查看更多>>摘要：? 2022 Elsevier B.V.Urea oxidation reaction (UOR) is an anodic reaction in the electrochemical generation hydrogen and also a crucial half-reaction of direct urea fuel cell (DUFC). However, the scarcity and high cost of noble metals severely limited their application as electrocatalysts for UOR. Herein, we have prepared the composite (Ni@S-C) of nickel nanocrystal embedded in sulfur-doped carbon through facile impregnation method followed by calcination method. X-ray photoelectron spectroscopy (XPS) study indicates the Ni(III) species in Ni@S-C are more positive than typical Ni(III), which serve as the active sites for UOR. Meanwhile, the active Ni(III) is coordinated with S, which facilitates charge transfer and chemisorption of active oxygen species. Under optimal experimental conditions, the Ni@S-C-500 catalyst indicates an excellent UOR activity of 177 mA cm?2 in 1 M KOH + 0.33 M urea at 1.656 V, which was 3.75 times as much as that of the commercial Pt/C catalyst. Meanwhile, the optimal Ni@S-C-500 catalyst also presents a current density (j) retention rate of 80% after 12 h UOR test, which is much higher than that of the commercial Pt/C catalyst (<15% retention). This work provides a strategy for preparing stable and active Ni-based electrocatalyst for the UOR.
查看更多>>摘要：? 2022 Elsevier B.V.Bimetallic metal-organic framework (MOF) has attracted great interest as an electrode for supercapacitors. Most metal sources are limited to valences of + 2 and + 3. We select metal sources of Co (II) and Mo (VI) and demonstrated a crystalline bimetallic MOF precursor prepared by using a facile chemical synthesis. The one-step solvothermal strategy is assisted by thioacetamide (TAA) for the self-assembly Co-Mo-S nanosheet arrays (Co-Mo-S NSAs). TAA-induced etching is essential to regulate the assembly of amorphous structures. Otherwise, only a single-structure crystalline Co-Mo-S could be obtained. The Co-Mo-S NSAs show a large specific capacitance of 1805.28 F g?1 at a current density of 0.5 A g?1. A Co-Mo-S NSAs//AC battery?supercapacitor hybrid (BSH) make with activated carbon as the negative electrode and Co-Mo-S NSAs as the positive electrode. At a current density of 0.5 A g?1, the BSH shows a high energy density of 169.73 Wh kg?1 and a power density of 371.44 W kg?1. After 50,000 cycles, the capacitance retention rate is as high as 94.44%, showing good reversibility and cycle life. This work provides an effective strategy for manufacturing bimetallic MOF-based metal sulfide heterostructure electrode materials for practical energy storage and conversion.
查看更多>>摘要：? 2022Free-standing electrospun carbon nanofibers nonwovens (CNF) with an outstanding cross-linked architecture can be successfully achieved via a simple and practicable strategy by combining electrospinning, stabilization and carbonization. In this study, the hybrids of asphaltene extracted from coal residue liquefaction, polyacrylonitril and terephthalic acid are used as precursors. Due to the synergistic effect of efficient cross-linked structures and short charge transfer channels, flexible cross-linked asphaltene-based CNF (CLACF), as the binder-free supercapacitor electrode, exhibits a high capacity of 225 F g?1 at 0.2 A g?1 and an outstanding rate capability of 148 F g?1 at 100 A g?1. The developed symmetrical supercapacitor based on CLACF has a maximum energy density of 4.20 Wh kg?1 with a power density of 1.22 kW kg?1. It also has excellent cyclic stability with 97.3% capacitance retention after 10,000 cycles at 2 A g?1.
查看更多>>摘要：? 2022 Elsevier B.V.An alternative application of Fe–Cr–Co magnetic alloys as microwave absorption materials was investigated. Fe–25Cr–12Co alloy powder was spinodally decomposed at a starting temperature of 655 ℃, followed by step aging and subsequent controlled cooling to various final aging temperatures. Scanning transmission electron microscopy analysis of the step-aged samples confirmed the occurrence of spinodal decomposition. Composite samples of each step-aged Fe–25Cr–12Co powder mixed with resin were prepared to evaluate their microwave absorption properties in the gigahertz (GHz) band. We found that the imaginary component of the complex permeability for the composites could be tuned by adjusting the final aging temperature. The peak shifted from 0.3 to 3.3 GHz as the final aging temperature was reduced to 500 °C, with a minimum reflection loss of ? 20 dB at 1.6 GHz. The peak shifting was ascribed to the magnetization rotation of single-domain structured ferromagnetic FeCo-rich phase particles, which was induced by the spinodal decomposition of the Fe–25Cr–12Co alloy powder to afford an FeCo-rich phase surrounded by a Cr-rich phase. The single-domain structure of the ferromagnetic FeCo-rich phase particles was generated by an increase in the compositional difference between the FeCo-rich and Cr-rich phases, which arose from controlled cooling to 500 ℃ at a rate of 5 ℃/h and holding at 500 ℃ for 10 h. This promising finding demonstrates the potential advantages of Fe–Cr–Co materials for microwave absorption applications in the GHz frequency range.
查看更多>>摘要：? 2022Recently, MoS2 has been considered as a promising economic and nontoxic thermoelectric material due to its low thermal conductivity and high Seebeck coefficient. However, the poor intrinsic electrical conductivity is still a main obstacle for its wide scale application. Here, we have successfully synthesized p-type V doped MoS2 and systematically investigated the influence of V doping on the thermoelectric properties of MoS2. In the whole doping range, the samples always keep a perfect hexagonal structure. The doped V atoms behave as acceptors and improve the carrier concentration by three to five orders of magnitude, thereby enhancing the electrical conductivity remarkably. In addition, V doping promotes grain refinement and introduces numerous point defects, which play a synergistic role in reducing lattice thermal conductivity. Due to the layered microstructure, obvious anisotropy was observed in the transport properties of VxMo1-xS2. Compared with that of pristine MoS2 (ZTmax = 0.013 at 860 K), the maximum ZT value of VxMo1-xS2 has been increased to 0.24 at 860 K.
查看更多>>摘要：? 2022 Elsevier B.V.Vanadium oxide plays a crucial role as the temperature-sensitive layer of microbolometers. This layer should possess a high temperature coefficient of resistance (TCR) along with a desirable resistivity suitable for readout electronics. Mixed phase vanadium oxide thin films (VxOy) consist of different ratios of pure phases, which affect the resultant resistivity and TCR. It is thus important to be able to control individual phase concentrations to obtain the desired resistivity and TCR. In this study, we show that W-doping does not only introduce a new W-phase but also supports the formation of new V-phases in addition to the change in relative ratios of the original phases. The new V-phase, V2O5, dominates the overall electrical properties. Here, we first present the formation of new phases with W-doping and the structural and electrical characterization with classical tools, and then we show that Terahertz Time-Domain Spectroscopy (THz-TDS) is a strong nondestructive characterization technique that can monitor these effects of doping especially on the electrical behavior of VxOy films. Exploration of the control of this behavior is essential for the fabrication of a high TCR film with a desirable resistivity.
查看更多>>摘要：? 2022 Elsevier B.V.Low-dimensional copper (I)-based ternary metal halides, having the features of nontoxicity, outstanding optical performance and great air-stability, is becoming the promising substitutes for traditional metal perovskite halides. Despite the impressive progress in copper halides, highly effective synthesis of their nanocrystals with precise shape and size control, compared to that of conventional lead halide semiconductors, is still remained to be explored. In this work, we report a systematically optimized finds for the colloidal synthesis conditions of Cs3Cu2Cl5 nanocrystals (NCs). The Cs3Cu2Cl5 NCs are modulated from nanoparticles to nanorods and to nanoplates by adjusting reaction temperature and reaction time. Cs3Cu2Cl5 nanorods give a wide emission at 510 nm, being caused by self-trapped exciton state with exciton binding energy of 137 meV and phonon–electron interaction of 25 meV as determined by temperature-dependent photoluminescence spectra. The photoluminescence quantum yield (PLQY) of the nanorods that were reacted at 150 °C for 1200 s, an optimal reaction condition, reaches up to 80.19%. We also find for the first time that the optical quality of Cs3Cu2Cl5 NCs is positively related to the full width at half maximum of main peak in X-ray diffraction pattern. The findings in this work give a view to the future planning for Cs3Cu2Cl5’s colloidal synthesis and raise an intuitive criterion for the quality of as-synthesized Cs3Cu2Cl5 NCs.
查看更多>>摘要：? 2022 Elsevier B.V.Dispersed NiMo sulfide catalysts were synthesized by hydrothermal deposition method with the assistance of thioglycolic acid (TGA) as sulfiding agent ex situ at 160 °C. The prepared samples were characterized by SBET, XRD, SEM, FTIR, XPS, TPR/TPS, TPD-NH3. The catalyst activity was investigated during hydrodesulfurization (HDS) of thiophene (TH) at 340 °C. XRD and XPS methods showed that this hydrothermal synthesis of Mo and NiMo solids yielded sulfide crystalline phases with high bulk and surface S/Mo ratio. Re-sulfidation of the Ni-containing samples led to an increase in surface area, which was thus able to redisperse the NiMo sulfide active sites. The results of temperature programmed sulfidation measurements combined with mass spectrometric analysis (TPS-MS) of the catalysts revealed the formation of a fraction of TGA species that remained in the pores of the sample with the highest TGA content. In the NiMo catalyst prepared at TGA/Mo molar ratio of four, this TGA enhanced the amount of NiMoS phase in the catalyst and positively affected the HDS activity.
查看更多>>摘要：? 2022 Elsevier B.V.As important electrode materials, 2D layered double hydroxides (LDHs) have attracted much attention owing to their high reaction activity, tunable composition and unique structure. However, the poor cycling stability restricts their large scale industrial applications. To solve this problem, we fabricate several NiCo-LDH nanosheets through regulating the ratio of Ni and Co ions. The as-obtained samples are utilized as cathode for supecapacitor. Thereinto, the NiCo3-LDH product possess a specific capacitance of 699 C g?1 at 1 A g?1. The as-assembled device delivers an energy density of 90.75 W h kg?1 at 2700 W kg?1 and keep 91.84% of its initial capacitance after 10000 cycles. Moreover, as oxygen evolution reaction (OER) electrocatalysts, the obtained product presents an overpotential of 270 mV at 20 mA cm?2 and excellent cycle stability.
查看更多>>摘要：? 2022 Elsevier B.V.Tungsten is facing extremely harsh irradiation environmental challenges as plasma-facing materials. In this work, W-0.3 wt%Y2O3 composites fabricated by nano in-situ composite method were subjected to He plasma irradiation with 60–80 eV and 2.88 × 1022–2.3 × 1026 m?2. The microstructure, morphology, and phase evolution on the surface before and after irradiation were systematically investigated. Besides, the damage behavior and mechanism were initially analyzed. Results show that the nano-scaled Y2O3 with the size of 40–350 nm dispersed uniformly at the grain boundary and within grains of matrix, and part of it formed orientation relationship of [1?11] (1?1?0) W (bcc) // [011] (400) Y2O3 (bcc) with W to significantly improve the phase interface. Surprisingly, there is a semi-coherent relationship between W matrix and Y2O3 phase. Simultaneously, the fine-grained W-0.3Y2O3 composites reveals excellent resistance to He plasma irradiation. As the irradiation dose increases, the surface morphology evolves from smooth to roughening, micro-bulges, rod-shaped and swelling, however, no nano-fuzz are observed when the irradiation dose was up to 2.3 × 1026 m?2. Besides, the chemical constitution and phase composition on surface is unchanged. Moreover, the dislocation lines, loops and rafts are observed by TEM on the surface layer, but no He bubble is formed. The high irradiation resistance may be attributed to the formation channels to release He, which can provide a strategy and idea for designing anti-irradiation W materials.
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