查看更多>>摘要：Rechargeable Lithium-Sulfur batteries (LSBs) are widely investigated as one of the most promising electrochemical energy storage devices due to their high energy density, low cost and environmental benignancy. However, poor conductivity, insufficient adsorption strength and sluggish multi-electron redox reactions restrict LSBs performance. Thus rational design of one–dimensional materials with good conductivity for sulfur, strong adsorption and catalytic abilities to lithium polysulfides (LiPSs), is necessary for improving the electrochemical behavior of lithium-sulfur batteries. Herein, we report Fe3C nanorods encapsulated in nitrogen-doped carbon nanotube (Fe3C@NCNT) as a promoter for sulfur cathode, in which CNT acting as a conductive network promotes ionic and electronic transfer, while “lithiophilic” heteroatom N immobilizes LiPSs through strong chemical bonding (Li–N bonds), and Fe3C accelerates the adsorption and conversion of LiPSs derived from its catalytic Fe3C site. Therefore, the Fe3C@NCNT as a promoter prolong the life of LSBs with the help of the synergistic effect of polarized N heteroatoms and catalytic effect of Fe3C. As a result, the composite cathode material delivers an outstanding initial capacity of 950 mAh g?1 at 0.5 C, and a capacity of 870 mAh g?1 after 100 cycles. This work proposes a feasible strategy to immobilize LiPSs and accelerate the conversion of LiPSs in high-performance lithium-sulfur batteries.
查看更多>>摘要：We present a study on the Curie transition of austenitic Ni-Mn-In full Heusler compounds when Mn atoms are replaced by Fe or Cu. The substituted compounds are designed to present a relevant magnetocaloric effect at the second order Curie transition of the austenitic phase near room temperature. We show that Fe and Cu modify the magnetic moments and interactions responsible of the localized magnetism in the L21 ordered cubic structure, resulting in a change of the Curie temperature and saturation magnetization of the compound. Neutron diffraction experiments and electron microscopy analysis were used to study the sites occupancy of doping atoms and the presence of secondary phases, thus possibly optimizing the annealing protocols to obtain homogeneous samples even at high Cu/Fe concentrations. On this basis, a series of quinary compounds with a tunable Curie temperature and high values of saturation magnetization (100–110 Am2/kg at 80 K) was successfully synthesized. The obtained results show the feasible fine tuning of the Curie temperature at which the peak of the magnetocaloric effect is realized, highlighting a new promising strategy to design graded regenerators for room temperature magnetocaloric applications.
查看更多>>摘要：The fabrication of heterojunctions with large interfacial contact areas is an effective technique for the development of high-performance photocatalysts. Step-scheme (S-scheme) heterojunctions with enhanced charge separation and strong redox ability have been regarded as promising photocatalytic materials in recent years. Herein, an S-scheme heterojunction based on tin niobate nanosheets and porous carbon nitride was designed and constructed using a one-plot calcination method. The multifunctional photocatalyst showed greatly enhanced photocatalytic activity and outstanding chemical stability toward hydrogen evolution and tetracycline hydrochloride (TCH) degradation, with reaction rates 1.64 and 12.28 times higher for TCH degradation and H2 production, respectively, compared to those of pristine g-C3N4. Meanwhile, TCH degradation experiments at different pH, TCH concentrations, catalyst dosages, and anions were evaluated. The main reactive species, possible degradation intermediates, and pathways were determined. The heterojunction exhibited a high surface area and broad visible-light absorption, which are responsible for the improved photocatalytic performance and high apparent quantum yield (AQY). In addition, an S-scheme charge transfer mechanism under an internal electric field was proposed following the results of in-situ irradiation X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), ESR, and Mott-Schottky measurements. This study offers a reasonable way to design another novel 2D/2D S-scheme heterojunction photocatalysts for energy and environmental applications.
查看更多>>摘要：A novel porous structure MnO-SiOx @C composite has been designed and prepared as an anode material for lithium-ion batteries through scalable spray pyrolysis and a subsequent annealing process. XRD, SEM, TEM, Raman, and BET measurements indicate that the MnO-SiOx @C composite displays a spherical mesoporous structure with SiOx particles, embedded in the porous MnO structure combined with carbon coated on the surfaces. The enhanced electrochemical performance can be attributed to the mutual segregation of the heterogeneous oxides of MnO and SiOx during delithiation and the buffer composition region at the origin of uniform carbon layers and abundant nanopores. In addition, the new phase Mn2SiO4, which is formed in the MnO-SiOx @C composite after 800 oC, can act as the joint between MnO and SiOx to restrain the strain force originating from the volume change during the charge and discharge process. As a result, the obtained MnO-SiOx @C composite exhibits significantly enhanced electrochemical performance in terms of high Coulombic efficiency, excellent rate capability and good cyclability.
查看更多>>摘要：In this work, a simple in-situ water-bath method is used to load Cu2O hollow nanospheres (named as H-Cu2O) on TiO2 nanosheets (named as TiO2-NS). H-Cu2O of 160–250 nm in diameter is uniformly supported on the surface of TiO2-NS. H-Cu2O has a novel hollow core-shell structure with a double shell. Specifically, the diameters of inner hollow spheres are 80–90 nm and the thickness of the outer shell and inner shell are about 40 nm and 25 nm, respectively. It is conjectured that the outer and inner shells of H-Cu2O can both provide adsorption and reaction sites, favoring the photocatalytic reaction. The UV–visible diffused reflectance spectra show that compared with TiO2-NS, the H-Cu2O/TiO2-2 sample with adding 80 mg of TiO2-NS shows a stronger visible light absorption. Furthermore, the steady-state photoluminescence (PL) and photocurrent spectra show that H-Cu2O/TiO2-2 has a weaker PL intensity at about 370 nm and 6 times higher photocurrent intensity than TiO2-NS, demonstrating that H-Cu2O/TiO2-2 has higher charge separation efficiency. Compared with TiO2-NS, the photocatalytic activity of H-Cu2O/TiO2-2 under UV light (λ ≤ 400 nm) increase by 6.3 times for the degradation of methyl orange. The improved photocatalytic activity can be attributed to the enlarged BET areas (6.1 m2 g-1/H-Cu2O/TiO2-2 vs. 3.8 m2 g-1/TiO2-NS), the enhanced light adsorption, and the improved charge separation efficiency. The reported in-situ water-bath method is simple, mild, and general, which could be extended to other novel composite materials.
查看更多>>摘要：As a crucial link in the application of hydrogen for an alternative clean energy, light-weight solid-state hydrogen storage materials, such as metal hydrides and complex hydrides, attract ever-growing attention, and they have a great application potential due to their high hydrogen storage densities. Intensive research performed on modifications of the composition of the materials to improve their unfavorable kinetics, the thermodynamics, and reversibility, put forward higher requirements to the characterization methods to study in-depth mechanisms of the improved hydrogen absorption and desorption performance. Fortunately, due to the high scattering cross-section of hydrogen and deuterium, neutron scattering techniques, including neutron diffraction, inelastic neutron scattering, small-angle neutron scattering, and neutron total scattering technology, have become powerful tools for characterizing hydrogen storage mechanism of metal hydrides and complex hydrides. This review summarizes the recent important outcome in developing advanced solid-state hydrogen storage materials via taking advantage of neutron scattering techniques.
查看更多>>摘要：Two new noncentrosymmetric multinary selenides, (KBa0.5)In2Se4 (1) and (K0.58Ba0.71)(Ga0.89In1.11)Se4 (2), have been synthesized using a high-temperature flux method at 1123 K. They crystallize in the tetragonal noncentrosymmetric space group I4cm with cell parameters: a = 8.0277(2), c = 6.7654(3) ?, V = 435.99(3) ?3 for 1; a = 8.0296(4), c = 6.5403(9) ?, V = 421.68(7) ?3 for 2 vs the orthorhombic centrosymmetric space group Fddd for BaIn2Se4. Their one-dimensional structures are constructed by [(MSe2)–]n (M = Ga, In) chains composed of MSe4 tetrahedra via sharing edges, and K+/Ba2+ cation occupying the interchain cavities. They both show moderate second-harmonic generation responses about 0.5 × AgGaS2@2.1 μm. UV-vis-NIR diffuse reflectance spectroscopy measurement shows that the optical band gaps of 1 and 2 are about 2.60 and 2.34 eV, respectively. Theoretical calculations are also carried out to analyze their electronic structures and optical properties.
查看更多>>摘要：Steel-Copper functionally graded material (FGM) has shown potential in extreme environments. Selective laser melting (SLM), one of the additive manufacturing technologies, is applied to form FGM with incompatibility between two or more alloys. In this work, the effects of process parameters on the interfacial characterization of 316L/CuCrZr FGM fabricated by SLM are addressed. A processing map for CuCrZr tracks on SLM processed 316L substrate is developed by the classification of surface morphologies. Furthermore, the interfacial characteristics, microscopic features, tensile properties and microhardness of 316L/CuCrZr FGM are investigated. Experimental results illustrate that the process parameters of regular scanned tracks in a range of linear energy density (LED) from 0.535 to 1.0625 J/mm are suitable for the formation of 316L/CuCrZr FGM. It is observed that the increase in laser power and scanning space and the decrease in scanning speed restrain the generation of cracks in the 316L region. Additionally, the ultimate tensile strengths of the vertically and horizontally integrated 316L/CuCrZr FGM are 318.2 ±7.2 MPa and 519.8 ±6.2 MPa, respectively. The microhardness decreases from 234.5 ±3.9 HV in 316L region to 130.25 ±5.65 HV in CuCrZr region. This provides valuable guidance for the fabrication of Steel-Copper FGM by SLM.
查看更多>>摘要：Phase equilibria in the Al-Cr-V system have an important role for designing of low-density Al containing refractory multiprincipal element alloys. In order to improve the literature data related to this system and contribute with the development of alloys with good oxidation resistance, the liquidus projection of the Al-Cr-V system is proposed for the first time in the present work. The experimental investigations were carried out via microstructural characterization of twenty-four as-cast alloys using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffractometry (XRD). Results showed no signs of ternary compounds and the limits of the primary precipitation fields are proposed. The primary precipitation field of BCC is preponderant in relation to those of the other phases. Me5Al8 aluminide with D82 crystal structure is present in both Al-Cr and Al-V systems (namely V5Al8 and the high temperature β-Cr5Al8) with a complete mutual solution of V and Cr forming a primary precipitation field connecting both diagrams (Al-V and Al-Cr). The VAl3 and CrAl4 primary precipitation fields were also determined. Three class II ternary invariant reactions are suggested based on experimental data: (UI) Liquid + α-Cr5Al8 ? Me5Al8 + CrAl4; (UII) Liquid + Me5Al8 ? VAl3 + CrAl4 and (UIII) Liquid + CrAl4 ? VAl3 + Cr2Al11. Four other class II and one class I ternary invariant reactions are suggested based on thermodynamic extrapolated data: (UIV) Liquid + Cr2Al11 ? VAl3 + CrAl7; (UV) Liquid + VAl3 ? V4Al23 + CrAl7; (UVI) Liquid + V4Al23 ? CrAl7 + V5Al47; (UVII) Liquid + V5Al47 ? CrAl7 + V2Al21 and (PI) V2Al21 + CrAl7 + Liquid ? (Al)-FCC.
查看更多>>摘要：Electrocatalytic water oxidation is a crucial process for many conversion and storage systems. Developing noble-metal-free oxygen evolution reaction (OER) electrocatalysts with high activity and long durability thus becomes immensely vital yet challenging. In this work, core-branch Co3O4 @CoNi-layered double hydroxide nanoarrays are developed on nickel foam with the assistance of metal-organic-frameworks template and atomic layer deposition technology, acting as active and durable electrocatalysts for OER. The introduction of CoNi-LDH significantly regulates the morphological and electronic structure of Co3O4, giving rise to high surface-active sites exposure, accelerated electron transfer, and optimal interaction with intermediate products. Together with the 3D self-supported and binder-free structure, the optimized Co3O4@CoNi-LDH/NF exhibits remarkable OER performances in terms of low overpotential, high OER current density, and low Tafel slope, which are even better than the benchmark IrO2 electrocatalyst. This study provides a new horizon for exploring biphasic core-branch materials for electrocatalysis and other energy-related applications.
NSTL
Elsevier