查看更多>>摘要:? 2022V2CTx MXene shows excellent potential in lithium-ion batteries (LIBs) due to its unique two-dimensional structure and rich surface chemistry. However, the low Li+-storage capacity contributed by the innate low conductivity seriously hinders its commercial application. Herein, Ag nanoparticles are grafted on the V2CTx MXene by a one-step reduced silver nitrate (AgNO3). The obtained Ag nanoparticles are directly reduced from AgNO3 by the -OH terminations of V2CTx MXene, which promote the conductivity of V2CTx/Ag. Besides, the Ag nanoparticles in the layered body structure have excellent structural strength, which boost the whole durability of the LIB by inhibiting the aggregation of V2CTx MXene. Further, the dependence of the battery performances on the Ag contents is investigated. We find that the most favorable Ag content is 4.0 at% which can simultaneously favor the transferability of electron and ion and the electrochemical kinetics to the most considerable extent. The V2CTx/Ag-40 achieves a specific capacity of 631 mAh g?1 at 0.05 A g?1 after 50 cycles, and even maintains a specific capacity of 298 mAh g?1 at 5 A g?1 after long-term 2000 cycles. The adopted in situ reduction strategy and the excellent electrochemical property of V2CTx/Ag nanostructure may be relevant for future anode material in LIBs.
查看更多>>摘要:? 2022 Elsevier B.V.With the rise of two-dimensional (2D) materials, layered metal thiophosphates (MPS3), as an important branch, have attracted much attention because of their excellent physical and chemical properties. Cadmium phosphorus trisulfide (CdPS3), as a promising photocatalyst, can be used for hydrogen evolution and organic degradation. Herein, high-quality 2D CdPS3 few layers are obtained by exfoliating bulk CdPS3 crystal. The optical properties of the as-obtained CdPS3 few layers show good light-harvesting ability, endowing it with excellent photocatalytic hydrogen evolution performance (10.88 mmol g?1 h?1) and high organic degradation performance (more than 92% within 30 min) under Xe lamp irradiation. This research provides opportunities for the preparation and application of other 2D MPS3 type materials in the field of photocatalysis.
查看更多>>摘要:? 2022 Elsevier B.V.A metallic glass of nominal composition Mg75Ni20Mm5 (Mm: mischmetal) when heated shows primary crystallization to Mg2Ni. Transmission electron microscopy studies, including annealing experiments in-situ, supported by differential scanning calorimetry and X-ray diffraction, reveal the remarkable complexity of this crystallization. The crystals are lens-shaped and at constant temperature show linear (constant-rate) growth, despite marked partitioning of nickel from the glass to the crystal. The growth, constrained by atomic rearrangement at the glass-crystal interface, gives a crystalline phase that is partially disordered and has almost half of its magnesium sites vacant. The combination of solute partitioning and isothermal linear growth challenges usual assumptions about the characteristics of primary and polymorphic crystallization. This hybrid behavior is interpreted in terms of the widely differing diffusivities of the atomic species in this system.
查看更多>>摘要:? 2022 Elsevier B.V.The electronegative element-filled skutterudite (EN-SKD) has become an interesting thermoelectric material in the mid-temperature region in recent years. However, the strong intrinsic excitation above ~650 K affects its thermoelectric performance, limiting the practical applications in thermoelectric generators (TEG). To alleviate this situation, a series of EN-SKD compounds with different Ni substitutions, Se0.05NixCo4-xSb12 (x = 0.1, 0.2, 0.3, 0.4) are fabricated by solid-state reaction. It is found that the substitution of Ni for Co significantly suppresses the bipolar effect as the temperature above ~700 K due to the increase of electron concentration, reduces the lattice thermal conductivity (κL) by introducing phonon scattering centers, and consequently performs a significant enhancement of zT. Se0.05Ni0.4Co3.6Sb12 realizes a zT value two times higher than Se0.05Ni0.1Co3.9Sb12 at 823 K. This work demonstrates an approach to optimize thermoelectric performance by Ni substitution at Co sites in EN-SKD through the suppression of the bipolar effect on S and κ.
查看更多>>摘要:? 2022 Elsevier B.V.The high capacity of silicon (Si) for lithium incorporation makes it a promising anode material for lithium-ion batteries; however, pulverization of Si due to huge volume changes during lithiation/delithiation leads to significant capacity loss during cycling. To address challenges in low cyclability, nanostructured Si in carbon nanocomposites offers an attractive solution. In this study, we report an efficient method for the synthesis of a nanocomposite containing Si nanoparticles homogeneously embedded in an electrically conductive carbon nanofiber (CNF) network. Electrospinning of polyacrylonitrile (PAN) solution containing hydrolyzed tetraethyoxysilane (TEOS), as a Si precursor, and subsequent carbonization of hybrid nanofibers yielded a composite of SiO2 ultrafine nano-domains in the carbon network (C-SiO2). Low temperature molten salt-assisted aluminothermic reduction of C-SiO2 nanofibers allowed us to produce a C-Si/SiOx nanocomposite without forming detrimental SiC, which is thermodynamically favorable at high temperatures in a system with a high interfacial surface area between the carbon and SiO2 phases. The nanocomposite C-Si/SiOx anodes showed a reversible capacity of 860 mAh g?1 at a current rate of 200 mA g?1, retaining a capacity of 680 mAh g?1 after 100 cycles. In addition, the nanocomposite anodes delivered a reversible capacity of 569 mAh g?1 at a current rate of 400 mA g?1 while maintaining 95% of maximum capacity after subsequent 100 cycles. This study demonstrates the capability of designing nanocomposite anodes from reaction precursors combined with low-temperature aluminothermic reduction to produce a capacity-retaining anode composite of Si nanocrystals uniformly dispersed in the carbon matrix.
查看更多>>摘要:? 2022 Elsevier B.V.As an important branch of functional materials, ferroic materials, especially ferroelectrics have attracted increasing attention in decades. Because of the rising demand in industry, performances on single-phase-based ferroelectric materials seems to meet the bottleneck, studies on composites are becoming urgent now. Motivated by this, structure designing of composite materials was considered as a key factor for pursing better properties, yielding fruitful research work. Among those work, interfacial parts between different phases was always reported to play significant roles in such composite ferroelectrics, and the authors summed them up as the strategy of INTERFACE ENGINEERING. Being different from traditional reviews, which mostly introduce materials with certain system or function, this one focuses more on the utilizing of interfaces in different states of ferroelectrics such as: Tuning magnetoelectric coupling coefficient by terminated layer in epitaxial thin films; broadening Curie Temperature range by inducing interfacial stain; enhancing dielectric tunability by forming topological structures; increasing electrical breakdown strength introducing artificial interfaces, etc. Besides, deeper mechanisms of such performance optimizations were also digged out and explained, hoping to offer new ideas for exploiting the next-generation electronic materials and devices.
查看更多>>摘要:? 2022 Elsevier B.V.Using hierarchically structured TiO2 as scaffolding to construct heterojunctions has been proven to be an efficient method for enhancing photocatalytic activity. In this study, 0D/3D hierarchical Ag3PO4/TiO2 photocatalysts were prepared using an improved hydrothermal-induced solvent-confined assembly and an in-situ fabrication method. The SEM results suggest that with an increasing amount of Ag3PO4, an increasing number of agglomerated Ag3PO4 particles were detected. As a result, Ag3PO4/TiO2-1 exhibited the highest photocatalytic activity and decomposed 96.5% methylene blue in 9 min or 94.6% of rhodamine B in 12 min. A practical application of water remediation in four real water bodies for coexisting dyes was also performed. The remarkable photocatalytic activity of the obtained Ag3PO4/TiO2 composites can be attributed to the suitable size of Ag3PO4, unique hierarchical porous nature, and high efficiency of the photoinduced carrier separation and transfer. The proposed photocatalytic mechanisms and charge transfer pathways in heterojunction photocatalysts were investigated using valence-band X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, Mott–Schottky analysis, and scavenging experiments. These results illustrate the formation of a type-II heterojunction between Ag3PO4 and TiO2. This study provides novel insights into the design and construction of heterojunction photocatalysts for the decomposition of organic pollutants.
查看更多>>摘要:? 2022 Elsevier B.V.The development of low-Pt catalysts is important for the large-scale application of Pt-based catalysts. Catalytic reactions mainly occur on the surface or interface of a material, and thus the surface properties of the catalyst will strongly affect their catalytic activity; this phenomenon has attracted widespread attention. Here, a series of Pt NPs with different chemical states and particle sizes were obtained by changing the light source wavelength, light time, and other conditions of light deposition synthesis. The Pt-TiO2 catalyst has excellent potential in both photocatalytic hydrogen evolution (4.5 mmol·g?1·h?1) and electrocatalytic hydrogen evolution (26 mV@10 mA cm?2). We also found that the photocatalytic activity is more sensitive to the chemical state of Pt and that reducing the catalyst size can improve the electrocatalytic activity. This work not only provides a green and effective method to adjust the chemical state of precious metals on metal oxides but also helps to understand the impact of surface states on the catalytic process.
查看更多>>摘要:? 2022 Elsevier B.V.In the present study, lightweight high-strength Ti-V-Al based high temperature shape memory composites were fabricated to broaden the application of shape memory alloys. In-situ TiB whiskers and La2O3 particles were introduced and the distribution of reinforcements was optimized by the combination of low-energy milling, hot-press sintering and subsequent hot rolling. The in-situ reinforcements formed a network structure, which evolved from an equiaxed shape to an ellipsoidal shape. Furthermore, the direction of the reinforcement was inclined to the rolling direction. In the reinforcement-lean area, the phase constitution evolved from the β parent phase to the α″ martensite phase, and the width of the α″ martensite gradually widened with increasing distance to the in-situ reinforcements. The composites maintained high martensitic transformation temperature characteristics. Excellent mechanical properties with a high tensile strength of 885 MPa and a large elongation of 13.1% are obtained in the composite with a 1.0 wt% LaB6 addition and 70% deformation ratio. Meanwhile, the composite realized 3.49% recoverable strain under 6% pre-strain conditions.
查看更多>>摘要:? 2022 Elsevier B.V.Two-step selenization process has been proved to control Cu2ZnSn(S,Se)4 (CZTSSe) crystallization growth, helping to fabricate a homogeneous large-grain structure of CZTSSe absorber. The two-step selenization process is usually composed of the low-temperature nucleation (LT) and high-temperature grain growth reaction (HT) processes. Here, an exploration of optimizing the annealing conditions at each step in the two-step process is reported to obtain the excellent structure of ionic liquid solution based Cu2ZnSn(S,Se)4 absorber, boosting performance of the solar cell. Based on the basic requirement of an absorber candidate for solar cells (the compact films), three effective kinds of two-step process are confirmed (LT400–10&HT540–10, LT400–10&HT550–10, and LT400–10&HT560–10). We further explore the other properties of sample prepared by one-step and these three kinds of two-step process, respectively, and the optimal two-step process can be identified as LT400–10&HT550–10, which also confirms a homogeneous large-grain structure of CZTSSe absorber. Finally, CZTSSe solar cell with the highest efficiency of 9.24% can be achieved, which can be improved 67% than one by one-step annealing process (5.54%).