptionally characterized by a general chemical formula as(x e 0.5), a thermodynamically stable LDH structure with a M 2þ /M 3þ ratio of 2:1. We developed an ethanol-assisted anionexchange approach, which was effective in preventing carbonate contamination in preparing a variety of inorganic and organic anionic forms of Co-Ni LDHs. As-prepared NO 3 intercalated Co-Ni LDHs without substantial carbonate contamination were successfully exfoliated into unilamellar nanosheets bearing positive charges upon contact with formamide. The translucent nanosheet suspensions exhibited characteristic colors depending on the variable Co/Ni ratio.

This paper describes a simple complex-surfactant-assisted hydrothermal reduction approach to the facile synthesis of metal copper nanowires with average diameters of ∼85 nm and lengths of several tens of micrometers. These copper nanowires were formed through the reduction of the CuII−glycerol complexes (Cu(C3H6O3)) by phosphite (HPO3 2-) in the presence of surfactant sodium dodecyl benzenesulfonate (SDBS) at 120 °C. High-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED) indicate that the resulted nanowires had preferred [11̄0] growth direction. The formation mechanism for Cu nanowires had been properly proposed. Some influencing factors on the morphologies of the final products had also been discussed.

Artificial superlattice nanocomposites are successfully prepared by electrostatic heteroassembly of redoxable Co-Al or Co-Ni layered double hydroxide (LDH) nanosheets with graphene. The superlattice electrodes exhibit a high capacity up to ca. 650 F/g, which is approximately 6 times that of pure graphene. The composites are found to be capable of superfast charging and discharging, up to ca. 100 Hz, comparable with the high-power performance of graphene electrodes.

Doughnut-shaped ZnO microparticles have been grown through a hydrothermal reaction in citrate solution at 120 degrees C. FESEM reveals that these microparticles consist of regular arranged nanoplates, and there is a concave on the surface of each microparticle. The existence of citrate is vital to the formation of the complex microparticles. Room temperature photoluminescence measurements show strong UV band emission. The yellow and green emissions related to the structure defects can be barely observed, indicating the high crystalline perfection of these microparticles.

We demonstrate a facile solution-phase method for the synthesis of single-crystal, high aspect ratio, and ultrathin nanowires of hexagonal-phase Cu2S by thermal decomposition of CuS2CNEt2 in a mixed surfactant solvent of dodecanethiol and oleic acid at 160 degrees C. Cu2S nanowires can be controllably synthesized with a diameter as thin as 1.7 nm and length up to tens of micrometers; they are usually aligned in the form of bundles with a thickness of hundreds of nanometers. Based on the experimental results, the formation mechanism of the ultrathin nanowires has been properly proposed. Some key synthetic parameters, which have a significant effect on the sizes and shapes of the products, have also been investigated in detail. UV-vis spectroscopy measurement reveals that the resultant ultrathin nanowires show a strong quantum size effect.

This article describes a surfactant-assisted approach to the size-controlled synthesis of uniform nanorods of trigonal tellurium (t-Te). These nanorods were grown from a colloidal dispersion of amorphous Te (a-Te) and t-Te nanoparticles at room temperature, which was first formed through the reduction of (NH4)2TeS4 by Na2SO3 in aqueous solution at 80 degrees C. Nuclei formed in the reduction process had a strong tendency to grow along the [001] direction due to the inherently anisotropic structure of t-Te. The formation of Te nanorods could be ascribed to the confined growth through the surfactant adsorbing on the surfaces of the growing Te particles. By employing various surfactants in the synthesis system, Te nanorods with well-controlled diameters and lengths could be reproducibly produced by this method. Both the diameters and lengths of nanorods decreased with the increase of the alkyl length and the polarity of the surfactants. Te nanorods could also be obtained in mixed surfactants, where the different surfactants were used to selectively control the growth rates of different crystal planes. We also observed that the as-synthesized nanorods with uniform size could be self-assembled into large-area smecticlike arrays.