查看更多>>摘要：The combination of active materials and carbon nanotubes (CNTs) provides an effective way to enhance battery capacity and optimize cycle performance. In the present study, the powder electrodeposition technology is employed to synthesize the NiO-Ni/CNTs composite for the first time. This technique contains the following steps. The CNTs are negatively charged by pre-discharge in lithium-ion batteries. Then, the negatived CNTs are uniformly dispersed in the NiCl_2 plating solution by electrostatic repulsion, and the Ni ions are in situ reduced and deposited onto the CNTs. The close combination of CNTs and NiO-Ni improves the overall conductivity and structural stability. As electrode of lithium-ion battery, the reversible capacity is improved due to the coordination of the Ni metal in the mixture of the composite electrode. Besides, the reversible capacity of the composite electrode is 851 mA h g~(-1) at 50 mA g~(-1) after 50 cycles. The "Powder electrodeposition" method in the current work provides a new way for the preparation of other similar powder composite materials. Furthermore, the problem that the traditional electrodeposition process is difficult to apply in the powder materials will be solved.
查看更多>>摘要：Transition metal oxides have achieved tremendous attention in the field of supercapacitor devices due to their outstanding structural properties and capacitive behavior. Herein, a porous a-MoO_3 microspheres (A-SMO) were synthesized with the aid of CrCl_3.6H_2O via a facile hydrothermal reaction and subsequent annealing treatment. The results showed that CrCl_3.6H_2O plays a crucial role in manipulating morphology and increasing the specific surface area of the as-prepared products. Moreover, annealing treatment could transform the crystal structure from metastable hexagonal M0O_3 to stable orthogonal MoO_3, which is more beneficial for electron storage due to the layered crystal structure. Furthermore, the A-SMO displayed an excellent specific capacitance of 201.4 F g~(-1) compared with the pristine MoO_3 (MO) of 62.0 F g~(-1) and the annealed MO (A-MO) of 186.5 F g~(-1) at 0.2 A g~(-1), when they were directly served as supercapacitor electrodes. This research demonstrates that the as-obtained a-MoO_3 microspheres can serve as promising electrode materials for supercapacitors.
查看更多>>摘要：Flexible supercapacitors (SCs) can usually be used as potential candidates for small flexible electronic devices, due to their good flexibility, rapid charge-discharge ability, and long-term cycling stability. Here, a facile solvothermal approach has been developed to prepare flexible and high-performance nitrogen-doped Ti_3C_2 MXene film electrodes for symmetric SCs. The effects of different solvents on the atomic structure, surface microstructure, and charge storage mechanism of N-doped Ti_3C_2 films were studied to explore the defect engineering of MXene for the enhancement of capacitive performance. Because of the comprehensive effects of the mixed solvents (diethanolamine (DEA) and isopropyl alcohol (IPA)) and the large inner pressure under the ex situ solvothermal process, the as-prepared N-doped Ti_3C_2 film fabricated from DEA and IPA with a volume ratio of 1:1 (IPAD-Ti_3C_2) shows a superhigh capacitance of 2846.5 F cm~(-3) at 5 mV s~(-1) and excellent stability. In addition, the IPAD-Ti_3C_2 film-assembled symmetric SC delivers a relatively large volumetric energy density of 64.0 Wh L~(-1) and a superhigh volumetric power density of 118,033.3 W L~(-1) at 1000 mV s~(-1). This work provides a feasible solution to improve the application potential of MXenes and, more broadly, binary metal carbides by ex situ nitrogen doping with mixed solvents.
查看更多>>摘要：Multi-principal-element alloys (MPEAs) are a wide class of materials currently at the center of numerous investigations. Key-issues with MPEAs are related with controlling the onset of (i) long-range order and (ii) phase separation, both processes being in general detrimental to the properties. While trends (i) and (ii) are strongly dependent on the precise proportions of metallic elements around the reference equiatomic MPEA, the tremendously large composition space makes it a tricky task to heuristically identify optimized MPEAs. In practice, this often leads to undesired second-phase ordered particles. This deficiency emphasizes the relevance of modelling and simulation tools designed to facilitate the exploration of MPEA composition spaces. In this atomic-scale work, we propose a "composition-constrained" point mean-field formalism resting on alloy pair energetics, to investigate trends (i) and (ii). This formalism is currently applicable to a wide panel of such systems built from ~ 30 chemical elements. Its application to several MPEAs along the AlCoCrFeNi → AlCrFeMnNi→ AlCrFeMnMo sequence evidences striking differences between these systems, and demonstrates its efficiency to get at-a-glance information about (i) and (ii) features for various MPEAs. The flexibility of the proposed simulation approach makes it easily employable in conjunction with experiments on well-equilibrated MPEA samples, for thermodynamic characterizations of MPEAs.
查看更多>>摘要：In this work, to enhance the mineralization of the organic dyes, the g-C_3N_4(Ag)/Gr/TiO_2 Z-scheme photo-catalyst was successfully prepared by hydrothermal method. The XRD and XPS results showed that the nanocomposite was constructed. The SEM and EDS results showed that the morphology of g-C_3N_4(Ag)/Gr/ TiO_2 was that TiO_2 nanoparticles distributed on the surface of the Gr/g-C_3N_4 layers. The photocatalytic performance of the prepared samples was evaluated by the photocatalytic degradation and mineralization of RhB under visible light irradiation. The degradation efficiency of RhB on g-C_3N_4(Ag)/Gr/TiO_2 reached 99.7% within 2 h, and the kinetic rate (0.0431 min~(-1)) was 7.1, 7.1, 2.2, 2.0 and 1.3 times higher than those of g-C_3N_4, TiO_2, g-C_3N_4(Ag)/Gr, g-C_3N_4/TiO_2, and g-C_3N_4/Gr/TiO_2, respectively. The total organic carbon (TOC) removal results showed that the mineralization efficiency of RhB on this composite was as high as 74.5% after 2 h of reaction time. During the photocatalytic process, it was speculated that Gr acted as the electron transporter between TiO_2 and g-C_3N_4, which reduced the recombination efficiency of photo-generated charge carriers, and silver clusters acted as an electron reservoir to accelerate the reduction reaction of photo-generated electrons on the g-C_3N_4 conduction band, and further improved the photocatalytic performance.
查看更多>>摘要：In recent years, molybdenum disulfide (MoS_2) with sandwich structure has been widely studied as cathode material of aqueous rechargeable zinc-ion batteries (ARZIBs), but inherent low capacity and short cycle life limit its further development. Here, we synthesized a novel hydrophilic spherical 1T-MoS_2 through hexadecyl trimethyl ammonium bromide (CTAB) template-assisted hydrothermal reaction as cathode materials for ARZIBs and systematically study its mechanism of electrochemical enhancement. The results suggest that stable spherical MoS_2 was prepared by in-situ reduction of molybdate ion under the electrostatic absorption of CTAB template and 0 element introduced by ethylene glycol (oil-phase solvent) not only increases the hydrophilicity of the material and facilitates the intercalation of ammonium ions and water molecules, but also promotes the formation of the 1 T phase by changing the electronic structure. Consequently, this modified electrode exhibits a reversible capacity of 110 mAh g~(-1) at the current density of 1.0 A g~(-1), and the capacity retention rate is up to 90% after 500 cycles, showing excellent cycling stability and rate performance.
查看更多>>摘要：The uncontrollable dendritic behavior and volume expansion in alkali metal anodes have led to short-circuit issues and low Coulombic efficiency which significantly hamper the commercialization of alkali metal anodes. To address these issues, we report the fabrication of a novel functional host in which the alkaliphilic Cu(OH)_2 nanowires were uniformly grown on Cu foam (denoted as Cu(OH)_2-NWs@CF) for Li/Na anodes. The 3D network structure of Cu(OH)_2-NWs@CF with high specific surface area can not only effectively reduce local current density to guide homogeneous deposition of Li~+, leading to more controllable nucleation sites and dendrite-free Li deposition, but also minimize the volumetric strain during repeated Li/Na stripping/ plating processes, mitigating the volume change of the batteries. Benefitting from these advantages, the as-prepared Li/Na@CF composite anodes exhibit outstanding long-term cycle stability and structure maintaining ability. In particular, the Li@CF-based symmetric cells deliver elevated cycling performance under a moderate polarization voltage for nearly 1200 h at a current density of 1 mA cm~(-2). Similarly, the Na@CF-based symmetric cells can also cycle stably for 800 h at a current density of 0.5 mA cm~(-2). Furthermore, the Li@CF||LFP full cells show significantly improved rate capability and high cycle stability (97% capacity retention after 100 cycles). Our work demonstrates the effectiveness of the 3D copper foam framework with improved alkaliphilic ability for the development of safe and commercially viable alkali metal anodes.
查看更多>>摘要：The ductility of the Al alloys produced by additive manufacturing (AM) has become a critical property, as the AM Al alloys are increasingly used in the automotive industry. However, the ductility of as-built AM Al alloys is relatively low, even with optimized AM conditions. The post-annealing treatment provides an efficient way to improve ductility. Previous investigation has shown that the annealed AM AlSi3.5Mg2.5 alloy possesses superior ductility. However, the plastic deformation micro-mechanisms of the annealed AM AlSi3.5Mg2.5 alloy remain unclear. In this study, in-situ neutron diffraction was employed to explore the annealed AM AlSi3.5Mg2.5 alloy. The evolutions of phase stresses, dislocation density, and crystallite size in the annealed AM AlSi3.5Mg2.5 alloy during tensile deformation were analyzed. The experimental investigation reveals that the dislocation density in the Al matrix of the annealed AM AlSi3.5Mg2.5 alloy increases slowly in the early plastic deformation stage, and it reaches a saturated level upon the following uniform deformation. The crystallite size decreases quickly in the early deformation stage, and then it decreases slowly. The Kocks-Mecking model and the Voce model can capture the strain hardening behavior well. The determined physical constitutive equations can be applied in continuum mechanical computer simulations.
查看更多>>摘要：A comparative study on the structure and photocatalytic activity of halo-aggregated and differently connected ZrO_2@TiO_2 and TiO_2@ZrO_2 nanocomposites was investigated here towards photodegradation of Alizarin yellow GG model azo dye. The nanocomposites were synthesized by two-step sol-gel method with predominant monoclinic phase for ZrO_2, anatase phase for TiO_2, and characterized through different structural and spectroscopy tools. The photocatalysts with high adsorption capability were however differing in their photodegradation efficiency attributed to varying preferential binding at their interfaces and Zr~(4+) substitution in the TiO_2 lattice. Between the two nanocomposites, superior photocatalytic property was shown by ZrO_2@TiO_2 exhibiting 90-93% degradation efficiency with reproducibility. The growth of titania over zirconia in ZrO_2@TiO_2 reduced the surface states and defects of the core nanocrystal (NC) through strong Zr-O-Ti binding, besides providing shallow traps in smaller TiO_2 NCs that enhanced the separation of photogenerated carriers. The process was also assisted through trapping of holes by surface OH groups on ZrO_2 reducing the carrier migration to TiO_2. The type I heterojunction had favorable positive and negative potentials for valence and conduction bands in ZrO_2 and TiO_2 compared to intermediate superoxide anion and hydroxyl radical generation potentials that catapulted the dye degradation. The interfacial contact in TiO_2@ZrO_2 nanocomposite on the other hand, has been very weak as understood from their absorption and photoluminescence spectra resulting in poorer degradation efficiency. Alizarin yellow GG being a prominent textile azo dye and there are not many reports on its photodegradation, the study also assumes significance in the context of sunlight driven photocatalysis and environmental remediation.
查看更多>>摘要：A simple, economical, and easily scalable high-energy ball-milling method for the synthesis of Li_2GeO_3/ expanded graphite (LGO/EG) as a high-performance anode for lithium-ion batteries is reported. The LGO/EG exhibits a unique architecture with expanded graphite (EG) uniformly coating Li_2GeO_3 (LGO) particles, which effectively inhibited the agglomeration of LGO particles. The LGO/7 wt%EG anode delivers a discharge capacity of 800.6 mA h g~(-1) at 5.0 A g~(-1) with an outstanding capacity retention of 75.9% after 300 cycles at 1.0 A g~(-1) which is 8.3% higher than that of the uncoated LGO anode. This is attributed to the introduction of EG which improves the electronic conductivity of LGO, and the uniformly coated EG can effectively inhibit the volume change of LGO particles during the charging-discharging process. As a result, LGO/EG has outstanding high-rate performance and long-term cycle stability.
NSTL
Elsevier