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W atoms/clusters are employed to in situassist the development of layered vertically aligned carbon nanotube arrays (VACNTs) through hot-filament-assisted chemical vapor deposition (HFCVD) with liquid binary Fe3O4/AlOxcatalysts. The hot W filament was utilized to in situevaporate atomic W and form W clusters on Fe catalysts, which have a strong impact on the growth of layered VACNT arrays. The migration and Ostwald ripening of Fe catalysts are found to be suppressed immediately with more W clusters deposition during CNT growth. Through controlling the deposition of W clusters, the electrochemical energy storage performance of as-prepared layered VACNT arrays is also tunable as electrodes of ion-based supercapacitors. The layered VACNT arrays can achieve a high capacity of 83.1 mF cm–2and possess desirable rate performance due to the suitable hot filament condition (55 W for 90 s). This work provides a new perspective to in-depth understand the behavior of W filament during HFCVD and the significant role of the in situgenerated W clusters on the growth of CNTs by maintaining the catalytic activity and structure of catalysts.

Developing high-performance Li-S batteries with high sulfur loading is highly desirable for practical application and remains a major challenge. To achieve this goal, the following requirements for designing carbon/metal compound composites need to be met: (i) the carbon materials need to exhibit suitable specific surface area, void structure, and electrical conductivity; (ii) the weight content of the metal compounds should be low; and (iii) the metal compounds need to show a strong adsorption and efficient electrocatalytic function for LiPSs. In this study, inspired by the body structure of an octopus, a new carbon/NiS2hierarchical composite is reported, in which the apical NiS2nanoparticles (0D) on a 1D carbon nanotubes (CNTs) are supported on a three-dimensional carbon (3DC) framework (3DC-CNTs-NiS2). The 3DC-CNTs-NiS2composite has a high specific surface area (271 m2g–1), good electrical conductivity, and low NiS2content (9.2 wt %), and the apical NiS2nanoparticles are capable of adsorption and electrocatalysis toward LiPSs, demonstrated by both electrochemical characterization and theoretical calculation. When used as a cathode host of the Li-S battery, it exhibits an ultra-stable cycling performance with a fade rate of 0.043% per cycle over 1000 cycles; even with a high S loading (6.5 mg cm–2with 90 wt % of S), the soft package battery delivers a high area capacity of 5.0 mAh cm–2under the E/S ratio of 5 μLEmg–1s. This work provides a new approach to design and fabricate multi-functional S hosts with high S loading.

Ceramic phase reinforced aluminum matrix composites (CAMCs) are widely used in high-tech fields represented by aerospace industry due to their advantages of high specific strength, high specific modulus, high thermal stability, and light weight. Strong interface bonding is a prerequisite for high performance of multiphase materials. Herein, a novel CAMC in situ reinforced by MgAl2O4particles and MgAlB4nanorods was prepared by vacuum hot-pressing combined with hot-extrusion process. A high-resolution transmission electron microscope was used to characterize the orientation relationship and interface structure between the ceramic phases and the aluminum matrix. Two orientation relationships (OR1 and OR2) of MgAl2O4/Al and one (OR3) of MgAlB4/Al are determined: OR1-[011]p//[011]Al, (11̅1)p//(11̅1)Al; OR2-[211]p//[011]Al, (113̅)p//(022̅)Al; OR3-[101̅0]R//[001]Al, (0002)R//(2̅20)Al. The MgAl2O4in OR1 forms a coherent interface with the aluminum matrix at (111) surface, while they form a 4 × 5 near coincidence site lattice (CSL) interface structure for OR2. In OR3, the MgAlB4forms an approximate coherent interface with Al matrix at its (0002) surface and a 2 × 5 CSL interface structure at its (011̅0) surface. First-principles calculations suggest that MgAl2O4combines to aluminum at (111) plane through covalent bonds, which means high interfacial bonding strength. The hot-extrusion process makes the ceramic phase evenly distributed in the matrix. The mechanical properties of the composites are greatly improved compared with pure aluminum.

A series of NiCo2P-based electrocatalysts, which were wrapped by CeO2whose oxygen vacancies (VO) are partially filled with phosphorus atoms (named as NiCo2Px/PxFVo-CeO2, where xrefers to the consumption of NaH2PO2·H2O), have been fabricated to improve the electrocatalytic reactivity of NiCo2P toward hydrogen evolution in alkaline solution. In the novel catalysts, the P atoms fill the oxygen vacancies, elevate the chemical valence state of Ni2+and Co3+, and increase the hydride acceptors, which reinforcing the promoting effect of CeO2in the hydrogen evolution reaction (HER). Moreover, the negatively charged P atoms capture the positively charged protons more easily, benefiting the Volmer step during HER. Furthermore, the synergistic effect between oxygen vacancies and the filled P atoms accelerates the migration rate of electrons/ions and increases the electrochemical active area. All of the above are advantageous to the hydrogen evolution of NiCo2Px/PxFVo-CeO2in alkaline electrolyte. As a result, the overpotential as low as 33.6 mV is achieved for NiCo2P0.3/P0.3FVo-CeO2in alkaline media to drive a current density of 10 mA cm–2. The reactivity is superior to that of Pt/C at a large current density along with a Tafel slope of 61.24 mV dec–1and long-term durability, which giving a new technology for efficient transition-metal catalyst candidates toward HER in alkaline solution.

A flexible one-pot strategy for fabricating a 3D network of nitrogen-doped (N-doped) carbon ultrathin nanosheets with closely packed mesopores (N-MCN) via an in situtemplate method is reported in this research. The self-assembly soluble salts (NaCl and Na2SiO3) serve as hierarchical templates and support the formation of a 3D glucose–urea complex. The organic complex is heat-treated to obtain a 3D N-doped carbon network constructed by mesoporous nanosheets. Especially, both the mesoporous structure and doping content can be easily tuned by adjusting the ratio of raw materials. The large specific surface area and closely packed mesopores facilitate the lithium ion intercalation/deintercalation accordingly. Besides, the nitrogen content improves the lithium storage ability and capacitive properties. Due to the synergistic effect of hierarchical structure and heteroatom composition, the 3D N-MCN shows excellent characteristics as the electrode of a lithium ion battery and supercapacitor, such as ultrahigh reversible storage capacity (1222 mAh g–1at 0.1 A g–1), stable long cycle performance at high current density (600 cycles at 2 A g–1), and high capacitive properties (225 F g–1at 1 A g–1and 163 F g–1at 50 A g–1).

High-quality microsized ultrathin single-crystalline anatase TiO2nanosheets (MS-TiO2) with exposed {001} facets were synthesized by a facile and low-cost two-step process that combines a graphene oxide (GO)-assisted hydrothermal method with calcination. Both GO and HF play an important role in the formation of well dispersed MS-TiO2. As a novel microsized (1–4 μm) ultrathin two-dimensional (2D) material, MS-TiO2possesses much higher lateral size and aspect ratio compared to common 2D nanosized (30–60 nm) ultrathin TiO2nanosheets (NS-TiO2), resulting in excellent electronic conductivity and superior electron transfer and diffusion properties. Here, we fabricated MS-TiO2and NS-TiO2, both of which were incorporated with the TiO2nanoparticles (P25) to constitute the hybrid photoanode of dye-sensitized solar cells (DSSCs), and explored the effect of the lateral size (nano- and micro-) of ultrathin TiO2nanosheets on their electron transfer and diffusion properties. Benefiting from the faster electron transfer rate and short diffusion path of the MS-TiO2, the MS-TiO2/P25 gains the more superior performance compared to pure P25 and NS-TiO2/P25 in the application of DSSCs. Moreover, it is expected that the novel high aspect ratio MS-TiO2may be applied in diverse fields including photocatalysis, photodetectors, lithium-ion batteries and others concerning the environment and energy.

Poor rate capability and cycling performance are the major barriers to the application of lithium rich layered oxides (LLOs) as the next generation cathodes materials for lithium-ion batteries. In this paper, a novel surface double phase network modification has been applied to enhance the rate property of Li1.2Co0.13Ni0.13Mn0.54O2(LR) via flexible electrostatic heterocoagulation and thermal treatment. The template action of multiwalled carbon nanotubes (MWCNTs) network on LR clusters results in the spinel phase network formation at the interface between the LR and MWCNTs. The phase transformation process from layered component toward spinel phase is identified through the detailed investigation of the interface using high-resolution transmission electron microscopy, fast Fourier transformation, and the detailed analysis on the transformation of simulated diffraction patterns. The double phases stretch two sets of networks with both fine Li ion and electron conductivity onto and within the clusters of LR, lowering the surface resistance, reducing the electrochemical polarization, and as a result, significantly enhancing the rate capability of LR. The double phase network modification, combining MWCNT coagulation and spinel phase modification, has profound potential in accelerating kinetics for LLOs.

Graphene/metal-oxide nanocomposites have been widely studied as anode materials for lithium ion batteries and exhibit much higher lithium storage capacity beyond their theoretical capacity through mechanisms that are still poorly understood. In this research, we present a comprehensive understanding in microscale of the discharge process of graphene/TiO2containing surface, bulk, and interfacial lithium storage based on the first-principles total energy calculations. It is revealed that interfacial oxygen atoms play an important role on the interfacial lithium storage. The additional capacity originating from surface and interfacial lithium storage via an electrostatic capacitive mechanism contributes significantly to the electrode capacity. The research demonstrates that for nanocomposites used in energy storage materials, electrode and capacitor behavior could be optimized to develop high-performance electrode materials with the balance of storage capacity and rate.

Highly ordered hierarchical TiO2nanostructures involving primary honeycomb and secondary nanoparticles and nanowires are prepared by a two-step facile process. The TiO2nanotube arrays grow first on Ti foil through anodization. After the wet-chemical reaction of the TiO2nanotube arrays with alkaline and acid solution in turn, the hierarchical nanostructures wire-in-honeycomb and porous honeycomb are obtained by a dissolution–coagulation and dissolution–adsorption mechanism, respectively. The power conversion efficiency of the hierarchical TiO2honeycomb nanostructures for the dye-sensitized solar cells (DSCs) shows a significant improvement, as high as 5.73%, increased by 1.42 times compared with that of TiO2nanotube arrays. The performance improvement of DSCs based on the hierarchical nanostructures is attributed to the increase in the specific surface area.