Nitrogen-Doped MOF-Derived Micropores Carbon as Immobilizer for Small Sulfur Molecules as a Cathode for Lithium Sulfur Batteries with Excellent Electrochemical Performance

Nitrogen-doped carbon (NDC) spheres with abundant 22 nm mesopores and 0.5 nm micropores are obtained by directly carbonization of nitrogen-contained metal organic framework (MOF) nanocrystals. Large S₈ and small S_2–4 molecules are successfully infiltrated into 22 nm mesopores and 0.5 nm micropores, respectively. We successfully investigate the effect of sulfur immobilization in mesopores and micropores on the electrochemical performance of lithium–sulfur (Li–S) battery based on NDC–sulfur hybrid cathodes. The large S₈ molecules in 22 nm mesopores can be removed by a prolonged heat treatment, with only small molecules of S_2–4 immobilized in micropores of NDC matrices. The NDC/S_2–4 hybrid exhibits excellent cycling performance, high Coulombic efficiency, and good rate capability as cathode for Li–S batteries. The confinement of smaller S_2–4 molecules in the micropores of NDS efficiently avoids the loss of active sulfur and formation of soluble high-order Li polysulfides. The porous carbon can buffer the volume expansion and contraction changes, promising a stable structure for cathode. Furthermore, N doping in MOF-derived carbon not only facilitates the fast charge transfer but also is helpful in building a stronger interaction between carbon and sulfur, strengthening immobilization ability of S_2–4 in micropores. The NDS–sulfur hybrid cathode exhibits a reversible capacity of 936.5 mAh g^–1 at 100th cycle with a Coulombic efficiency of 100% under a current density of 335 mA g^–1. It displays a superior rate capability performance, delivering a capacity of 632 mAh g^–1 at a high rate of 5 A g^–1. This uniquely porous NDC derived from MOF nanocrystals could be applied in related high-energy storage devices

Co₃O₄/Carbon Aerogel Hybrids as Anode Materials for Lithium-Ion Batteries with Enhanced Electrochemical Properties

A facile hydrothermal and sol–gel polymerization route was developed for large-scale fabrication of well-designed Co₃O₄ nanoparticles anchored carbon aerogel (CA) architecture hybrids as anode materials for lithium-ion batteries with improved electrochemical properties. The three-dimensional (3D) mesoporous Co₃O₄/CA hierarchical hybrids display an improved lithium storage performance and cycling stability, because of the intimate integration and strong synergistic effects between the Co₃O₄ nanoparticles and CA matrices. Such an interconnected Co₃O₄/CA hierarchical hybrid can effectively utilize the good conductivity, large surface area, 3D interconnected mesoporous structure, mechanical flexibility, chemical stability, and the short length of Li-ion transport of the CA matrix. The incorporation of Co₃O₄ nanoparticles into the interconnected CA matrix effectively reduces the number of active sites of Co₃O₄/CA hybrids, thus greatly increasing the reversible specific capacity and the initial Coulombic efficiency of the hybrids. The Co₃O₄/CA hybrid material displays the best lithium storage performance and good cycling stability as the Co₃O₄ loading content is up to 25 wt %, retains a Coulombic efficiency of 99.5% and a specific discharge capacity of 779 mAh g^–1 after 50 cycles, 10.1 and 1.6 times larger than the specific discharge capacity of 73 mAh g^–1 and 478 mAh g^–1 for Co₃O₄ and CA samples, respectively. The hierarchical hybrid nanostructures with enhanced electrochemical activities using a CA matrix framework can find potential applications in the related conversion reaction electrodes

Temario Provisional. Reunión Técnica de Negociadores Centroamericanos.

Series resistance of the obtained TiO2, Fe2O3/TiO2 and CdS/Fe2O3/TiO2 photoanodes. (DOCX 13 kb

Additional file 3: Figure S3. of CdS Nanoparticle-Modified Îą-Fe2O3/TiO2 Nanorod Array Photoanode for Efficient Photoelectrochemical Water Oxidation

The picosecond-resolved fluorescence transients of TiO2, Fe2O3/TiO2 and CdS/Fe2O3/TiO2 samples. (JPEG 1602 kb

Uniform Carbon Layer Coated Mn₃O₄ Nanorod Anodes with Improved Reversible Capacity and Cyclic Stability for Lithium Ion Batteries

A facile one-step solvothermal reaction route to large-scale synthesis of carbon homogeneously wrapped manganese oxide (Mn₃O₄@C) nanocomposites for anode materials of lithium ion batteries was developed using manganese acetate monohydrate and polyvinylpyrrolidone as precursors and reactants. The synthesized Mn₃O₄@C nanocomposites were characterized by X-ray diffraction, field-emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The synthesized tetragonal structured Mn₃O₄ (space group <i>I</i>41/<i>amd</i>) samples display nanorodlike morphology, with a width of about 200–300 nm and a thickness of about 15–20 nm. It is shown that the carbon layers with a thickness of 5 nm are homogeneously coated on the Mn₃O₄ nanorods. It is indicated from lithium storage capacity estimation that the Mn₃O₄@C samples display enhanced capacity retention on charge/discharge cycling. Even after 50 cycles, the products remains stable capacity of 473 mA h g^–1, which is as much 3.05 times as that of pure Mn₃O₄ samples. Because of the low-cost, nonpollution, and stable capacity, the carbon homogeneously coated Mn₃O₄@C nanocomposites are promising anode material for lithium ion batteries

Prussion Blue-Supported Annealing Chemical Reaction Route Synthesized Double-Shelled Fe₂O₃/Co₃O₄ Hollow Microcubes as Anode Materials for Lithium-Ion Battery

Fe₂O₃/Co₃O₄ double-shelled hierarchical microcubes were synthesized based on annealing of double-shelled Fe₄[Fe­(CN)₆]₃/Co­(OH)₂ microcubes, using Co­(AC)₂ as a Co²⁺ source to react with OH^– generated from the reaction of ammonium hydroxide and water. The robust Fe₂O₃ hollow microcube at the inner layer not only displays a good electronic conductivity but also acts as stable supports for hierarchical Co₃O₄ outside shell consisting of nanosized particles. The double-shelled hollow structured Fe₂O₃/Co₃O₄ nanocomposites display obvious advantages as anode materials for LIBs. The hollow structure can ensure the presence of additional free volume to alleviate the structural strain associated with repeated Li⁺-insertion/extraction processes, as well as a good contact between electrode and electrolyte. The robust Fe₂O₃ shell acts as a strong support for Co₃O₄ nanoparticles and efficiently prevents the aggregation of the Co₃O₄ nanoparticles. Furthermore, the charge transfer resistance can be greatly decreased because of the formation of interface between Fe₂O₃ and Co₃O₄ shells and a relative good electronic conductivity of Fe₂O₃ than that of Co₃O₄, resulting in a decrease of charge transfer resistance for improving the electron kinetics for the hollow double-shelled microcube as anode materials for LIBs. The Fe₂O₃/Co₃O₄ nanocomposite anode with a molar ratio of 1:1 for Fe:Co exhibits the best cycle performance, displaying an initial Coulombic efficiency of 74.4%, delivering a specific capacity of 500 mAh g^–1 after 50 cycles at a current density of 100 mA g^–1, 3 times higher than that of pure Co₃O₄ nanoparticle sample. The great improvement of the electrochemical performance of the synthesized Fe₂O₃/Co₃O₄ double-shelled hollow microcubes can be attributed to the unique microstructure characteristics and synergistic effect between the inner shell of Fe₂O₃ and outer shell of Co₃O₄

Metal–Organic Frameworks Derived Porous Core/Shell Structured ZnO/ZnCo₂O₄/C Hybrids as Anodes for High-Performance Lithium-Ion Battery

Metal–organic frameworks (MOFs) derived porous core/shell ZnO/ZnCo₂O₄/C hybrids with ZnO as a core and ZnCo₂O₄ as a shell are for the first time fabricated by using core/shell ZnCo-MOF precursors as reactant templates. The unique MOFs-derived core/shell structured ZnO/ZnCo₂O₄/C hybrids are assembled from nanoparticles of ZnO and ZnCo₂O₄, with homogeneous carbon layers coated on the surface of the ZnCo₂O₄ shell. When acting as anode materials for lithium-ion batteries (LIBs), the MOFs-derived porous ZnO/ZnCo₂O₄/C anodes exhibit outstanding cycling stability, high Coulombic efficiency, and remarkable rate capability. The excellent electrochemical performance of the ZnO/ZnCo₂O₄/C LIB anodes can be attributed to the synergistic effect of the porous structure of the MOFs-derived core/shell ZnO/ZnCo₂O₄/C and homogeneous carbon layer coating on the surface of the ZnCo₂O₄ shells. The hierarchically porous core/shell structure offers abundant active sites, enhances the electrode/electrolyte contact area, provides abundant channels for electrolyte penetration, and also alleviates the structure decomposition induced by Li⁺ insertion/extraction. The carbon layers effectively improve the conductivity of the hybrids and thus enhance the electron transfer rate, efficiently prevent ZnCo₂O₄ from aggregation and disintegration, and partially buffer the stress induced by the volume change during cycles. This strategy may shed light on designing new MOF-based hybrid electrodes for energy storage and conversion devices

Copper Doped Hollow Structured Manganese Oxide Mesocrystals with Controlled Phase Structure and Morphology as Anode Materials for Lithium Ion Battery with Improved Electrochemical Performance

We develop a facile synthesis route to prepare Cu doped hollow structured manganese oxide mesocrystals with controlled phase structure and morphology using manganese carbonate as the reactant template. It is shown that Cu dopant is homogeneously distributed among the hollow manganese oxide microspherical samples, and it is embedded in the lattice of manganese oxide by substituting Mn³⁺ in the presence of Cu²⁺. The crystal structure of manganese oxide products can be modulated to bixbyite Mn₂O₃ and tetragonal Mn₃O₄ in the presence of annealing gas of air and nitrogen, respectively. The incorporation of Cu into Mn₂O₃ and Mn₃O₄ induces a great microstructure evolution from core–shell structure for pure Mn₂O₃ and Mn₃O₄ samples to hollow porous spherical Cu-doped Mn₂O₃ and Mn₃O₄ samples with a larger surface area, respectively. The Cu-doped hollow spherical Mn₂O₃ sample displays a higher specific capacity of 642 mAhg^–1 at a current density of 100 mA g^–1 after 100 cycles, which is about 1.78 times improvement compared to that of 361 mA h g^–1 for the pure Mn₂O₃ sample, displaying a Coulombic efficiency of up to 99.5%. The great enhancement of the electrochemical lithium storage performance can be attributed to the improvement of the electronic conductivity and lithium diffusivity of electrodes. The present results have verified the ability of Cu doping to improve electrochemical lithium storage performances of manganese oxides

ZnS-Sb₂S₃@C Core-Double Shell Polyhedron Structure Derived from Metal–Organic Framework as Anodes for High Performance Sodium Ion Batteries

Taking advantage of zeolitic imidazolate framework (ZIF-8), ZnS-Sb₂S₃@C core-double shell polyhedron structure is synthesized through a sulfurization reaction between Zn²⁺ dissociated from ZIF-8 and S^2– from thioacetamide (TAA), and subsequently a metal cation exchange process between Zn²⁺ and Sb³⁺, in which carbon layer is introduced from polymeric resorcinol-formaldehyde to prevent the collapse of the polyhedron. The polyhedron composite with a ZnS inner-core and Sb₂S₃/C double-shell as anode for sodium ion batteries (SIBs) shows us a significantly improved electrochemical performance with stable cycle stability, high Coulombic efficiency and specific capacity. Peculiarly, introducing a carbon shell not only acts as an important protective layer to form a rigid construction and accommodate the volume changes, but also improves the electronic conductivity to optimize the stable cycle performance and the excellent rate property. The architecture composed of ZnS inner core and a complex Sb₂S₃/C shell not only facilitates the facile electrolyte infiltration to reduce the Na-ion diffusion length to improve the electrochemical reaction kinetics, but also prevents the structure pulverization caused by Na-ion insertion/extraction. This approach to prepare metal sulfides based on MOFs can be further extended to design other nanostructured systems for high performance energy storage devices

Cu₂ZnSnS₄ Nanoparticle Sensitized Metal–Organic Framework Derived Mesoporous TiO₂ as Photoanodes for High-Performance Dye-Sensitized Solar Cells

We present a facile hot injection and hydrothermal method to synthesize Cu₂ZnSnS₄ (CZTS) nanoparticles sensitized metal–organic frameworks (MOFs)-derived mesoporous TiO₂. The MOFs-derived TiO₂ inherits the large specific surface area and abundantly porous structures of the MOFs structure, which is of great benefit to effectively enhance the dye loading capacity, prolong the incident light traveling length by enhancing the multiple interparticle light-scattering process, and therefore improve the light absorption capacity. The sensitization of CZTS nanoparticles effectively enlarges the photoresponse range of TiO₂ to the visible light region and facilitates photoinduced carrier transport. The formed heterostructure between CZTS nanoparticles and MOFs-derived TiO₂ with matched band gap structure effectively suppresses the recombination rates of photogenerated electron/hole pairs and prolongs the lifespan of the carriers. Photoanodes based upon CZTS/MOFs-derived TiO₂ photoanodes can achieve the maximal photocurrent of 17.27 mA cm^–2 and photoelectric conversion performance of 8.10%, nearly 1.93 and 2.21 times higher than those of TiO₂-based photoanode. The related mechanism and model are investigated. The strikingly improved photoelectric properties are ascribed to a synergistic action between the MOFs-derived TiO₂ and the sensitization of CZTS nanoparticles