查看更多>>摘要：? 2022 Elsevier B.V.The development of active nonprecious-metal and heteroatom-doped materials is critical for the oxygen evolution reaction (OER). Herein, asphaltene-derived carbon-coated Fe- and N-doped hierarchical hollow porous carbon microtubes were prepared through feasible freeze-drying and carbonization/activation strategies. Cotton with a fibrous morphology acted as a soft template and carbon precursor, while asphaltene with easy graphitization properties was utilized to stabilize the structure of microtubes and accelerate the charge conductivity. Meanwhile, Fe- and N-doping changed the electronic structure of carbon and increased the number of active sites. In particular, the optimum sample displayed excellent OER activity with a lower overpotential of 261.4 mV at 10 mA/cm2 and Tafel slope of 94.60 mV/dec under alkaline conditions. Moreover, the catalyst demonstrated excellent long-term durability with a 10% attenuation rate after continuous operation for 50 h by the chronoamperometry method at a constant potential of 1.5 V. This work provides a strategy for the effective resource utilization of biomass and asphaltene to prepare highly efficient OER electrocatalysts.
查看更多>>摘要：? 2022 Elsevier B.V.A heterostructured polypyrrole@magnetic Co/CoFe2O4 nanoparticles@hollow nanobowl-like carbon (PPy@Co/CoFe2O4@HNBC) composite with a layer-by-layer (LBL) structure based on HNBC was prepared via a facile three-step process. HNBC was synthesized by a typical template method, then sequentially decorated with Co/CoFe2O4 and PPy via in-situ growth and polymerization. The relationship between the structure, components, and electromagnetic wave (EMW) absorption performance of PPy@Co/CoFe2O4@HNBC was studied in depth. The EMW absorbing research shows that PPy@Co/CoFe2O4@HNBC exhibits excellent EMW absorption capability, with a minimum reflection loss (RLmin) of up to ?61.85 dB at 12.80 GHz and 1.90 mm and a widest effective absorption bandwidth (WEAB, RL≤?10.00 dB) value of 5.60 GHz at 1.70 mm. The excellent EMW absorption performance of PPy@Co/CoFe2O4@HNBC can be ascribed to the multiple reflection and scattering that occurs due to its unique microstructure and the synergistic effects between the polarization and conduction induced dielectric loss, and the natural resonance and exchange resonance induced magnetic loss. As a consequence, the PPy@Co/CoFe2O4@HNBC composite designed in this work is a hopeful candidate for application in the field of EMW absorption.
查看更多>>摘要：? 2022 Elsevier B.V.For the first time, a new structure of Ta2Ni3S8, one of the family systems of M2N3X8, a recently studied one-dimensional chalcogenide material, was synthesized. Unlike Ta2Ni3S8 in the orthorhombic phase, which is known to have semiconductor properties, Ta2Ni3S8 in the tetragonal phase displayed metallic material properties. Structural analysis through X-ray diffraction confirmed that the tetragonal Ta2Ni3S8 (T-Ta2Ni3S8) had the same structure as the tetragonal Ta2Ni3Se8 (T-Ta2Ni3Se8), a material with an S- and Se- substitution; the only difference was the lattice constant. Additionally, different elemental analyses were used to confirm that the ratio of Ta:Ni:S elements was 2:3:8. This study is significant as basic research that can be applied to various electronic devices by applying bandgap tuning and lattice-matched electrode design based on M2N3X8 family material.
查看更多>>摘要：? 2022 Elsevier B.V.The very high specific discharge capacities of Ni> 90% cathodes are often undone by their extremely poor cycle life and thermal stability. Herein, Ni-poor, and Al-rich particle with double concentration gradients is fabricated by synthesizing particles of the Ni-rich hydroxide Ni0.9Co0.1(OH)2 in a highly efficient Taylor flow (TF) reactor and then depositing Al onto their surfaces using three methods: spray-drying and conventional wet and dry chemical coating. The uniformity of the surface distribution of Al on the Ni-rich transition metal oxide cathode materials affected the overall structural and electrochemical stability. Among our three systems, the cathode material prepared with the spray-dried Al exhibited the best performance, with an initial discharge capacity of 196.9 mA h g–1 and capacity retention of 93% after 100 cycles at a rate of 1 C. It also demonstrated superior electrochemical performance at higher C-rates. For example, at 10 C, it delivered an initial discharge capacity of 134.4 mA h g–1, compared with 56.8 mA h g–1 for the Al-free LiNi0.9Co0.1O2. We attribute this enhanced electrochemical performance to the presence of Al and its uniform distribution (through spray-drying processing) on the outer layer of the active material, with the Ni and Co elements remaining mainly within the core.
查看更多>>摘要：? 2022Microwave absorption performances can be remarkably enhanced using an electromagnetic (EM) wave absorber with synergistically dielectric and magnetic losses. In this study, the eggplant was used as a raw material to produce silicon carbide (SiC) aerogel by two steps: carbonization and subsequent carbothermic reduction. Then the magnetic NiCo layer was coated on the SiC aerogel (NiCo–SiC) by chemical plating method. The NiCo-SiC aerogel with an extremely low density (0.194 g/cm3) primarily composed of a porous SiC skeleton, SiC nanowires, and the magnetic NiCo alloy nanoparticles distributed on SiC skeleton and nanowires surfaces. The existence of magnetic NiCo alloy nanoparticles in the aerogel, the magnetic and dielectric losses are both increased by the formed heterogeneous interfaces. Thus, the NiCo–SiC aerogel with a thickness of 3 mm exhibits a minimum reflection loss (RLmin) of ? 44.5 dB and an effective absorption bandwidth (RL<?10 dB) of 7.6 GHz, which displays the potential application in lightweight and excellent EM wave absorbers.
查看更多>>摘要：? 2022 Elsevier B.V.Novel corrugated fins were proposed and applied in metal hydride devices in this paper. To simulate the hydrogen absorption process, we first validated the numerical models based on the finite element method. Then we investigated the effect of device geometry and turbulent flow of cooling water on the absorption performance. The optimized device with 5 mm fin height, 2 mm fin length and 13 fins was obtained, and the absorption time for 0.8 wt% saturation level was reduced by 32% compared with the traditional device with circular fins. It is found that the turbulent flow of cooling water has a great effect on enhancing the hydrogenation rate, and critical Reynolds number is 11,860. The heat transfer resistance drops from 0.140 K/W to 0.023 K/W when Reynolds number increases from 1780 to 11,860. Furthermore, the optimal turbulence modeling strategy was analyzed in detail. The predictions derived from the L-VEL model with wall distance initialization are far more accurate than those of other turbulence models and have the lowest computational time of 2118 s. Our new device is easy to be manufactured and has great potential for various alloy loads as well.
查看更多>>摘要：? 2022A new approach was proposed to construct a novel 3D hybrid nanocomposite heterostructure GO/MnCo2O4/Ni-V-Se as a hybrid supercapacitor electrode. Electrons can easily migrate from Mn ions to Ni ions, thereby increasing the electron energy of the metal orbital, and this inductive effect can effectively improve the electron transfer efficiency. In addition, the application of surface/interface control method also enables this electrode material to exhibit unique advantages. In this heterostructure, graphene serves as the extended conductive framework, cube-like MnCo2O4 and flower-like Ni-V-Se spheres derived from MOFs as spacers separate the sheets to avoid the layer-by-layer stacking of graphene. Complemented by Ni-V-Se coating, the formed composite heterostructure exhibits excellent electrochemical performance. The as-prepared GO/MnCo2O4/Ni-V-Se delivers ultra-high specific capacity (1292.3 C·g?1 at 1 A·g?1), rate capability (94.87%) and cycling stability. Finally, the hybrid supercapacitor assembled by GO/MnCo2O4/Ni-V-Se and activated carbon also shows good electrochemical performance.
查看更多>>摘要：? 2022 Elsevier B.V.Dy3+-doped luminescent glasses have received great attention due to their ability to emit white light at a suitable yellow-to-blue intensity ratio. However, achieving bright white light using single Dy3+-doped glasses remains a challenge due to the hypersensitivity of the emission band at 575 nm — usually resulting in intense yellow emission. In this work, we present a novel approach for compensating for the blue emission deficiency of Dy3+ to produce resin-free white light-emitting diodes (WLEDs) by synthesizing two series of Dy3+-doped glasses from tellurite and silicate systems on which blue-emitting carbon dots (BCDs) are spin-coated. The structural, chemical, optical, and luminescence properties of tellurite and silicate glasses are compared and discussed in detail. White light emissions are obtained upon 365-nm excitation for BCD-coated Dy3+-doped tellurite and silicate glasses with color coordinates of (x = 0.31, y = 0.33) and (x = 0.31, y = 0.34) and correlated color temperatures (CCT) of 5518 K and 5316 K, respectively. BCDs coating increases photoluminescence quantum yield (PLQY) values from 3.10 % to 5.62 % and from 20.81 % to 31.49 % for tellurite and silicate glasses, respectively. Ultimately, the findings in this work show the potential of BCD-coated luminescent glasses with excellent luminescent properties to be considered in solid-state lighting applications.
查看更多>>摘要：? 2022Designing electrodes with structures suitable for storing and fixing sulfur to overcome the inherent shortcomings of lithium-sulfur (Li–S) batteries is an effective approach to achieving commercial application. Indeed, multifunctional electrodes constructed with sulfur immobilization substrate and efficient catalyst has dramatically improved the utilization of sulfur. However, structurally designing the substrate and achieving uniform dispersion of catalytic remain huge challenges. In this paper, a metal-organic frameworks derived flower shaped nitrogen doped carbon (NC) materials anchored with core-shell Ni-NiO nanoparticles loaded on carbon paper (CP) was fabricated, which equipped with 3D conductive network and hierarchical porous structure physically restrict polysulfide shuttling. Furthermore, well-proportioned Ni-NiO nanoparticles were induced into host to bond with polysulfides further catalyzed the electrochemical reaction. Notably, the S@Ni-NiO@NC/CP exhibited high specific capacity with 1332.9 mAh/g initial specific capacity at 0.5 C and maintained at 896.3 mAh/g after 200 cycles. And S@Ni-NiO@NC/CP can achieves an initial capacity of 1095.7 mA h g?1 even with high sulfur loading of 4.6 mg/cm2. Electrochemical test results indicated that the introduction of Ni-NiO catalyst can improve the kinetics and reduce the reaction overpotential (ηE), and further affects the value of concentration overpotential (ηC) ultimately leads to the increase of battery capacity.
查看更多>>摘要：? 2022 Elsevier B.V.Deep understanding and powerful control of the magnetization dynamics is of great importance for developing high speed spintronic devices. In this work, laser-induced ultrafast demagnetization process of Gdx(CoFe)1-x alloy films has been extensively studied by using the fs-laser pump-probe technique. Interestingly, it is found that by adjusting the Gd content x and hence the intersublattice 3d-4f exchange coupling strength, the demagnetization dynamics varies from a fast one-stage decay to a continuous or a discrete two-stage decay, which is mainly resulted from the different energy transfer rates via the intersublattice exchange coupling and has been well simulated by considering the Elliott-Yafet type spin-flip scattering theory and the 4-Temperature model. Moreover, we observed that the second-stage decay time is strongly dependent on the external magnetic field, which is analyzed theoretically and suggests an origin of ultrafast giant magnetic cooling effect via the modulation of lattice-spin coupling. These studies are quite helpful for achieving the efficient manipulation of ultrafast magnetization behaviors.
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