Dynamically Evolving Multifunctional Protective Layer for Highly Stable Potassium Metal Anodes.

The construction of an artificial protective layer is an effective method to solve the issues, such as uncontrolled dendrite growth and an unstable solid electrolyte interphase, at the K metal anode. This study proposes a new dynamic evolution strategy that integrates the advantages of previous in situ and ex situ fabrication processes. A multifunctional protective layer enriched with K-Ge alloy is prepared on the K metal electrode by simple surface modification and in situ reduction via an electrochemical process. The protective layer has good potassiophilicity, mechanical flexibility, and high ionic conductivity, which can inhibit dendrite growth and reduce side reactions. The protected K electrode with a protective layer exhibits dendrite-free K plating/striping behavior, and the symmetric cell can run stably for over 1000 h at 1 mA cm-2 and 1 mAh cm-2. Notably, full cells based on this electrode also present excellent rate and cycling performance compared to those of the bare K electrode. This peculiar strategy will open a new avenue for metal anode protection and can be extended to other high-energy battery systems.

A Constrained Assembly Strategy for High-Strength Natural Nanoclay Film.

Developing high-performance materials from existing natural materials is highly desired because of their environmental friendliness and low cost; two-dimensional nanoclay exfoliated from layered silicate minerals is a good building block to construct multilayered macroscopic assemblies for achieving high mechanical and functional properties. Nevertheless, the efforts have been frustrated by insufficient inter-nanosheet stress transfer and nanosheet misalignment caused by capillary force during solution-based spontaneous assembly, degrading the mechanical strength of clay-based materials. Herein, a constrained assembly strategy that is implemented by in-plane stretching a robust water-containing nanoclay network with hydrogen and ionic bonding is developed to adjust the 2D topography of nanosheets within multilayered nanoclay film. In-plane stretching overcomes capillary force during water removal and thus restrains nanosheet conformation transition from nearly flat to wrinkled, leading to a highly aligned multilayered nanostructure with synergistic hydrogen and ionic bonding. It is proved that inter-nanosheet hydrogen and ionic bonding and nanosheet conformation extension generate profound mechanical reinforcement. The tensile strength and modulus of natural nanoclay film reach up to 429.0 MPa and 43.8 GPa and surpass the counterparts fabricated by normal spontaneous assembly. Additionally, improved heat insulation function and good nonflammability are shown for the natural nanoclay film and extend its potential for realistic uses.

Chlorine-assisted synthesis of CuCo2S4@(Cu,Co)2Cl(OH)3 heterostructures with an efficient nanointerface for electrocatalytic oxygen evolution.

The demand for sustainable energy sources urges the development of efficient and earth-abundant electrocatalysts. Herein, chlorine assisted ion-exchange and in-situ sulfurization processes were combined to construct CuCo2S4@(Cu,Co)2Cl(OH)3 heterostructures from Cu(OH)2 nanoarrays. Chlorine element in the cobalt source stimulated the formation of (Cu,Co)2Cl(OH)3 precursor, and further facilitated partial transformation of the precursor to CuCo2S4 on the surface to achieve composite structure. The mixed valences of Co element (Co3+ in CuCo2S4 and Co2+ in (Cu,Co)2Cl(OH)3) and OS interpenetrated nanointerface in the composite catalysts provided low electron transfer resistance for good alkaline oxygen evolution reaction (OER) activities. In 1 mol L-1 KOH electrolyte, the overpotentials of the optimal composite catalyst reached 253 and 290 mV respectively at the current density of 20 and 50 mA cm-2, which is comparable to the activity of commercial Ir/C (281 mV@20 mA cm-2). These findings could provide opportunities for designing effective and inexpensive composite electrocatalysts through nanointerface engineering strategy.

Ammonia-induced synergistic construction of Co3O4@CuO microsheets: An efficient electrocatalyst for oxygen evolution reaction.

Copper-based materials have attracted increasing attention for their earth-abundant and cheap characters for water splitting application. In the present work, a combined structure of Co3O4 nanoparticles and CuO microsheets was constructed in an aqueous system and studied as an efficient oxygen evolution reaction (OER) electrocatalyst. NH3 molecules as the ligand of metal ions (Cu2+ and Co2+) played vital roles for the uniform growth of Co3O4@CuO microsheets. The synergetic contribution of the two components made the composite samples behave excellent OER activity and fast kinetics both on glassy carbon electrode (GCE) and nickel foam (NF) substrates in alkaline medium. The remarkable small overpotentials (310 and 394 mV) can be obtained for CuO-Co-0.2/GCE sample at current densities of 1 and 10 mA/cm2 in 1.0 mol L-1 KOH (pH = 13.6). The in-situ deposited CuO-Co-0.2/NF achieved in the aqueous synthetic system demonstrates superior (structural and electrochemical) stability for 20 h-OER performance.

Time-dependent synthesis of BiO2-x/Bi composites with efficient visible-light induced photocatalytic activity.

A series of BiO2-x/Bi nanocomposites were prepared via a time-dependent aqueous method, with the induction of lactic acid. The interaction of Bi3+ and C3H6O3 in stock solution determined the formation of nonstoichiometric BiO2-x as the precursor, subsequent reduction reaction at acid circumstance (pH = 3) produced combined composition of BiO2-x nanosheets and Bi particles. Multiple valence states of Bi element (Bi0, Bi3+ and Bi5+) in the composite sample make it possible to manipulate the band structures of photocatalysts. The BiO2-x/Bi composites with appropriate composition exhibited superior photocatalytic performance in the degradation of colorless bisphenol A (BPA) under visible-light irradiation. The O2- and OH radicals were detected as valid active species in the degradation process from ESR analysis. The photocatalytic mechanism over BiO2-x/Bi composites was proposed on the consideration of electron-hole separation and the interfacial charge transfer.

Aqueous Synthesis of Mn3O4 Nanoparticle@MnOOH Nanobelt Heterostructures.

A combined heterostructures with Mn3O4 nanoparticles attached to MnOOH nanobelts were prepared via an aqueous oxidation method at 90 °C with H2O2 as oxidant. The crystalline structures and morphologies of the as-prepared samples were detected by X-ray powder diffraction (XRD), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM) analysis, and the forming mechanism of Mn3O4@MnOOH nanomaterials was discussed. Crystalline composition and morphologies of samples changed with reaction time and crystallinity of Mn(OH)2 precursor. ß-MnOOH nanoplates can be obtained in the initial reaction, then it transformed to γ-MnOOH nanobelts and/or Mn3O4 nanoparticles as reaction time increasing. The ratio of Mn3O4 in Mn3O4@MnOOH nanomaterials increased with the better crystallinity of Mn(OH)2 precursor. The as-prepared Mn3O4@MnOOH nanomaterials with varied compositions were used for degradation of Rhodamine B (RhB) in acid condition. The degradation reactions carried out in acid condition without stimulated light sources. The results showed that the manganese heterostructures had good activity based on synergy of Mn3O4 and MnOOH nanocrystals.

pH-dependent synthesis of iodine-deficient bismuth oxyiodide microstructures: Visible-light photocatalytic activity.

Bismuth oxyiodides have exhibited high potential for applications in visible-light photocatalytic environmental remediation and solar energy conversion. In this work, a series of iodine-deficient bismuth oxyiodides (Bi4O5I2, Bi7O9I3, Bi5O7I) can be simply prepared through a pH-dependent aqueous procedure with feeding Bi/I ratio of 2:1. The compositions of the Bi-based oxyiodides are closely related to acid-base circumstances, with Bi4O5I2 formed in weakly acidic medium (pH = 5) and Bi7O9I3, Bi5O7I in basic medium (pH = 8 and 11). Morphology differences of nanosheet-assembled Bi4O5I2, Bi7O9I3 architectures and rod-like Bi5O7I microstructures demonstrate different crystalline characters and construction of Bi-based oxyiodide crystals. UV-vis DRS results revealed good visible-light absorptions of Bi4O5I2 and Bi7O9I3 architectures and appropriate band structures for photocatalytic reactions, on comparison to Bi5O7I microrods. Low electrochemical impedance of Bi7O9I3 microflowers with sheet-like units further facilitated the separation of e--h+ carriers in the degradation process. Accordingly, among the bismuth oxyiodide samples, Bi7O9I3 displayed prominent visible-light degradation performance for colorless bisphenol-A (BPA) due to the direct photoexcitation process.

CTAB induced hierarchical bismuth microspheres for visible-light photocatalytic study.

Nanosheet constructed bismuth microspheres were prepared through an aqueous reduction approach in the presence of CTAB molecules, with initial formed BiOCl as the precursor and hydrazine hydrate as the reductant. The flower-like morphology and platelet units of BiOCl precursor determined the evolution of hierarchical Bi microspheres through a morphology-heredity process. Trisodium citrate was introduced to keep the Bi microspheres from oxidation, the high purity in composition are beneficial to eliminate the influence of bismuth oxides. Photocatalytic properties of the hierarchical Bi microspheres were investigated under visible-light irradiation by taking the degradation of rhodamine B (RhB) dye and colorless bisphenol A (BPA) as probe reactions. 99.7% of RhB and 47.4% of BPA degradation in 3h indicate good photocatalytic property of the hierarchical Bi microspheres. Results of storing detection and recycled experiments revealed good structure stability and photocatalytic stability of the Bi microspheres, these properties are vital for practical applications of the materials. The formation mechanism of Bi microspheres and relative degradation mechanism are also proposed on the basis of experimental data.

Synthesis of Co3O4 nanoclusters via an EDTANa4-assisted route for enhanced electrochemical application.

Three-dimensional (3D) Co3O4 nanoclusters were fabricated with the assistance of tetrasodium ethylene diamine tetraacetic acid (EDTANa4) through a one-pot wet-chemical reaction, featuring self-limiting assembly of building blocks and controlled regrowth process. The molar ratio of Co2+ and EDTANa4 plays a key role in building initial clusters as blocks, and the amount of NaOH effects the regrowth process. A possible formation mechanism for the Co3O4 nanoclusters was proposed based on the characterization results of X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The designed hierarchical Co3O4 nanoclusters exhibit a high specific capacitance of 221Fg-1 at a current density of 2Ag-1 in 2molL-1 KOH electrolyte.

Facile and Efficient Synthesis of Bismuth Nanowires for Improved Photocatalytic Activity.

An aqueous reduction method was reported for the synthesis of bismuth nanowires (Bi NWs) 5-10 nm in diameter and several micrometers in length under the guidance of PVP molecules. The reactions were performed at 80 °C by reducing bismuth chloride with sodium hypophosphite first in acid and then under neutral circumstances. The key to successful preparation of the Bi NWs is regulation of the reduction speed by control of the pH value. The morphology evolution of the samples was also found to have a strong dependence on the reaction parameters, including the introduction amount and molecular weight of PVP molecules. A solid-solution-solid (SSS) mechanism was proposed for the nucleation and growth of Bi NWs in our strategy. The as-prepared Bi NWs exhibit excellent visible-light photocatalytic activities for the degradation of the organic pollutant Rhodamine B (RhB) and colorless bisphenol A (BPA). The good recyclability of the Bi NWs on RhB photodegradation demonstrates the possibility of their practical applications.

Hierarchical Bi based nanobundles: an excellent photocatalyst for visible-light degradation of Rhodamine B dye.

Hierarchical Bi based nanobundles were self-assembled via an aqueous reduction approach using hydrazine hydrate as reductive agent, and were used as photocatalysts for the degradation of Rhodamine B (RhB) under visible light. PVP molecules were designed as inducing agent to construct the Bi based nanobundles. The as-obtained samples were characterized by X-ray diffraction (XRD), energy dispersive X-ray (EDX), thermogravimetric-differential thermal analyzer (TG-DTA), infrared spectroscopy (IR) and field emission scanning electron microscopy (FESEM) to get clear information of the crystals. A possible formation mechanism for the interesting architectures was proposed in the paper. The Bi based nanobundles exhibited excellent photocatalytic activity and good cycling performance towards photodegradation of RhB under visible light. The pH-sensitive degradation can reach 96% in degradation rate after 90 min, which indicates potential applications of the Bi based nanobundles on the degradation of organic pollutants. Degradation mechanism is proposed on the combination of Bi and BiOCl crystals.

Room temperature synthesis of 2D CuO nanoleaves in aqueous solution.

A simple room temperature method was reported for the synthesis of CuO nanocrystals in aqueous solution through the sequence of Cu(2+) → Cu(OA)2 → Cu(OH)2 → Cu(OH)(2-)4 → CuO. Sodium oleate (SOA) was used as the surfactant and shape controller. The as-prepared samples were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible absorption spectroscopy (UV-vis) and differential thermal analysis (DTA). It can be seen that 1D Cu(OH)(2) nanowires were first obtained from Cu(OA)(2) and, at room temperature, converted into 2D CuO nanoleaves (CuO NLs) in a short time under a weakly basic environment. On prolonging the reaction time, the top part of these 2D nanoleaves branched and separated along the long axis to form 1D rod-like nano-CuO because of the assistance of SOA. A possible transformation mechanism of Cu(OH)(2) to CuO nanostructures at room temperature in aqueous solution is discussed. The transformation velocity can be controlled by changing the pH value of the system. The prepared CuO NLs were used to construct an enzyme-free glucose sensor. The detecting results showed that the designed sensor exhibited good amperometric responses towards glucose with good anti-interferent ability.

A facile synthesis of Cu(2)O/SiO(2) and Cu/SiO(2) core-shell octahedral nanocomposites.

We report here a simple approach to the synthesis of Cu(2)O/SiO(2) core-shell nanocomposites in water solution. The Cu(2)O cores have a perfect octahedral structure with uniform size of about 200-300 nm. A compact SiO(2) shell 9 nm in thickness is located at the surfaces of Cu(2)O octahedra, and it is composed of fine SiO(2) nanoparticles. During the depositing of the SiO(2) particles, as we presumed, dynamic absorbing and disengaging of Na(+) at the interface of Cu(2)O octahedra and the solution made it possible for the formation of Cu-O-Si bonds between core and shell in the composites. The existence of Cu-O-Si bonds in our core-shell composite can be substantiated by peak changes at 1236 and 1080 cm(-1) in the FT-IR spectra. This is the reason why the SiO(2) shell is so compact and uniform. Moreover, these Cu(2)O/SiO(2) core-shell octahedra were further used as precursors, depending on a simple disproportionation reaction of Cu(2)O in acid, to easily achieve Cu/SiO(2) movable multicore-shell octahedral nanocomposites. In the final Cu/SiO(2) core-shell composite, the thin SiO(2) octahedral shell was held, inside of which formed several free Cu nanoparticles 50-80 nm in size. Studies on the Cu(2)O/SiO(2) core-shell octahedral composites and Cu/SiO(2) movable multicore-shell octahedral nanocomposites would be a good thing not only for fundamental research but also for applications.

[Analysis on processing mechanism of calamine].

OBJECTIVE: To study processing method and mechanism of Calamine. METHOD: Thermogravimetry analysis method and nano-technology were adopted to analyze and synthesize the components in Calamine, Tetracycline was took as the comparison drug to determine the antibacterial activity of Calamine and its components. RESULT: A part of zinc carbonate in Calamine was decomposed into zinc oxide when processing, and the particle size was smaller than before. The antibacterial activity of Calamine is decided by the content and particle size of zinc oxide, and has nothing with zinc carbonate. The more content and the smaller particle size of zinc oxide, the more powerful antibacterial activity of Calamine. CONCLUSION: The content and the particle size of zinc oxide can be the important targets in the processing of Calamine.

Influence of octadecyl dihydrogen phosphate on the formation of active super-fine calcium carbonate.

A carbonation process for the synthesis of active super-fine calcium carbonate particles from Ca(OH)(2) slurry at room temperature using a CO(2)-N(2) gas mixture was investigated. Industrial octadecyl dihydrogen phosphate (A) was added as a size-controlling additive and modifier in different reaction periods according to the pH of the medium. Analysis of the reaction products led to the conclusion that the addition of A in the digestion period could inhibit the crystal growth of calcium carbonate, while the addition of A at pH 7 of the medium could modify the surface character of the calcium carbonate particle, which was found to exhibit hydrophobic properties. From transmission electron microscopy (TEM), the hydrophobic property was attributed to the deposition of calcium alkyl phosphates, produced in the reaction mixture, onto the surface of calcium carbonate particle. IR spectra and TGA analysis of the obtained products indicated that A was bound onto the crystalline CaCO(3).