Dianzeng Jia

Decoration of Silica Nanoparticles on Polypropylene Separator for Lithium–Sulfur Batteries

A SiO2 nanoparticle decorated polypropylene (PP) separator (PP-SiO2) has been prepared by simply immersing the PP separator in the hydrolysis solution of tetraethyl orthosilicate (TEOS) with the assistance of Tween-80. After decoration, the thermal stability and the electrolyte wettability of the PP-SiO2 separator are obviously improved. When the PP-SiO2 separator is used for lithium-sulfur (Li-S) batteries, the cyclic stability and rate capability of the batteries are greatly enhanced. The capacity retention ratio of the Li-S battery configured with the PP-SiO2 separator is 64% after 200 cycles at 0.2 C, which is much higher than that configured with the PP separator (45%). Moreover, the rate capacity of the Li-S batteries using the PP-SiO2 separator reaches 956.3, 691.5, 621, and 567.6 mAh g-1 at the current density of 0.2, 0.5, 1, and 2 C, respectively. The reason could be ascribed to that the polar silica coating not only alleviates the shuttle effect but also facilitates Li-ion migration.

A series of new mixed-ligand complexes based on 3,6-bis(imidazol-1-yl)pyridazine: syntheses, structures, and catalytic activities

Seven new mixed-ligand complexes based on L [L = 3,6-bis(imidazol-1-yl)pyridazine], namely, [Ni(L)2(SCN)2]n (1), [Cu5(L)(1,2-BDC)4(μ3-OH)2]n (2), {[Cu4(L)2(1,3-HBDC)(1,3-BDC)(μ3-OH)4]·ClO4·2.6H2O}n (3), {[Ni(L)(1,4-BDC)H2O]·0.25H2O}n (4), [Co(L)(1,3,5-H2BTC)2H2O]n (5), {[Cu2(L)(2,6-PYDC)2(H2O)2]·4.4H2O}n (6), and {[Co(L)(4,4′-OBA)]·3.725H2O}n (7) [1,2-benzenedicarboxylic acid (1,2-H2BDC), 1,3-benzenedicarboxylic acid (1,3-H2BDC), 1,4-benzenedicarboxylic acid (1,4-H2BDC), 1,3,5-benzenetricarboxylic acid (1,3,5-H3BTC), 2,6-pyridine dicarboxylic acid (2,6-H2PYDC), and 4,4′-oxydibenzoic acid (4,4′-H2OBA)], have been synthesized by solvothermal reactions. Complexes 1 and 2 possess a two-dimensional (2D) layered structure, and the 2D framework of complex 1 can be rationalized to be a four-connected {44·62} topological sql network, while 2 exhibits a similar topological network with pentanuclear [Cu5(μ3-OH)2(μ2-COO−)6]2+ secondary building units (SBUs). Complex 3 presents an 8-connected sqc3 3D framework based on a chair-shaped [Cu4(μ3-OH)4]4+ SBU with a Schlafli symbol of {424·64}. Complex 4 displays a 3D framework with diamondoid topology, which includes L/Ni(II)/L helical chains. Complex 5 features a 1D chain structure formed by L ligands. Complex 6 shows a dinuclear structure, which is arranged into a 1D supramolecular chain by hydrogen-bonding interactions. The 3D framework of 7 presents a 4-connected porous architecture with a Schlafli symbol of {66}, the same as that of complex 4. The powder X-ray diffraction spectra, IR spectra, UV-vis absorption spectra and thermal stabilities of 1–7 have been investigated. Moreover, in the complex-catalyzed homocoupling reaction of 4-substituted aryl iodides, the catalytic activities of 1–7 have also been studied and discussed.

Preparation and exceptional adsorption performance of porous MgO derived from a metal–organic framework

Porous MgO materials have unique and highly attractive properties. In this paper, porous MgO microstructures with hexagonal and double hexagonal pyramid architectures (MgO-hex and MgO-dhp) were prepared simply by annealing Mg-based metal–organic framework [NH4][Mg(HCOO)3]. The monodisperse porous MgO-hex and MgO-dhp products inherit the morphologies of the [NH4][Mg(HCOO)3] precursors and have large surface areas. The adsorption performance of porous MgO-hex and MgO-dhp were systematically tested towards Congo red (CR) as a model pollutant. The adsorption capacities are 1380 mg g−1 for MgO-hex and 1413 mg g−1 for MgO-dhp toward CR after 150 minutes at the initial concentration of 1000 mg L−1. The prepared MgO materials exhibit potential applications in wastewater treatment. The experimental data were fitted by two isotherm models, and the adsorption isotherm obeys the Langmuir model. Moreover, the kinetic studies indicate that the kinetic data followed a pseudo-second-order model.

New complexes constructed from in situ nitration of (1H-tetrazol-5-yl)phenol: synthesis, structures and properties

Nine new complexes, {[Zn3(L1)2(OH)2]·H2O}n (1), [Ag2(L1)]n (2), {[Co(HL1)2(H2O)4]·2H2O} (3), [Cu3(L1)2(OH)2(H2O)]n (4), {[Cu7(HL1)2(L1)6(H2O)6]·11.1H2O}n (5), {[Cu(L1)(H2O)3]·8H2O}n (6), [Ag2(L2)]n (7), [Ag8(L3)4(H2O)]n (8) and [Cu(L3)(H2O)2]n (9) [H2L1 = 2,6-dinitro-4-(1H-tetrazol-5-yl)phenol, H2L2 = 2,4,6-trinitro-3-(1H-tetrazol-5-yl)phenol, H2L3 = 2,4-dinitro-6-(1H-tetrazol-5-yl)phenol], have been solvothermally synthesized via in situ nitration from 4-(1H-tetrazol-5-yl)phenol, 3-(1H-tetrazol-5-yl)phenol and 2-(1H-tetrazol-5-yl)phenol precursors as well as nitrate salts as nitration reagents and structurally characterized by single-crystal X-ray diffraction, infrared spectroscopy (IR), elemental analysis, powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA). The structures of the complexes vary from 3D frameworks for 1, 4 and 7, 2D networks for 2, 5 and 8, 1D chains for 6 and 9, to a discrete 0D structure for 3, showing 2D supramolecular structures by interlayer π–π stacking. Topological classification of 2D and 3D architectures was performed, disclosing a variety of topological symbols: (42·6)2(44·62·88·10) for 1, (43)2(46·66·83) for 2, (46)2(412·612·84) for 4, (63) for 5 and (45·6)(47·63)(418·616·82) for 7. The contrast of 1–9 reveals that ligands and metal salts have important influences on adjusting the crystal structures; notably, the coordination modes of the ligands can also tune the structures of 4–6 which possess the same ligands and nitration agents. The solid-state UV-vis spectra and band gap energy of the nine complexes were investigated. In addition, the luminescence properties (for complexes 1–3, 7 and 8) and magnetic properties (for complexes 3–6 and 9) were also discussed.

High-performance supercapacitors based on conductive graphene combined with Ni(OH)2 nanoflakes

A green and facile strategy is reported for the synthesis of a three-dimensional (3D) graphene nanosheets (GNS)/Ni(OH)2 composite for use as a supercapacitor material. During this process, graphene oxide was reduced to graphene and Ni(OH)2 was attached in it to form the GNS/Ni(OH)2 composite via a chemical precipitation route without any complicated procedures. The product was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The analyses indicated that the Ni(OH)2 sheets were well interwoven on the surfaces of the graphene nanosheets. Furthermore, the composite was electrochemically tested by cyclic voltammetry, galvanostatic charge/discharge, specific capacitance, and by assessing its cycle life. The GNS/Ni(OH)2 composite exhibited a high specific supercapacitance of 2053 F g−1 at a current density of 0.3 A g−1 in 6 M KOH electrolyte and a long cycle life, along with 97% specific capacitance remaining after 1000 cycles. The GNS/Ni(OH)2 composite had superb electrochemical performance compared to bare Ni(OH)2, which could be attributed to its architecture. These results suggest that the GNS/Ni(OH)2 composite could have potential application as a supercapacitor material.

Hierarchical porous carbon spheres constructed from coal as electrode materials for high performance supercapacitors

Hierarchical porous carbon spheres (PCS) are prepared by a simple one-pot spray pyrolysis of coal oxide solution without any further activation process. The specific surface area and total pore volume of the resultant carbon spheres are increased significantly with the increase of spray pyrolysis temperature. When evaluated as electrode materials for supercapacitors in 6 M KOH electrolyte, the PCS exhibits a high specific capacitance 227 F g−1 at a current density of 1 A g−1 and outstanding cycling stability after 10u2006000 charge/discharge cycles at a current density of 2 A g−1. In symmetric supercapacitor, the specific capacitance of the sample PCS-8 is 180 F g−1 at a current density of 0.2 A g−1 and has excellent rate capability. The proposed strategy offers a facile and green method to produce porous carbon spheres from coal, and has potential application in energy storage.

Cost-effective synthesis of bamboo-structure carbon nanotubes from coal for reversible lithium storage

Carbon nanotubes (CNTs) with special structures offer great benefits for energy storage applications. Herein, we reported the facile and cost-effective synthesis of bamboo-structure CNTs (B-CNTs) using coal as the precursor through an effective arc discharge process. When evaluated as an anode material for lithium-ion batteries, the B-CNTs afford a high reversible capacity of 450.1 mAxa0h g−1, even after 100 cycles, as well as excellent rate performance over widely varied current densities, far superior to those of commercially available graphite anodes.

Synthesis and improved photochromic properties of pyrazolones in the solid state by incorporation of halogen.

Four novel photochromic pyrazolones have been prepared by introducing halogen atoms as substituents on the benzene ring. All as-synthesized compounds exhibited excellent reversible photochromic performances in the solid state. Upon UV light irradiation, the as-synthesized compounds can change their structures from E-form to K-form with yellow coloration. Further processed by heating, they rapidly reverted to their initial states at 120°С. Their photo-response and thermal bleaching kinetics were detailed investigated by UV absorption spectra. The results showed that the time constants were higher than that of our previously reported compounds at least one order of magnitude and the rate constants of the as-synthesized compounds were significantly influenced by the size and electronegativity of different halogen atoms. The fluorescence emission were modulated in a high degree via photoisomerization of pyrazolones, which might be due to the efficient energy transfer from E-form to K-form isomers for their partly overlaps between their E-form absorption spectra and K-form fluorescence spectra.

Solid-state photochromic behavior of pyrazolone 4-phenylthiosemicarbazones

Solid-state photochromic materials have attracted much more attention due to their actual potential applications in photoactive devices. Here, three new compounds (1-phenyl-3-methyl-4-(3-fluoro/chloro/bromobenzal)-5-hydroxypyrazole 4-phenylthiosemicarbazones) were synthesized, which exhibited reversible solid state photochromic properties upon UV/Vis light irradiation. Their photochromic properties, first-order kinetics and fatigue resistance were investigated by time-dependent UV-Vis absorption spectroscopy. The results showed that their fatigue resistance and addressability were enhanced with the increase in the electron-withdrawing ability of the substituents on the phenyl group at the 4-position of the pyrazolone ring. Thus, 1-phenyl-3-methyl-4-(3-fluorobenzal)-5-hydroxypyrazole 4-phenylthiosemicarbazone exhibited good photochromic properties and high fatigue resistance. Based on single crystal X-ray diffraction and FT-IR analyses, the photochromic mechanism involved intra/intermolecular proton transfer.